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  • 1.
    Alinejad, M.
    et al.
    Department of Forestry, Michigan State University, East Lansing, United States.
    Henry, C.
    Department of Forestry, Michigan State University, East Lansing, United States.
    Nikafshar, S.
    Department of Forestry, Michigan State University, East Lansing, United States.
    Gondaliya, A.
    Chemical Engineering and Materials Science, Michigan State University, East Lansing, United States.
    Bagheri, B.
    Chemical Engineering and Materials Science, Michigan State University, East Lansing, United States.
    Chen, N.
    Eastern Regional Research Center, USDA-ARS, Wyndmoor, United States.
    Singh, S.K.
    Chemical and Biological Engineering, Montana State University, Bozeman, United States.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Nejad, M.
    Department of Forestry, Michigan State University, East Lansing, United States. Chemical Engineering and Materials Science, Michigan State University, East Lansing, United States..
    Lignin-based polyurethanes: Opportunities for bio-based foams, elastomers, coatings and adhesives2019In: Polymers, ISSN 2073-4360, E-ISSN 2073-4360, Vol. 11, no 7, article id 1202Article in journal (Refereed)
    Abstract [en]

    Polyurethane chemistry can yield diverse sets of polymeric materials exhibiting a widerange of properties for various applications and market segments. Utilizing lignin as a polyol presentsan opportunity to incorporate a currently underutilized renewable aromatic polymer into theseproducts. In this work, we will review the current state of technology for utilizing lignin as a polyolreplacement in different polyurethane products. This will include a discussion of lignin structure,diversity, and modification during chemical pulping and cellulosic biofuels processes, approachesfor lignin extraction, recovery, fractionation, and modification/functionalization. We will discussthe potential of incorporation of lignins into polyurethane products that include rigid and flexiblefoams, adhesives, coatings, and elastomers. Finally, we will discuss challenges in incorporating ligninin polyurethane formulations, potential solutions and approaches that have been taken to resolvethose issues.

  • 2. Andersson, Christian
    et al.
    Helmerius, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Hodge, David
    Berglund, Kris
    Rova, Ulrika
    Inhibition of succinic acid production in metabolically engineered Escherichia Coli by neutralizing agent, organic acids, and osmolarity2009In: Biotechnology progress (Print), ISSN 8756-7938, E-ISSN 1520-6033, Vol. 25, no 1, p. 116-123Article in journal (Refereed)
    Abstract [en]

    The economical viability of biochemical succinic acid production is a result of many processing parameters including final succinic acid concentration, recovery of succinate, and the volumetric productivity. Maintaining volumetric productivities >2.5 g L-1 h(-1) is important if production of succinic acid from. renewable resources should be competitive. In this work, the effects of organic acids, osmolarity, and neutralizing agent (NH4OH, KOH, NaOH, K2CO3, and Na2CO3) on the fermentative succinic acid production by Escherichia coli AFP184 were investigated. The highest concentration of succinic acid, 77 g L-1. was obtained with Na2O3. In general, irrespective of the base used, succinic acid productivity per viable cell was significantly reduced as the concentration of the produced acid increased. Increased osmolarity resulting from base addition during succinate production only marginally affected the productivity per viable cell. Addition of the osmoprotectant glycine betaine to cultures resulted in an increased aerobic growth rate and anaerobic glucose consumption rate, but decreased succinic acid yield. When using NH4OH productivity completely ceased at a succinic acid concentration of similar to 40 g L-1. Volumetric productivities remained at 2.5 g L-1 h(-1) for tip to 10 h longer when K- or Na-bases where used instead of NH4OH. The decrease in cellular succinic acid productivity observed during the anaerobic phase was found to be due to increased organic acid concentrations rather than medium osmolarity.

  • 3. Andersson, Christian
    et al.
    Hodge, David
    Berglund, Kris
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Rova, Ulrika
    Effect of different carbon sources on the production of succinic acid using metabolically engineered Escherichia coli2007In: Biotechnology progress (Print), ISSN 8756-7938, E-ISSN 1520-6033, Vol. 23, no 2, p. 381-388Article in journal (Refereed)
    Abstract [en]

    Succinic acid (SA) is an important platform molecule in the synthesis of a number of commodity and specialty chemicals. In the present work, dual-phase batch fermentations with the E. coli strain AFP184 were performed using a medium suited for large-scale industrial production of SA. The ability of the strain to ferment different sugars was investigated. The sugars studied were sucrose, glucose, fructose, xylose, and equal mixtures of glucose and fructose and glucose and xylose at a total initial sugar concentration of 100 g L-1. AFP184 was able to utilize all sugars and sugar combinations except sucrose for biomass generation and succinate production. For sucrose as a substrate no succinic acid was produced and none of the sucrose was metabolized. The succinic acid yield from glucose (0.83 g succinic acid per gram glucose consumed anaerobically) was higher than the yield from fructose (0.66 g g-1). When using xylose as a carbon source, a yield of 0.50 g g-1 was obtained. In the mixed-sugar fermentations no catabolite repression was detected. Mixtures of glucose and xylose resulted in higher yields (0.60 g g-1) than use of xylose alone. Fermenting glucose mixed with fructose gave a lower yield (0.58 g g-1) than fructose used as the sole carbon source. The reason is an increased pyruvate production. The pyruvate concentration decreased later in the fermentation. Final succinic acid concentrations were in the range of 25-40 g L-1. Acetic and pyruvic acid were the only other products detected and accumulated to concentrations of 2.7-6.7 and 0-2.7 g L-1. Production of succinic acid decreased when organic acid concentrations reached approximately 30 g L-1. This study demonstrates that E. coli strain AFP184 is able to produce succinic acid in a low cost medium from a variety of sugars with only small amounts of byproducts formed.

  • 4.
    Bansal, Namita
    et al.
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Bhalla, Aditya
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Pattathil, Sivakumar
    University of Georgia, Complex Carbohydrate Research Center, University of Georgia, Athens, GA.
    Adelman, Sara L.
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Hahn, Michael G
    University of Georgia, Complex Carbohydrate Research Center, University of Georgia, Athens, GA.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Hegg, Eric L.
    Michigan State University, DOE-Great Lakes Bioenergy Research Center, University of Wisconsin, Madison.
    Cell wall-associated transition metals improve alkaline-oxidative pretreatment in diverse hardwoods2016In: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270, Vol. 18, no 5, p. 1405-1415Article in journal (Refereed)
    Abstract [en]

    The responses of four diverse hardwoods (hybrid poplar, silver birch, hybrid aspen, and sugar maple) to alkaline hydrogen peroxide (AHP) pretreated at ambient temperature and pressure were analyzed to gain a deeper understanding of the cell wall properties that contribute to differences in enzymatic hydrolysis efficacy following alkaline-oxidative pretreatment. The enzymatic hydrolysis yields of these diverse hardwoods increased significantly with increasing the cell wall-associated, redox-active transition metal content. These increases in hydrolysis yields were directly correlated with improved delignification. Furthermore, we demonstrated that these improvements in hydrolysis yields could be achieved either through elevated levels of naturally-occurring metals, namely Cu, Fe, and Mn, or by the addition of a homogeneous transition metal catalyst (e.g. Cu 2,2′-bipyridine complexes) capable of penetrating into the cell wall matrix. Removal of naturally-occurring cell wall-associated transition metals by chelation resulted in substantial decreases in the hydrolysis yields following AHP pretreatment, while re-addition of metals in the form of Cu 2,2′-bipyridine complexes and to a limited extent Fe 2,2′-bipyridine complexes prior to pretreatment restored the improved hydrolysis yields. Glycome profiles showed improved extractability of xylan, xyloglucan, and pectin epitopes with increasing hydrolysis yields for the diverse hardwoods subjected to the alkaline-oxidative pretreatment, demonstrating that the strength of association between cell wall matrix polymers decreased as a consequence of improved delignification

  • 5.
    Berglund, Kris
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Fermentation-Based Building Blocks for Renewable Resource-Based Surfactants2010In: Surfactants from renewable resources, Chichester: John Wiley & Sons Ltd , 2010, p. 127-141Chapter in book (Refereed)
    Abstract [en]

    'new' top-ranked building blocks; Citric acid recovery from fermentation broths and CaCO3 precipitation; Citric, acetic and lactic acid - top three industrial carboxylic acids; Fermentation-based building blocks for renewable resource-based surfactants; Fermentation-based building blocks for surfactants; Filamentous fungi, Aspergillus niger and Candida yeast strains; New fermentation-based building blocks; Organic acid metabolites - as hydrophilic moiety; Sulfonates - largest market share of anionic surfactants; Sulfosuccinate class of surfactants

  • 6.
    Bhalla, Aditya
    et al.
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Bansal, Namita
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Stoklosa, Ryan J.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Fountain, Mackenzie
    Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing.
    Ralph, John P.
    DOE-Great Lakes Bioenergy Research Center, University of Wisconsin, Madison.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Hegg, Eric L.
    Michigan State University, DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Effective alkaline metal-catalyzed oxidative delignification of hybrid poplar2016In: Biotechnology for Biofuels, ISSN 1754-6834, E-ISSN 1754-6834, Vol. 9, article id 34Article in journal (Refereed)
    Abstract [en]

    BackgroundStrategies to improve copper-catalyzed alkaline hydrogen peroxide (Cu-AHP) pretreatment of hybrid poplar were investigated. These improvements included a combination of increasing hydrolysis yields, while simultaneously decreasing process inputs through (i) more efficient utilization of H2O2 and (ii) the addition of an alkaline extraction step prior to the metal-catalyzed AHP pretreatment. We hypothesized that utilizing this improved process could substantially lower the chemical inputs needed during pretreatment.ResultsHybrid poplar was pretreated utilizing a modified process in which an alkaline extraction step was incorporated prior to the Cu-AHP treatment step and H2O2 was added batch-wise over the course of 10 h. Our results revealed that the alkaline pre-extraction step improved both lignin and xylan solubilization, which ultimately led to improved glucose (86 %) and xylose (95 %) yields following enzymatic hydrolysis. An increase in the lignin solubilization was also observed with fed-batch H2O2 addition relative to batch-only addition, which again resulted in increased glucose and xylose yields (77 and 93 % versus 63 and 74 %, respectively). Importantly, combining these strategies led to significantly improved sugar yields (96 % glucose and 94 % xylose) following enzymatic hydrolysis. In addition, we found that we could substantially lower the chemical inputs (enzyme, H2O2, and catalyst), while still maintaining high product yields utilizing the improved Cu-AHP process. This pretreatment also provided a relatively pure lignin stream consisting of ≥90 % Klason lignin and only 3 % xylan and 2 % ash following precipitation. Two-dimensional heteronuclear single-quantum coherence (2D HSQC) NMR and size-exclusion chromatography demonstrated that the solubilized lignin was high molecular weight (Mw ≈ 22,000 Da) and only slightly oxidized relative to lignin from untreated poplar.ConclusionsThis study demonstrated that the fed-batch, two-stage Cu-AHP pretreatment process was effective in pretreating hybrid poplar for its conversion into fermentable sugars. Results showed sugar yields near the theoretical maximum were achieved from enzymatically hydrolyzed hybrid poplar by incorporating an alkaline extraction step prior to pretreatment and by efficiently utilizing H2O2 during the Cu-AHP process. Significantly, this study reports high sugar yields from woody biomass treated with an AHP pretreatment under mild reaction conditions.

  • 7.
    Bhalla, Aditya
    et al.
    Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI, USA. DOE Great Lakes Bioenergy Research Center (GLBRC), Michigan State University, East Lansing, MI, USA.
    Cai, Charles M.
    Department of Chemical and Environmental Engineering, University of California, Riverside, CA, USA. BioEnergy Science Center (BESC) and Center for Bioenergy Innovation (CBI), Oak Ridge National Laboratory, Oak Ridge, TN, USA.
    Xu, Feng
    Joint BioEnergy Institute (JBEI), Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
    Singh, Sandip K.
    Chemical & Biological Engineering Department, Montana State University, Bozeman, MT, USA.
    Bansal, Namita
    Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI, USA DOE Great Lakes Bioenergy Research Center (GLBRC), Michigan State University, East Lansing, MI, USA.
    Phongpreecha, Thanaphong
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI, USA.
    Dutta, Tanmoy
    Joint BioEnergy Institute (JBEI), Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
    Foster, Cliff E.
    DOE Great Lakes Bioenergy Research Center (GLBRC), Michigan State University, East Lansing, MI, USA.
    Kumar, Rajeev
    Department of Chemical and Environmental Engineering, University of California, Riverside, CA, USA BioEnergy Science Center (BESC) and Center for Bioenergy Innovation (CBI), Oak Ridge National Laboratory, Oak Ridge, TN, USA.
    Simmons, Blake A.
    Joint BioEnergy Institute (JBEI), Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
    Singh, Seema
    Joint BioEnergy Institute (JBEI), Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
    Wyman, Charles E.
    Department of Chemical and Environmental Engineering, University of California, Riverside, CA, USA. BioEnergy Science Center (BESC) and Center for Bioenergy Innovation (CBI), Oak Ridge National Laboratory, Oak Ridge, TN, USA.
    Hegg, Eric L.
    Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI, USA DOE Great Lakes Bioenergy Research Center (GLBRC), Michigan State University, East Lansing, MI, USA.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering. DOE Great Lakes Bioenergy Research Center (GLBRC), Michigan State University, East Lansing, MI, USA. Chemical & Biological Engineering Department, Montana State University, Bozeman, MT, USA. Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI, USA.
    Performance of three delignifying pretreatments on hardwoods: hydrolysis yields, comprehensive mass balances, and lignin properties2019In: Biotechnology for Biofuels, ISSN 1754-6834, E-ISSN 1754-6834, Vol. 12, article id 213Article in journal (Refereed)
    Abstract [en]

    Background

    In this work, three pretreatments under investigation at the DOE Bioenergy Research Centers (BRCs) were subjected to a side-by-side comparison to assess their performance on model bioenergy hardwoods (a eucalyptus and a hybrid poplar). These include co-solvent-enhanced lignocellulosic fractionation (CELF), pretreatment with an ionic liquid using potentially biomass-derived components (cholinium lysinate or [Ch][Lys]), and two-stage Cu-catalyzed alkaline hydrogen peroxide pretreatment (Cu-AHP). For each of the feedstocks, the pretreatments were assessed for their impact on lignin and xylan solubilization and enzymatic hydrolysis yields as a function of enzyme loading. Lignins recovered from the pretreatments were characterized for polysaccharide content, molar mass distributions, β-aryl ether content, and response to depolymerization by thioacidolysis.

    Results

    All three pretreatments resulted in significant solubilization of lignin and xylan, with the CELF pretreatment solubilizing the majority of both biopolymer categories. Enzymatic hydrolysis yields were shown to exhibit a strong, positive correlation with the lignin solubilized for the low enzyme loadings. The pretreatment-derived solubles in the [Ch][Lys]-pretreated biomass were presumed to contribute to inhibition of enzymatic hydrolysis in the eucalyptus as a substantial fraction of the pretreatment liquor was carried forward into hydrolysis for this pretreatment. The pretreatment-solubilized lignins exhibited significant differences in polysaccharide content, molar mass distributions, aromatic monomer yield by thioacidolysis, and β-aryl ether content. Key trends include a substantially higher polysaccharide content in the lignins recovered from the [Ch][Lys] pretreatment and high β-aryl ether contents and aromatic monomer yields from the Cu-AHP pretreatment. For all lignins, the 13C NMR-determined β-aryl ether content was shown to be correlated with the monomer yield with a second-order functionality.

    Conclusions

    Overall, it was demonstrated that the three pretreatments highlighted in this study demonstrated uniquely different functionalities in reducing biomass recalcitrance and achieving higher enzymatic hydrolysis yields for the hybrid poplar while yielding a lignin-rich stream that may be suitable for valorization. Furthermore, modification of lignin during pretreatment, particularly cleavage of β-aryl ether bonds, is shown to be detrimental to subsequent depolymerization.

  • 8.
    Crowe, Jacob D.
    et al.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Feringa, Nicholas
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Pattathil, Sivakumar
    Complex Carbohydrate Research Center, University of Georgia, Athens, GA.
    Merritt, Brian B.
    Complex Carbohydrate Research Center, University of Georgia, Athens, GA.
    Foster, Cliff E.
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, MI.
    Dines, Dayna
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, MI.
    Ong, Rebecca G.
    Department of Chemical Engineering, Michigan Technological University, Houghton, MI.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Identification of developmental stage and anatomical fraction contributions to cell wall recalcitrance in switchgrass2017In: Biotechnology for Biofuels, ISSN 1754-6834, E-ISSN 1754-6834, Vol. 10, no 1, article id 184Article in journal (Refereed)
    Abstract [en]

    Background: Heterogeneity within herbaceous biomass can present important challenges for processing feedstocks to cellulosic biofuels. Alterations to cell wall composition and organization during plant growth represent major contributions to heterogeneity within a single species or cultivar. To address this challenge, the focus of this study was to characterize the relationship between composition and properties of the plant cell wall and cell wall response to deconstruction by NaOH pretreatment and enzymatic hydrolysis for anatomical fractions (stem internodes, leaf sheaths, and leaf blades) within switchgrass at various tissue maturities as assessed by differing internode. Results: Substantial differences in both cell wall composition and response to deconstruction were observed as a function of anatomical fraction and tissue maturity. Notably, lignin content increased with tissue maturity concurrently with decreasing ferulate content across all three anatomical fractions. Stem internodes exhibited the highest lignin content as well as the lowest hydrolysis yields, which were inversely correlated to lignin content. Confocal microscopy was used to demonstrate that removal of cell wall aromatics (i.e., lignins and hydroxycinnamates) by NaOH pretreatment was non-uniform across diverse cell types. Non-cellulosic polysaccharides were linked to differences in cell wall response to deconstruction in lower lignin fractions. Specifically, leaf sheath and leaf blade were found to have higher contents of substituted glucuronoarabinoxylans and pectic polysaccharides. Glycome profiling demonstrated that xylan and pectic polysaccharide extractability varied with stem internode maturity, with more mature internodes requiring harsher chemical extractions to remove comparable glycan abundances relative to less mature internodes. While enzymatic hydrolysis was performed on extractives-free biomass, extractible sugars (i.e., starch and sucrose) comprised a significant portion of total dry weight particularly in stem internodes, and may provide an opportunity for recovery during processing. Conclusions: Cell wall structural differences within a single plant can play a significant role in feedstock properties and have the potential to be exploited for improving biomass processability during a biorefining process. The results from this work demonstrate that cell wall lignin content, while generally exhibiting a negative correlation with enzymatic hydrolysis yields, is not the sole contributor to cell wall recalcitrance across diverse anatomical fractions within switchgrass

  • 9.
    Crowe, Jacob D.
    et al.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Zarger, Rachael A.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Department of Chemical Engineering and Materials Science, Michigan State University; DOE-Great Lakes Bioenergy Research Center, and Department of Biosystems & Agricultural Engineering, Michigan State University.
    Relating nanoscale accessibility within plant cell walls to improved enzyme hydrolysis yields in corn stover subjected to diverse pretreatments2017In: Journal of Agricultural and Food Chemistry, ISSN 0021-8561, E-ISSN 1520-5118, Vol. 65, no 39, p. 8652-8662Article in journal (Refereed)
    Abstract [en]

    Simultaneous chemical modification and physical reorganization of plant cell walls via alkaline hydrogen peroxide or liquid hot water pretreatment can alter cell wall structural properties impacting nanoscale porosity. Nanoscale porosity was characterized using solute exclusion to assess accessible pore volumes, water retention value as a proxy for accessible water-cell walls surface area, and solute-induced cell wall swelling to measure cell wall rigidity. Key findings concluded that delignification by alkaline hydrogen peroxide pretreatment decreased cell wall rigidity and that the subsequent cell wall swelling resulted increased nanoscale porosity and improved enzyme binding and hydrolysis compared to limited swelling and increased accessible surface areas observed in liquid hot water pretreated biomass. The volume accessible to a 90 Å dextran probe within the cell wall was found to be correlated to both enzyme binding and glucose hydrolysis yields, indicating cell wall porosity is a key contributor to effective hydrolysis yields.

  • 10.
    Enman, Josefine
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Hodge, David
    Berglund, Kris
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Growth promotive conditions for enhanced eritadenine production during submerged cultivation of Lentinus edodes2012In: Journal of chemical technology and biotechnology (1986), ISSN 0268-2575, E-ISSN 1097-4660, Vol. 87, no 7, p. 903-907Article in journal (Refereed)
    Abstract [en]

    Background: Mycelium of the medicinal mushroom shiitake, Lentinus edodes, is a potential source for production of the blood cholesterol reducing compound eritadenine. To increase the mycelial biomass and in turn the production of eritadenine, a potential growth promoting substance in the form of a water extract of distillers dried grains with solubles (DDGS) was added to the culture media. Results: The hot water extract of DDGS was shown to considerably increase the growth of shiitake mycelia in bioreactor cultivations; the mycelial yield was 2-3 times higher than in the control, and the highest final biomass concentration obtained was 3.4 g L -1. Further, by using shake flask cultures as inoculums the bioreactor cultivation time could be reduced by 1 week for some of the experiments. The highest final titer of eritadenine in the present study was 25.1 mg L -1, which was about 2 times higher than in the control, and was also obtained when a water extract of DDGS was added to the culture medium. Conclusion: It was demonstrated that a water extract of DDGS promoted the growth of shiitake mycelia in bioreactor cultivations, along with enhanced eritadenine production

  • 11.
    Enman, Josefine
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hodge, David
    Berglund, Kris
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Rova, Ulrika
    Production of the bioactive compound eritadenine by submerged cultivation of shiitake (Lentinus edodes) mycelia2008In: Journal of Agricultural and Food Chemistry, ISSN 0021-8561, E-ISSN 1520-5118, Vol. 56, no 8, p. 2609-2612Article in journal (Refereed)
    Abstract [en]

    Fruit bodies and mycelia of shiitake mushroom (Lentinus edodes) have been shown to contain the cholesterol-reducing compound eritadenine, 2(R),3(R)-dihydroxy-4-(9-adenyl)butyric acid. In the search for a production method for eritadenine, shiitake mycelia were investigated in the present study. The mycelia were cultivated both in shake flasks and in bioreactors, to investigate the effects of pH, stirring rate, and reactor type on the production and distribution of eritadenine. Both the biomass and the culture broth were examined for their eritadenine content. In the shake flasks, the final concentration of eritadenine was 1.76 mg/L and eritadenine was equally distributed between the mycelia and the growth media. In the bioreactors, the shiitake mycelia were found to contain eritadenine in relatively low levels, whereas the majority, 90.6-98.9%, was detected in the growth media. Applying a stirring rate of 250 rpm during bioreactor cultivation resulted in the highest eritadenine concentrations: 10.23 mg/L when the pH was uncontrolled and 9.59 mg/L when the pH was controlled at 5.7. Reducing the stirring rate to 50 rpm resulted in a decreased eritadenine concentration, both at pH 5.7 (5.25 mg/L) and when pH was not controlled (5.50 mg/L). The mycelia in the shake flask cultures appeared as macroscopic aggregates, whereas mycelia cultivated in bioreactors grew more as freely dispersed filaments. This study demonstrates for the first time the extra- and intracellular distribution of eritadenine produced by shiitake mycelial culture and the influence of reactor conditions on the mycelial morphology and eritadenine concentrations.

  • 12.
    Gowtham, Yogender Kumar
    et al.
    Clemson University.
    Miller, Kristen P.
    Clemson University.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Henson, J. Michael
    Clemson University.
    Harcum, Sarah W.
    Clemson University.
    Novel two-stage fermentation process for bioethanol production using Saccharomyces pastorianus2014In: Biotechnology progress (Print), ISSN 8756-7938, E-ISSN 1520-6033, Vol. 30, no 2, p. 300-310Article in journal (Refereed)
    Abstract [en]

    Bioethanol produced from lignocellulosic materials has the potential to be economically feasible, if both glucose and xylose released from cellulose and hemicellulose can be efficiently converted to ethanol. Saccharomyces spp. can efficiently convert glucose to ethanol; however, xylose conversion to ethanol is a major hurdle due to lack of xylose-metabolizing pathways. In this study, a novel two-stage fermentation process was investigated to improve bioethanol productivity. In this process, xylose is converted into biomass via non-Saccharomyces microorganism and coupled to a glucose-utilizing Saccharomyces fermentation. Escherichia coli was determined to efficiently convert xylose to biomass, which was then killed to produce E. coli extract. Since earlier studies with Saccharomyces pastorianus demonstrated that xylose isomerase increased ethanol productivities on pure sugars, the addition of both E. coli extract and xylose isomerase to S. pastorianus fermentations on pure sugars and corn stover hydrolysates were investigated. It was determined that the xylose isomerase addition increased ethanol productivities on pure sugars but was not as effective alone on the corn stover hydrolysates. It was observed that the E. coli extract addition increased ethanol productivities on both corn stover hydrolysates and pure sugars. The ethanol productivities observed on the corn stover hydrolysates with the E. coli extract addition was the same as observed on pure sugars with both E. coli extract and xylose isomerase additions. These results indicate that the two-stage fermentation process has the capability to be a competitive alternative to recombinant Saccharomyces cerevisiae-based fermentations.

  • 13. Helmerius, Jonas
    et al.
    Walter, Jonas Vinblad von
    Smurfit Kappa Kraftliner AB.
    Rova, Ulrika
    Berglund, Kris
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Hodge, David
    Production of value added chemicals from xylan extraction in a Kraft pulp mill and the effect on pulp quality2008Conference paper (Other academic)
    Abstract [en]

    In the Kraft process hemicelluloses are lost in the cooking procedure to the black liquor stream, which is subsequently burnt in the recovery boiler to recover cooking chemicals and to produce steam and energy. Hemicelluloses have a low heating value compared to lignin and therefore recovery of hemicelluloses at an earlier stage of the Kraft process followed by biochemical conversionintohighvalue-conversion intohighvalue-into high value-added products might offer a muchbettereconomicopportunity.much better economic opportunityIn collaboration with the research and development department of Smurfit Kappa Kraftliner AB, Piteå, Sweden, alkali and water extractions of birch wood were performed under conditions compatible with the Kraft process, at different times, temperatures and alkali charges. The extraction conditions were set in a range suitable with the current pulp process at Smurfit Kappa Kraftliner. TherequirementsforprocessThe requirements for process configurations, based on either hot water or alkali extraction were also explored. ThexylanyieldsfromdifferentextractiontrialswereThe xylan yields from different extraction trials were measured and the chips from those extraction trials were cooked, refined and turned into sheets of paper. The effects on paper quality were compared with a reference pulp made from the same wooden chips. Recovered xylans from water extracted birch wood chips were subjected to secondary hydrolysis, enzymatic or sulphuricacid.sulphuric acidDetoxification of the hydrolysate with active carbon and regulation of pH were performed before fermentation. FermentationofthexyloseFermentation of the xylose hydrolysate to succinic acid was demonstrated by the use of thethe succinic acid producer Escherichia coli AFP184.

  • 14. Helmerius, Jonas
    et al.
    Walter, Jonas Vinblad von
    Smurfit Kappa Kraftliner AB.
    Rova, Ulrika
    Berglund, Kris
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Hodge, David
    Production of value added chemicals from xylan extraction in a Kraft pulp mill and the effect on pulp quality2008Conference paper (Other academic)
    Abstract [en]

    In the Kraft process hemicelluloses are lost in the cooking procedure to the black liquor stream, which is subsequently burnt in the recovery boiler to recover cooking chemicals and to produce steam and energy. Hemicelluloses have a low heating value compared to lignin and therefore recovery of hemicelluloses at an earlier stage of the Kraft process followed by biochemical conversion into high value-added products might offer a much better economic opportunity. In collaboration with the research and development department of Smurfit Kappa Kraftliner AB, Piteå, Sweden, alkali and water extractions of birch wood were performed under conditions compatible with the Kraft process, at different times, temperatures and alkali charges. The extraction conditions were set in a range suitable with the current pulp process at Smurfit Kappa Kraftliner. The requirements for process configurations, based on either hot water or alkali extraction were also explored. The xylan yields from different extraction trials were measured and the chips from those extraction trials were cooked, refined and turned into sheets of paper. The effects on paper quality were compared with a reference pulp made from the same wooden chips. Recovered xylans from water extracted birch wood chips were subjected to secondary hydrolysis, enzymatic or sulphuric acid. Detoxification of the hydrolysate with active carbon and regulation of pH were performed before fermentation. Fermentation of the xylose hydrolysate to succinic acid was demonstrated by the use of the succinic acid producer Escherichia coli AFP184.

  • 15.
    Helmerius, Jonas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Walter, Jonas Vinblad von
    Luleå tekniska universitet.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Berglund, Kris
    Hodge, David B.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Impact of hemicellulose pre-extraction for bioconversion on birch Kraft pulp properties2010In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 101, no 15, p. 5996-6005Article in journal (Refereed)
    Abstract [en]

    The combination of hemicellulose extraction with chemical pulping processes is one approach to generate a sugar feedstock amenable to biochemical transformation to fuels and chemicals. Extractions of hemicellulose from silver birch (Betula pendula) wood chips using either water or Kraft white liquor (NaOH, Na2S, and Na2CO3) were performed under conditions compatible with Kraft pulping, using times ranging between 20 and 90 min, temperatures of 130-160 °C, and effective alkali (EA) charges of 0-7%. The chips from select extractions were subjected to subsequent Kraft pulping and the refined pulps were made into handsheets. Several metrics for handsheet strength properties were compared with a reference pulp made without an extraction step. This study demonstrated that white liquor can be utilized to extract xylan from birch wood chips prior to Kraft cooking without decreasing the pulp yield and paper strength properties, while simultaneously impregnating cooking alkali into the wood chips. However, for the alkaline conditions tested extractions above pH 10 resulted in low concentrations of xylan. Water extractions resulted in the highest final concentrations of xylan; yielding a liquor without the presence of toxic or inhibitory inorganics and minimal soluble aromatics that we demonstrate can be successfully enzymatically hydrolyzed to monomeric xylose and fermented to succinic acid. However, water extractions were found to negatively impact some pulp properties including decreases in compression strength, bursting strength, tensile strength, and tensile stiffness while exhibiting minimal impact on elongation and slight improvement in tearing strength index.

  • 16. Hodge, David
    et al.
    Andersson, Christian
    Berglund, Kris
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Rova, Ulrika
    Detoxification requirements for bioconversion of softwood dilute acid hydrolyzates to succinic acid2009In: Enzyme and microbial technology, ISSN 0141-0229, E-ISSN 1879-0909, Vol. 44, no 5, p. 309-316Article in journal (Refereed)
    Abstract [en]

    In this work an Escherichia coli metabolically engineered to ferment lignocellulosic biomass sugars to succinic acid was tested for growth and fermentation of detoxified softwood dilute sulfuric acid hydrolyzates, and the minimum detoxification requirements were investigated with activated carbon and/or overliming treatments. Detoxified hydrolyzates supported fast growth and complete fermentation of all hydrolyzate sugars to succinate at yields comparable to pure sugar, while untreated hydrolyzates were unable to support either growth or fermentation. Activated carbon treatment was able to remove significantly more HMF and phenolics than overliming. However, in some cases, overliming treatment was capable of generating a fermentable hydrolyzate where activated carbon treatment was not. The implications of this are that in addition to the known organic inhibitors, the changes in the inorganic content and/or composition due to overliming are significant to the hydrolyzate toxicity. It was also found that any HMF remaining after detoxification was completely metabolized during aerobic cell growth on the hydrolyzates that were capable of supporting growth.

  • 17. Hodge, David
    et al.
    Andersson, Christian
    Helmerius, Jonas
    Walter, J. Vinblad von
    Rova, Ulrika
    Berglund, Kris
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Succinic acid production from forest based raw materials2008Conference paper (Other academic)
    Abstract [en]

    Lignocellulosic biomass and particularly hemicellulose from the forest products industry represents a large reservoir of sugars with the potential to be converted to higher value products through bioprocessing. This presentation will cover several projects regarding the fractionation and conversion of lignocellulose to succinic acid, a potentially important platform molecule in the synthesis of a number of commodity and specialty chemicals. The first of these investigates the feasibility of integrating a hardwood hemicellulose sugar extraction step into a Kraft pulping process with the intention of utilizing the hemicellulose as a fermentation feedstock. The requirements on processing configurations for hemicellulose extraction and recovery are compared, and a number of experimental parameters affecting the extraction (alkali, temperature, time) are investigated. Pulp quality is an important property and hemicellulose extraction can result in negatively affect the strength of the paper, which is also investigated. The second portion of the work deals with the fermentation requirements for microbial conversion of dilute acid hydrolyzed softwood to succinic acid. In particular, activated carbon and overliming detoxifications were tested for the ability to remove fermentation inhibitors and improve the fermentability of the hydrolyzates.

  • 18.
    Hodge, David
    et al.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Helmerius, Jonas
    Walter, Jonas Vinblad von
    Sun Pine Biodiesel AB, Piteå.
    Lindström, Curt
    Smurfit Kappa Kraftliner AB, Piteå.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Impact of hemicellulose pre-extraction for bioconversion on birch kraft pulp properties2009Conference paper (Other academic)
    Abstract [en]

    The carbohydrate portion of lignocellulosic feedstocks are ideally suited to conversion via biochemical transformations because of their crucial role in cellular metabolism. The combination of hemicelluloses extraction with pulping processes could be one way to generate a sugar feedstock amenable to biochemical transformation to fuels and chemical intermediates. White liquor, green liquor, and water HC extractions of birch wood were performed under conditions compatible with the Kraft process, at different times, temperatures and alkali charges. The effective alkali charge was in extractions between 0%-7% and temperature between 130°C-160°C for 20-90 minutes. The xylan yields from different HC extractions were measured and the chips from select HC extractions were cooked, and the refined pulps were made into hand sheets. Several metrics for hand sheet quality were compared with a reference pulp made from the same wood chips. It is possible using white liquor to extract xylan from birch wood chips prior Kraft cooking without decreasing the pulp yield and paper strength properties, and at the same time achieve an impregnation of the wood chips. It is not possible in that extraction to attain extracted and hydrolyzed liquor containing a fermentable concentration of xylose, 2.63 g/L in this study. Increased extracted wood material, increased final acetic acid concentration and decreased final xylan concentration together with increased effective alkali charge at the same extraction temperature and time in white liquor extractions performed support that xylan degradation increases. Using white liquor or green liquor under the conditions investigated degrades xylan resulting in significant losses of xylose that could have been used as substrate in fermentation processes.

  • 19.
    Hodge, David
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Karim, M. Nazmul
    Texas Tech University, Department of Chemical Engineering.
    Schell, Daniel J.
    National Renewable Energy Laboratory, National Bioenergy Center.
    McMillan, James D.
    National Renewable Energy Laboratory, National Bioenergy Center.
    Model-based fed-batch for high-solids enzymatic cellulose hydrolysis2009In: Applied Biochemistry and Biotechnology, ISSN 0273-2289, E-ISSN 1559-0291, Vol. 152, no 1, p. 88-107Article in journal (Refereed)
    Abstract [en]

    While many kinetic models have been developed for the enzymatic hydrolysis of cellulose, few have been extensively applied for process design, optimization, or control. High-solids operation of the enzymatic hydrolysis of lignocellulose is motivated by both its operation decreasing capital costs and increasing product concentration and hence separation costs. This work utilizes both insights obtained from experimental work and kinetic modeling to develop an optimization strategy for cellulose saccharification at insoluble solids levels greater than 15% (w/w), where mixing in stirred tank reactors (STRs) becomes problematic. A previously developed model for batch enzymatic hydrolysis of cellulose was modified to consider the effects of feeding in the context of fed-batch operation. By solving the set of model differential equations, a feeding profile was developed to maintain the insoluble solids concentration at a constant or manageable level throughout the course of the reaction. Using this approach, a stream of relatively concentrated solids (and cellulase enzymes) can be used to increase the final sugar concentration within the reactor without requiring the high initial levels of insoluble solids that would be required if the operation were performed in batch mode. Experimental application in bench-scale STRs using a feed stream of dilute acid-pretreated corn stover solids and cellulase enzymes resulted in similar cellulose conversion profiles to those achieved in batch shake-flask reactors where temperature control issues are mitigated. Final cellulose conversions reached approximately 80% of theoretical for fed-batch STRs fed to reach a cumulative solids level of 25% (w/w) initial insoluble solids

  • 20. Hodge, David
    et al.
    Karim, M.N.
    Texas Tech University, Lubbock.
    Schell, D.J.
    National Bioenergy Center, National Renewable Energy Laboratory, Golden, CO.
    McMillan, J.D.
    National Bioenergy Center, National Renewable Energy Laboratory, Golden, CO.
    Soluble and insoluble solids contributions to high-solids enzymatic hydrolysis of lignocellulose2008In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 99, no 18, p. 8940-8948Article in journal (Refereed)
    Abstract [en]

    The rates and extents of enzymatic cellulose hydrolysis of dilute acid pretreated corn stover (PCS) decline with increasing slurry concentration. However, mass transfer limitations are not apparent until insoluble solids concentrations approach 20% w/w, indicating that inhibition of enzyme hydrolysis at lower solids concentrations is primarily due to soluble components. Consequently, the inhibitory effects of pH-adjusted pretreatment liquor on the enzymatic hydrolysis of PCS were investigated. A response surface methodology (RSM) was applied to empirically model how hydrolysis performance varied as a function of enzyme loading (12-40 mg protein/g cellulose) and insoluble solids concentration (5-13%) in full-slurry hydrolyzates. Factorial design and analysis of variance (ANOVA) were also used to assess the contribution of the major classes of soluble components (acetic acid, phenolics, furans, sugars) to total inhibition. High sugar concentrations (130 g/L total initial background sugars) were shown to be the primary cause of performance inhibition, with acetic acid (15 g/L) only slightly inhibiting enzymatic hydrolysis and phenolic compounds (9 g/L total including vanillin, syringaldehyde, and 4-hydroxycinnamic acid) and furans (8 g/L total of furfural and hydroxymethylfurfural, HMF) with only a minor effect on reaction kinetics. It was also demonstrated that this enzyme inhibition in high-solids PCS slurries can be approximated using a synthetic hydrolyzate composed of pure sugars supplemented with a mixture of acetic acid, furans, and phenolic compounds, which indicates that generally all of the reaction rate-determining soluble compounds for this system can be approximated synthetically.

  • 21.
    Hodge, David
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Stoklosa, Ryan J.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Extraction, recovery, and characterization of hardwood and grass hemicelluloses for integration into biorefining processes2012In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 51, no 34, p. 11045-11053Article in journal (Refereed)
    Abstract [en]

    For this work, four hardwoods (silver birch, sugar maple, a hybrid poplar, and a hybrid aspen) and one cultivar of switchgrass were treated with increasing levels of NaOH. The recovered cell wall biopolymers were characterized based on total extraction, precipitation using ethanol or acidification, xylan content, and molar mass of the recovered precipitates. The extractability of cell wall polymers was clearly shown to be a function of the biomass type with more than 50% of the cell walls of switchgrass solubilized by alkali while only up to 20% of the maple was solubilized under comparable conditions. Precipitation with ethanol resulted in high recovery yields of hemicelluloses from the original biomass for silver birch and switchgrass, and most notably, the birch precipitates contained double the hemicellulose content of the precipitates from other feedstock alkali extracts (80% versus 30-50%). The molar masses of the recovered hemicellulosic polysaccharides were characterized using size exclusion chromatography (SEC) and an assay to quantify polysaccharide reducing ends. SEC analysis showed that the biopolymers exhibited a strong tendency to self-associate during elution and that this aggregation could be eliminated through sonication. The reducing end method showed an increase in the number-average degree of polymerization toward an asymptotic maximum with increasing extraction pH, and this value was significantly increased by bleaching the precipitate to remove interference by nonpolysaccharides

  • 22.
    Häggström, Caroline
    et al.
    Wibax AB.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Brandberg, Tomas
    SEKAB E-Technology, School of Engineering, University of Borås.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Integration of Ethanol Fermentation with Second Generation Biofuels Technologies2014In: Biorefineries: Integrated Biochemical Processes for Liquid Biofuels, Amsterdam: Elsevier, 2014, p. 161-187Chapter in book (Refereed)
    Abstract [en]

    This chapter presents an overview of the challenges associated with integrating yeast fermentation into cellulosic biofuel processes, as well as the approaches that might overcome these challenges. The chapter first introduces the design considerations for first-generation ethanol fermentation processes using sugar cane and corn as feedstocks, with an emphasis on process constraints and operation strategies. The chapter then explores methods for improving yield, titer, productivity, and economics. These processing methods illustrate the challenges posed by the fermentation of ethanol from lignocellulose hydrolyzates, especially the differences in process constraints for high-productivity, high-product titer operations. Finally, the chapter discusses an example of aerobic seed cultivation of yeast using a hydrolyzate of dilute acid-hydrolyzed softwood hemicellulose

  • 23. Häggström, Caroline
    et al.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Brandberg, Tomas
    SEKAB E-Technology.
    Hodge, David
    Chemical Engineering & Materials Science, Michigan State University, East Lansing, MI.
    Media requirements for aerobic cultivation of saccharomyces cerevisiae TMB 3400-F30-3 on undetoxified softwood dilute acid hydrolyzate2009Conference paper (Other academic)
    Abstract [en]

    The purpose of this study was to develop a low-cost industrial nutrient medium for the aerobic cultivation of a hydrolyzate-adapted Saccharomyces cerevisiae TMB3400-FT30-3 for subsequent fermentation of dilute acid hydrolyzed softwood. This xylose-utilizing yeast is a promising ethanologen for converting lignocellulosic biomass sugars to ethanol. The dilute acid pretreated softwood hydrolyzate used in the process is a readily available and economic option for a carbon source for cell growth in the fermentation seed tank and has the added advantage of contributing to cell adaptation before the fermentation. The focus of the work was to determine the minimal level of externally-supplied media supplementation in the form of beet molasses and nitrogen in the form of ammonium sulfate that will still result in near-maximal biomass yields during fed-batch aerobic growth. The experimental work showed that it is possible to supply only 10 % of the sugars in the form of beet molasses (or 6.7 g/L of concentrated molasses ) without any significant reduction of the biomass yield from its near maximum value of 0.45 g biomass / g sugar. It was not until the molasses addition was below 9 % that a statistically significant reduction in yield was observed. Reducing the nitrogen from 0.12 to 0.06 g N / g biomass resulted in a statistically significant decrease of the yield.

  • 24.
    Kudahettige-Nilsson, Rasika
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Helmerius, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Nilsson, Robert
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Sjöblom, Magnus
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hodge, David
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Biobutanol Production by Clostridium acetobutylicum Using Xylose Recovered from Birch Kraft Black Liquor2015In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 176, p. 71-79Article in journal (Refereed)
    Abstract [en]

    Acetone-Butanol-Ethanol (ABE) fermentation was studied using acid-hydrolyzed xylan recovered from hardwood Kraft black liquor by CO2 acidification as the only carbon source. Detoxification of hydrolyzate using activated carbon was conducted to evaluate the impact of inhibitor removal and fermentation. Xylose hydrolysis yields as high as 18.4% were demonstrated at the highest severity hydrolysis condition. Detoxification using active carbon was effective for removal of both phenolics (76-81%) and HMF (38-52%). Batch fermentation of the hydrolyzate and semi-defined P2 media resulted in a total solvent yield of 0.12-0.13 g/g and 0.34 g/g, corresponding to a butanol concentration of 1.8-2.1 g/L and 7.3 g/L respectively. This work is the first study of a process for the production of a biologically-derived biofuel from hemicelluloses solubilized during Kraft pulping and demonstrates the feasibility of utilizing xylan recovered directly from industrial Kraft pulping liquors as a feedstock for biological production of biofuels such as butanol.

  • 25.
    Li, Muyang
    et al.
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, Michigan State University, Department of Biosystems & Agricultural Engineering, Michigan State University, East Lansing.
    Heckwolf, Marlies
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Crowe, Jacob D.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Williams, Daniel L.
    Michigan State University, DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Magee, Timothy D.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Kaeppler, Shawn M.
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Lion, Natalia de
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Cell-wall properties contributing to improved deconstruction by alkaline pre-treatment and enzymatic hydrolysis in diverse maize (Zea mays L.) lines2015In: Journal of Experimental Botany, ISSN 0022-0957, E-ISSN 1460-2431, Vol. 66, no 14, p. 4305-4315Article in journal (Refereed)
    Abstract [en]

    A maize (Zea mays L. subsp. mays) diversity panel consisting of 26 maize lines exhibiting a wide range of cell-wall properties and responses to hydrolysis by cellulolytic enzymes was employed to investigate the relationship between cell-wall properties, cell-wall responses to mild NaOH pre-treatment, and enzymatic hydrolysis yields. Enzymatic hydrolysis of the cellulose in the untreated maize was found to be positively correlated with the water retention value, which is a measure of cell-wall susceptibility to swelling. It was also positively correlated with the lignin syringyl/guaiacyl ratio and negatively correlated with the initial cell-wall lignin, xylan, acetate, and p-coumaric acid (pCA) content, as well as pCA released from the cell wall by pre-treatment. The hydrolysis yield following pre-treatment exhibited statistically significant negative correlations to the lignin content after pre-treatment and positive correlations to the solubilized ferulic acid and pCA. Several unanticipated results were observed, including a positive correlation between initial lignin and acetate content, lack of correlation between acetate content and initial xylan content, and negative correlation between each of these three variables to the hydrolysis yields for untreated maize. Another surprising result was that pCA release was negatively correlated with hydrolysis yields for untreated maize and, along with ferulic acid release, was positively correlated with the pre-treated maize hydrolysis yields. This indicates that these properties that may negatively contribute to the recalcitrance in untreated cell walls may positively contribute to their deconstruction by alkaline pre-treatment.

  • 26.
    Li, Muyang
    et al.
    Michigan State University.
    Pattathil, Sivakumar
    University of Georgia.
    Hahn, Michael G
    University of Georgia.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Identification of features associated with plant cell wall recalcitrance to pretreatment by alkaline hydrogen peroxide in diverse bioenergy feedstocks using glycome profiling2014In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, no 33, p. 17282-17292Article in journal (Refereed)
    Abstract [en]

    A woody dicot (hybrid poplar), an herbaceous dicot (goldenrod), and a graminaceous monocot (corn stover) were subjected to alkaline hydrogen peroxide (AHP) pretreatment and subsequent enzymatic hydrolysis in order to assess how taxonomically and structurally diverse biomass feedstocks respond to a mild alkaline oxidative pretreatment and how differing features of the cell wall matrix contribute to its recalcitrance. Using glycome profiling, we determined changes in the extractability of non-cellulosic glucans following pretreatment by screening extracts of the pretreated walls with a panel of 155 cell wall glycan-directed monoclonal antibodies to determine differences in the abundance and distribution of non-cellulosic glycan epitopes in these extracts and assess pretreatment-induced changes in the structural integrity of the cell wall. Two taxonomically-dependent outcomes of pretreatment were identified that both improved the subsequent enzymatic hydrolysis yields but differed in their impacts on cell wall structural integrity. Specifically, it was revealed that goldenrod walls exhibited decreases in all classes of alkali-extractable glycans indicating their solubilization during pretreatment, which was accompanied by an improvement in the subsequent extractability of the remaining cell wall glycans. The corn stover walls did not show the same decreases in glycan abundance in extracts following pretreatment, but rather mild increases in all classes of cell wall glycans, indicating overall weaker associations between cell wall polymers and improved extractability. The hybrid poplar walls were relatively unaffected by pretreatment in terms of composition, enzymatic hydrolysis, and the extractability of cell wall glycans due presumably to their higher lignin content and denser vascular structure.

  • 27.
    Li, Muyang
    et al.
    Department of Plant Biology, Michigan State University, East Lansing, .
    Williams, Daniel L.
    DOE Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, .
    Heckwolf, Marlies
    Department of Agronomy, University of Wisconsin, Madison.
    de Leon, Natalia
    Department of Agronomy, University of Wisconsin, Madison.
    Kaeppler, Shawn
    Department of Agronomy, University of Wisconsin, Madison.
    Sykes, Robert W.
    National Renewable Energy Laboratory, Golden.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Prediction of Cell Wall Properties and Response to Deconstruction Using Alkaline Pretreatment in Diverse Maize Genotypes Using Py-MBMS and NIR2017In: Bioenergy Research, ISSN 1939-1234, E-ISSN 1939-1242, Vol. 10, no 2, p. 329-343Article in journal (Refereed)
    Abstract [en]

    In this work, we explore the ability of several characterization approaches for phenotyping to extract information about plant cell wall properties in diverse maize genotypes with the goal of identifying approaches that could be used to predict the plant’s response to deconstruction in a biomass-to-biofuel process. Specifically, a maize diversity panel was subjected to two high-throughput biomass characterization approaches, pyrolysis molecular beam mass spectrometry (py-MBMS) and near-infrared (NIR) spectroscopy, and chemometric models to predict a number of plant cell wall properties as well as enzymatic hydrolysis yields of glucose following either no pretreatment or with mild alkaline pretreatment. These were compared to multiple linear regression (MLR) models developed from quantified properties. We were able to demonstrate that direct correlations to specific mass spectrometry ions from pyrolysis as well as characteristic regions of the second derivative of the NIR spectrum regions were comparable in their predictive capability to partial least squares (PLS) models for p-coumarate content, while the direct correlation to the spectral data was superior to the PLS for Klason lignin content and guaiacyl monomer release by thioacidolysis as assessed by cross-validation. The PLS models for prediction of hydrolysis yields using either py-MBMS or NIR spectra were superior to MLR models based on quantified properties for unpretreated biomass. However, the PLS models using the two high-throughput characterization approaches could not predict hydrolysis following alkaline pretreatment while MLR models based on quantified properties could. This is likely a consequence of quantified properties including some assessments of pretreated biomass, while the py-MBMS and NIR only utilized untreated biomass.

  • 28.
    Li, Muyang
    et al.
    Department of Biosystems & Agricultural Engineering, Michigan State University, East Lansing .
    Yan, Guilong
    School of Life Science, Huaiyin Normal University, Huaian, Jiangsu.
    Bhalla, Aditya
    DOE Great Lakes Bioenergy Research Center, Michigan State University.
    Maldonado-Pereira, Lisaura
    Department of Biosystems & Agricultural Engineering, Michigan State University, East Lansing .
    Russell, Petria R.
    Department of Chemical & Biological Engineering, Montana State University.
    Ding, Shi-You
    DOE Great Lakes Bioenergy Research Center, Michigan State University.
    Mullet, John E.
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Department of Chemical & Biological Engineering, Montana State University, Bozeman, MT.
    Physical fractionation of sweet sorghum and forage/energy sorghum for optimal processing in a biorefinery2018In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 124, p. 607-616Article in journal (Refereed)
    Abstract [en]

    Sorghum offers enormous potential as a feedstock for the production of fuels and chemicals from both water-extractable sugars and the cell wall biopolymers, while its within-plant structural and compositional heterogeneity may allow for physical fractionations to tailor feedstock properties to a biorefining process. In this study, the stem internodes of two sorghum (Sorghum bicolor L. Moench) genotypes, a sweet sorghum (‘Della’) and a forage/energy sorghum (‘TX08001’), were first subjected to fractionation by manual classification by stem anatomy and internode proximity to the ground to yield 18 fractions. These fractions exhibited substantial differences in cell wall morphology, composition, and recalcitrance to mild alkaline pretreatment and enzymatic hydrolysis. While the sweet sorghum cultivar held nearly 70% more water-extractable sugar (sucrose, glucose, fructose, starch) in the stems than the forage/energy sorghum hybrid, both cultivars exhibited comparable diversity of composition and these compositions were remarkably similar in similar tissues and stem regions between the two cultivars. The fractions isolated from the pith parenchyma were the least recalcitrant to mild alkaline pretreatment and enzymatic hydrolysis and contained less lignin than fractions isolated from the epidermis, outer and inner rind, and internal vascular bundles. The pith samples isolated from the lowest region of the stem from both cultivars exhibited near-theoretical sugar hydrolysis yields when no pretreatment was employed and exhibited the lowest lignin contents of any of the fractions. Next, a physical fractionation approach approximating a commercial “de-pithing” process utilizing wet disintegration and sieving was applied to the forage/energy sorghum. A pith-rich fraction representing approximately 20% of the extractives-free mass of the stem could be isolated with this approach and, relative to the other fractions, was low in lignin, high in ash, highly hygroscopic, and showed an improved response to mild alkaline pretreatment and enzymatic hydrolysis at low enzyme loadings. Overall, these results demonstrate how heterogeneity within sorghum stems can be exploited using physical fractionation approaches to yield fractions enriched in desired properties that may allow for more streamlined processing.

  • 29.
    Li, Zhenglun
    et al.
    Michigan State University, Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Bansal, Namita
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Azarpira, Ali
    DOE-Great Lakes Bioenergy Research Center, University of Wisconsin, Madison.
    Bhalla, Aditya
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Chen, Charles H.
    Michigan State University, Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Ralph, John P.
    DOE-Great Lakes Bioenergy Research Center, University of Wisconsin, Madison.
    Hegg, Eric L.
    Michigan State University, DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Chemical and structural changes associated with Cu-catalyzed alkaline-oxidative delignification of hybrid poplar2015In: Biotechnology for Biofuels, ISSN 1754-6834, E-ISSN 1754-6834, Vol. 8, no 1, article id 123Article in journal (Refereed)
    Abstract [en]

    Background: Alkaline hydrogen peroxide pretreatment catalyzed by Cu(II) 2,2′-bipyridine complexes has previously been determined to substantially improve the enzymatic hydrolysis of woody plants including hybrid poplar as a consequence of moderate delignification. In the present work, cell wall morphological and lignin structural changes were characterized for this pretreatment approach to gain insights into pretreatment outcomes and, specifically, to identify the extent and nature of lignin modification. Results: Through TEM imaging, this catalytic oxidation process was shown to disrupt cell wall layers in hybrid poplar. Cu-containing nanoparticles, primarily in the Cu(I) oxidation state, co-localized with the disrupted regions, providing indirect evidence of catalytic activity whereby soluble Cu(II) complexes are reduced and precipitated during pretreatment. The concentration of alkali-soluble polymeric and oligomeric lignin was substantially higher for the Cu-catalyzed oxidative pretreatment. This alkali-soluble lignin content increased with time during the catalytic oxidation process, although the molecular weight distributions were unaltered. Yields of aromatic monomers (including phenolic acids and aldehydes) were found to be less than 0.2 % (wt/wt) on lignin. Oxidation of the benzylic alcohol in the lignin side-chain was evident in NMR spectra of the solubilized lignin, whereas minimal changes were observed for the pretreatment-insoluble lignin. Conclusions: These results provide indirect evidence for catalytic activity within the cell wall. The low yields of lignin-derived aromatic monomers, together with the detailed characterization of the pretreatment-soluble and pretreatment-insoluble lignins, indicate that the majority of both lignin pools remained relatively unmodified. As such, the lignins resulting from this process retain features closely resembling native lignins and may, therefore, be amenable to subsequent valorization.

  • 30.
    Li, Zhenglun
    et al.
    Michigan State University.
    Chen, Charles H.
    Michigan State University.
    Liu, Tongjun
    Michigan State University.
    Mathrubootham, Vaidyanathan
    Michigan State University.
    Hegg, Eric L.
    Michigan State University.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Catalysis with Cuii(bpy) improves alkaline hydrogen peroxide pretreatment2013In: Biotechnology and Bioengineering, ISSN 0006-3592, E-ISSN 1097-0290, Vol. 110, no 4, p. 1078-1086Article in journal (Refereed)
    Abstract [en]

    Copper(II) 2,2′-bipyridine (CuII(bpy))-catalyzed alkaline hydrogen peroxide (AHP) pretreatment was performed on three biomass feedstocks including alkali pre-extracted switchgrass, silver birch, and a hybrid poplar cultivar. This catalytic approach was found to improve the subsequent enzymatic hydrolysis of plant cell wall polysaccharides to monosaccharides for all biomass types at alkaline pH relative to uncatalyzed pretreatment. The hybrid poplar exhibited the most significant improvement in enzymatic hydrolysis with monomeric sugar release and conversions more than doubling from 30% to 61% glucan conversion, while lignin solubilization was increased from 36.6% to 50.2% and hemicellulose solubilization was increased from 14.9% to 32.7%. It was found that CuII(bpy)-catalyzed AHP pretreatment of cellulose resulted in significantly more depolymerization than uncatalyzed AHP pretreatment (78.4% vs. 49.4% decrease in estimated degree of polymerization) and that carboxyl content the cellulose was significantly increased as well (fivefold increase vs. twofold increase). Together, these results indicate that CuII(bpy)-catalyzed AHP pretreatment represents a promising route to biomass deconstruction for bioenergy applications

  • 31.
    Liao, Wei
    et al.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Liu, Yan
    Department of Biosystems & Agricultural Engineering, Michigan State University, East Lansing.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Integrated Farm-Based Biorefinery2014In: Biorefineries: Integrated Biochemical Processes for Liquid Biofuels, Amsterdam: Elsevier, 2014, p. 255-270Chapter in book (Refereed)
    Abstract [en]

    Animal manure and crop residues are agricultural wastes rich in carbohydrates and nitrogen that represent a largely untapped reservoir of biomass. These farm wastes have great potential as feedstocks for the production of renewable biobased energy and chemical products. This chapter presents a novel integrated farm-based biorefining system for producing ethanol, methane, and algal biomass from a mixed feedstock of animal manure and corn stover. The system includes three unit operations for anaerobic digestion (AD), algae cultivation, and bioethanol production. The AD process produces methane and pretreats the biomass fiber for bioethanol production. The algae cultivation process treats the liquid AD effluent, further reducing the environmental impacts of excess nutrients in the agricultural residues and generating a protein-rich algal biomass. Finally, a bioethanol process utilizes the carbohydrates in the AD-treated fiber to produce ethanol. The integrated system uses the advantages of individual biological processes to synergistically improve the energy efficiency of lignocellulosic biofuel production, address the water usage of lignocellulosic biorefining, provide a solution to -problems with feedstock logistics, and alleviate the environmental impacts of agricultural residues. This integrated biological process could eventually lead to reducing our reliance on fossil fuel, while simultaneously maximizing farmers' interests and minimizing environmental impacts

  • 32.
    Liu, Tongjun
    et al.
    Michigan State University.
    Williams, Daniel L.
    Michigan State University.
    Pattathil, Sivakumar
    University of Georgia.
    Li, Muyang
    Michigan State University.
    Hahn, Michael G
    University of Georgia.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Coupling alkaline pre-extraction with alkaline-oxidative post-treatment of corn stover to enhance enzymatic hydrolysis and fermentability2014In: Biotechnology for Biofuels, ISSN 1754-6834, E-ISSN 1754-6834, Vol. 7, article id 48Article in journal (Refereed)
    Abstract [en]

    Background: A two-stage chemical pretreatment of corn stover is investigated comprising an NaOH pre-extraction followed by an alkaline hydrogen peroxide (AHP) post-treatment. We propose that conventional one-stage AHP pretreatment can be improved using alkaline pre-extraction, which requires significantly less H2O2 and NaOH. To better understand the potential of this approach, this study investigates several components of this process including alkaline pre-extraction, alkaline and alkaline-oxidative post-treatment, fermentation, and the composition of alkali extracts.Results: Mild NaOH pre-extraction of corn stover uses less than 0.1 g NaOH per g corn stover at 80 degrees C. The resulting substrates were highly digestible by cellulolytic enzymes at relatively low enzyme loadings and had a strong susceptibility to drying-induced hydrolysis yield losses. Alkaline pre-extraction was highly selective for lignin removal over xylan removal; xylan removal was relatively minimal (similar to 20%). During alkaline pre-extraction, up to 0.10 g of alkali was consumed per g of corn stover. AHP post-treatment at low oxidant loading (25 mg H2O2 per g pre-extracted biomass) increased glucose hydrolysis yields by 5%, which approached near-theoretical yields. ELISA screening of alkali pre-extraction liquors and the AHP post-treatment liquors demonstrated that xyloglucan and beta-glucans likely remained tightly bound in the biomass whereas the majority of the soluble polymeric xylans were glucurono (arabino) xylans and potentially homoxylans. Pectic polysaccharides were depleted in the AHP post-treatment liquor relative to the alkaline pre-extraction liquor. Because the already-low inhibitor content was further decreased in the alkaline pre-extraction, the hydrolysates generated by this two-stage pretreatment were highly fermentable by Saccharomyces cerevisiae strains that were metabolically engineered and evolved for xylose fermentation.Conclusions: This work demonstrates that this two-stage pretreatment process is well suited for converting lignocellulose to fermentable sugars and biofuels, such as ethanol. This approach achieved high enzymatic sugars yields from pretreated corn stover using substantially lower oxidant loadings than have been reported previously in the literature. This pretreatment approach allows for many possible process configurations involving novel alkali recovery approaches and novel uses of alkaline pre-extraction liquors. Further work is required to identify the most economical configuration, including process designs using techno-economic analysis and investigating processing strategies that economize water use.

  • 33.
    Nitsos, Christos
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Stoklosa, Ryan J.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI.
    Karnaouri, Anthi C
    Department of Chemical Sciences and Technologies, Via della Ricerca Scientifica, University of Rome Tor Vergata.
    Vörös, Dimitrij
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Lange, Heikko
    Department of Chemical Sciences and Technologies, Via della Ricerca Scientifica, University of Rome Tor Vergata.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Crestini, Claudia
    Department of Chemical Sciences and Technologies, Via della Ricerca Scientifica, University of Rome Tor Vergata.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Isolation and Characterization of Organosolv and Alkaline Lignins from Hardwood and Softwood Biomass2016In: ACS Sustainable Chemistry and Engineering, ISSN 2168-0485, Vol. 4, no 10, p. 5181-5193Article in journal (Refereed)
    Abstract [en]

    Isolation of lignins from hardwood and softwood biomass samples, containing 26.1% and 28.1% lignin, respectively, has been performed with the use of alkaline and organosolv pretreatment methods. The effect of catalyst loading, ethanol content, particle size, and pretreatment time on the yields and properties of the isolated lignins were investigated. Alkaline lignins had higher carbohydrate content - up to 30% - and exhibited higher molecular weights in the range of 3000 Da, with a maximum phenolic hydroxyl content of 1 mmol g-1 for birch and 2 mmol g-1 for spruce. Organosolv lignins, on the other hand, showed high purity - 93% or higher - despite the more extensive biomass dissolution into the pretreatment medium; they also exhibited a lower range of molecular weights between 600 and 1600 Da depending on the source and pretreatment conditions. Due to the lower molecular weight, phenolic hydroxyl content was also increased, reaching as high as 4 mmol g-1 with a simultaneous decrease in aliphatic hydroxyl content as low as 0.6 mmol g-1. Efficient lignin dissolution of 62% for spruce and 69% for birch, achieved at optimal pretreatment conditions, was combined with extensive hemicellulose removal

  • 34.
    Parreiras, Lucas S.
    et al.
    University of Wisconsin.
    Breuer, Rebecca J.
    University of Wisconsin.
    Narasimhan, Ragothaman Avanasi
    University of Wisconsin.
    Higbee, Alan J.
    University of Wisconsin.
    Reau, Alex La
    University of Wisconsin.
    Tremaine, Mary T.
    University of Wisconsin.
    Qin, Li
    University of Wisconsin.
    Willis, Laura B.
    University of Wisconsin.
    Bice, Benjamin D.
    University of Wisconsin.
    Bonfert, Brandi L.
    University of Wisconsin.
    Pinhancos, Rebeca C.
    University of Wisconsin.
    Balloon, Allison J.
    University of Wisconsin.
    Uppugundla, Nirmal
    Michigan State University.
    Liu, Tongjun
    Michigan State University.
    Li, Chenlin
    Lawrence Berkeley National Laboratory.
    Tanjore, Deepti
    Lawrence Berkeley National Laboratory.
    Ong, Irene
    University of Wisconsin.
    Li, Haibo
    University of Wisconsin.
    Pohlmann, Edward L.
    University of Wisconsin.
    Serate, Jose
    University of Wisconsin.
    Withers, Sydnor T.
    University of Wisconsin.
    Simmons, Blake Alexander
    Joint BioEnergy Institute, California, Deconstruction Division, Berkeley.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Westphall, Michael S.
    University of Wisconsin.
    Coon, Joshua J.
    University of Wisconsin.
    Sato, Trey
    University of Wisconsin.
    Engineering and two-stage evolution of a lignocellulosic hydrolysate-tolerant Saccharomyces cerevisiae strain for anaerobic fermentation of xylose from AFEX pretreated corn stover2014In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, no 9, article id e107499Article in journal (Refereed)
    Abstract [en]

    The inability of the yeast Saccharomyces cerevisiae to ferment xylose effectively under anaerobic conditions is a major barrier to economical production of lignocellulosic biofuels. Although genetic approaches have enabled engineering of S. cerevisiae to convert xylose efficiently into ethanol in defined lab medium, few strains are able to ferment xylose from lignocellulosic hydrolysates in the absence of oxygen. This limited xylose conversion is believed to result from small molecules generated during biomass pretreatment and hydrolysis, which induce cellular stress and impair metabolism. Here, we describe the development of a xylose-fermenting S. cerevisiae strain with tolerance to a range of pretreated and hydrolyzed lignocellulose, including Ammonia Fiber Expansion (AFEX)-pretreated corn stover hydrolysate (ACSH). We genetically engineered a hydrolysate-resistant yeast strain with bacterial xylose isomerase and then applied two separate stages of aerobic and anaerobic directed evolution. The emergent S. cerevisiae strain rapidly converted xylose from lab medium and ACSH to ethanol under strict anaerobic conditions. Metabolomic, genetic and biochemical analyses suggested that a missense mutation in GRE3, which was acquired during the anaerobic evolution, contributed toward improved xylose conversion by reducing intracellular production of xylitol, an inhibitor of xylose isomerase. These results validate our combinatorial approach, which utilized phenotypic strain selection, rational engineering and directed evolution for the generation of a robust S. cerevisiae strain with the ability to ferment xylose anaerobically from ACSH.

  • 35.
    Phongpreecha, T.
    et al.
    Michigan State University, East Lansing, United States.
    Liu, J.
    Michigan State University, East Lansing, United States.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering. Montana State University, Bozeman, United States.
    Qi, Y.
    Michigan State University, East Lansing, United States.
    Adsorption of Lignin β-O-4 Dimers on Metal Surfaces in Vacuum and Solvated Environments2019In: ACS Sustainable Chemistry and Engineering, ISSN 2168-0485, no 2, p. 2667-2678Article in journal (Refereed)
    Abstract [en]

    Lignin hydrogenolysis has recently been studied extensively as it was shown to result in high monomer yields. Most of these reactions were conducted in liquid solvents, which have shown large impacts on product types and yields. Because adsorption is the first step to any heterogeneous catalyst reactions, this work aims to understand how solvent affects lignin adsorption on Ni(111) and Cu(111) surfaces. To achieve this, density functional theory calculations were employed to investigate β-O-4 lignin dimer (a model compound) adsorption conformations in both vacuum and liquid ethanol. In vacuum, it was found that lignin prefers to adsorb strongly on Ni(111) and weakly on Cu(111) with both aromatic rings parallel to the surface. Solvated adsorption was modeled using both implicit and explicit models. It was found that an explicit model is required to accurately describe the lignin-solvent interactions. With the explicit solvation model, it was predicted that the lignin dimer adsorbs on a Ni(111) surface but not on Cu(111). Furthermore, to circumvent the computationally expensive liquid interface calculations, a thermodynamic cycle method was developed to quickly estimate the solvated lignin dimer adsorption energy from the gas phase adsorption energy and the solvation energies. This model quantifies the effects from the solvent on lignin dimer adsorption, including the contributions from the lignin-solvent and the solvent-metal interactions, and suggests how to design both catalyst and solvent to tune lignin adsorption. 

  • 36.
    Phongpreecha, Thanaphong
    et al.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, USA.
    Hool, Nicholas C.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, USA.
    Stoklosa, Ryan J.
    Sustainable Biofuels and Co-Products Research Unit, Eastern Regional Research Center, USDA, ARS, 600 East Mermaid Lane, Wyndmoor, USA.
    Klett, Adam S.
    Department of Chemical and Biomolecular Engineering, Clemson University, Clemson, USA.
    Foster, Cliff E.
    DOE Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, USA.
    Bhalla, Aditya
    DOE Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, USA; Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, USA.
    Holmes, Daniel
    Department of Chemistry, Michigan State University, East Lansing, USA.
    Thies, Mark C.
    Department of Chemical and Biomolecular Engineering, Clemson University, Clemson, USA.
    Hodge, David B.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Department of Chemical and Biological Engineering, Montana State University, Bozeman, USA.
    Predicting lignin depolymerization yields from quantifiable properties using fractionated biorefinery lignins2017In: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270, Vol. 19, no 21, p. 5131-5143Article in journal (Refereed)
    Abstract [en]

    Lignin depolymerization to aromatic monomers with high yields and selectivity is essential for the economic feasibility of many lignin-valorization strategies within integrated biorefining processes. Importantly, the quality and properties of the lignin source play an essential role in impacting the conversion chemistry, yet this relationship between lignin properties and lignin susceptibility to depolymerization is not well established. In this study, we quantitatively demonstrate how the detrimental effect of a pretreatment process on the properties of lignins, particularly β-O-4 content, limit high yields of aromatic monomers using three lignin depolymerization approaches: thioacidolysis, hydrogenolysis, and oxidation. Through pH-based fractionation of alkali-solubilized lignin from hybrid poplar, this study demonstrates that the properties of lignin, namely β-O-4 linkages, phenolic hydroxyl groups, molecular weight, and S/G ratios exhibit strong correlations with each other even after pretreatment. Furthermore, the differences in these properties lead to discernible trends in aromatic monomer yields using the three depolymerization techniques. Based on the interdependency of alkali lignin properties and its susceptibility to depolymerization, a model for the prediction of monomer yields was developed and validated for depolymerization by quantitative thioacidolysis. These results highlight the importance of the lignin properties for their suitability for an ether-cleaving depolymerization process, since the theoretical monomer yields grows as a second order function of the β-O-4 content. Therefore, this research encourages and provides a reference tool for future studies to identify new methods for lignin-first biomass pretreatment and lignin valorization that emphasize preservation of lignin qualities, apart from focusing on optimization of reaction conditions and catalyst selection.

  • 37.
    Quershi, Nasib
    et al.
    United States Department of Agriculture, Agricultural Research Service, National Center for Agricultural Utilization Research, Bioenergy Research Unit, Peoria, IL.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Vertès, Alain
    London Business School.
    Biorefineries: Integrated Biochemical Processes for Liquid Biofuels2014Book (Refereed)
  • 38.
    Qureshi, Nasib
    et al.
    United States Department of Agriculture, Agricultural Research Service, National Center for Agricultural Utilization Research, Bioenergy Research Unit, Peoria, IL.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Vertès, Alain
    London Business School.
    Preface2014Other (Other academic)
  • 39.
    Scott, Felipe
    et al.
    School of Biochemical Engineering, Pontificia Universidad Católica de Valparaíso.
    Li, Muyang
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Williams, Daniel L.
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Conejeros, Raúl
    School of Biochemical Engineering, Pontificia Universidad Católica de Valparaíso.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Aroca, German
    School of Biochemical Engineering, Pontificia Universidad Católica de Valparaíso.
    Corn stover semi-mechanistic enzymatic hydrolysis model with tight parameter confidence intervals for model-based process design and optimization2015In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 177, p. 255-265Article in journal (Refereed)
    Abstract [en]

    Uncertainty associated to the estimated values of the parameters in a model is a key piece of information for decision makers and model users. However, this information is typically not reported or the confidence intervals are too large to be useful. A semi-mechanistic model for the enzymatic saccharification of dilute acid pretreated corn stover is proposed in this work, the model is a modification of an existing one providing a statistically significant improved fit towards a set of experimental data that includes varying initial solid loadings (10 to 25 % w/w) and the use of the pretreatment liquor and washed solids with or without supplementation of key inhibitors. A subset of 8 out of 17 parameters was identified, showing sufficiently tight confidence intervals to be used in uncertainty propagation and model analysis, without requiring interval truncation via expert judgment.

  • 40.
    Singh, Sandip K.
    et al.
    Chemical & Biological Engineering Department, Montana State University, Bozeman, Montana, United States.
    Savoy, Anthony W.
    Chemical & Biological Engineering Department, Montana State University, Bozeman, Montana, United States.
    Yuan, Zhaoyang
    Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, Michigan, United States.
    Luo, Hao
    Department of Chemistry, University of Wisconsin, Madison, Wisconsin, United States.
    Stahl, Shannon S.
    Department of Chemistry, University of Wisconsin, Madison, Wisconsin, United States.
    Hegg, Eric L.
    Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, Michigan, United States.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering. Chemical & Biological Engineering Department, Montana State University, Bozeman, Montana, United States.
    Integrated Two-Stage Alkaline-Oxidative Pretreatment of Hybrid Poplar. Part 1: Impact of Alkaline Pre-Extraction Conditions on Process Performance and Lignin Properties2019In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 58, no 35, p. 15989-15999Article in journal (Refereed)
    Abstract [en]

    We previously demonstrated that a two-stage pretreatment comprising of an alkaline pre-extraction followed by a Cu-catalyzed alkaline–oxidative treatment is effective at pretreating hardwoods under relatively mild reaction conditions. In this work, we focus on characterizing how biomass source and reaction conditions used during the alkaline pre-extraction impact the subsequent processing stages as well as lignin yields and properties. Specifically, three hybrid poplars were subjected to the first stage alkaline pre-extraction under various conditions including differences in time (15–300 min), temperature (95–155 °C), and alkali loadings (50–200 mg NaOH/g biomass), and the impact on total mass solubilization, lignin recovery, and lignin purity was determined. Empirical correlations were developed between reaction conditions and mass solubilization and lignin recovery during the pre-extraction stage. For select conditions, lignin properties were assessed and include β-O-4 content determined by 13C NMR, molecular mass distributions as determined by gel permeation chromatography, and susceptibility to depolymerization to aromatic monomers using thioacidolysis and formic acid catalyzed depolymerization. We found alkaline pre-extraction performed at higher temperatures generated lignins exhibiting lower contamination by polysaccharides, lower aromatic monomer yields from depolymerization, lower molar masses, and lower β-O-4 contents relative to the lower temperature pre-extractions. Finally, the pre-extracted biomass from select conditions was assessed for its response to the subsequent Cu-catalyzed alkaline–oxidative treatment and enzymatic hydrolysis. It was demonstrated that minor differences in delignification during pre-extraction have quantifiable impacts on the subsequent efficacy of the second stage of pretreatment and enzymatic hydrolysis with improved lignin removal during the first pre-extraction stage resulting in improved hydrolysis yields.

  • 41.
    Stoklosa, Ryan J.
    et al.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    del Pilar Orjuela, Andrea
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    da Costa Sousa, Leonardo
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Uppugundla, Nirmal
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Williams, Daniel L.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Dale, Bruce E.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Balan, Venkatesh
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Techno-economic comparison of centralized versus decentralized biorefineries for two alkaline pretreatment processes2017In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 226, p. 9-17Article in journal (Refereed)
    Abstract [en]

    In this work, corn stover subjected to ammonia fiber expansion (AFEX™) pretreatment or alkaline pre-extraction followed by hydrogen peroxide post-treatment (AHP pretreatment) were compared for their enzymatic hydrolysis yields over a range of solids loadings, enzymes loadings, and enzyme combinations. Process techno-economic models were compared for cellulosic ethanol production for a biorefinery that handles 2000 tons per day of corn stover employing a centralized biorefinery approach with AHP or a de-centralized AFEX pretreatment followed by biomass densification feeding a centralized biorefinery. A techno-economic analysis (TEA) of these scenarios shows that the AFEX process resulted in the highest capital investment but also has the lowest minimum ethanol selling price (MESP) at $2.09/gal, primarily due to good energy integration and an efficient ammonia recovery system. The economics of AHP could be made more competitive if oxidant loadings were reduced and the alkali and sugar losses were also decreased.

  • 42.
    Stoklosa, Ryan J.
    et al.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Fractionation and Improved Enzymatic Deconstruction of Hardwoods with Alkaline Delignification2015In: Bioenergy Research, ISSN 1939-1234, E-ISSN 1939-1242, Vol. 8, no 3, p. 1224-1234Article in journal (Refereed)
    Abstract [en]

    In this work, an alkaline delignification was investigated for several industrially relevant hardwoods to understand the kinetics of xylan solubilization and degradation and the role of residual lignin content in setting cell wall recalcitrance to enzymatic hydrolysis. Between 34 and 50 % of the xylan was solubilized during the heat-up stage of the pretreatment and undergoes degradation, depolymerization, as well as substantial disappearance of the glucuronic acid substitutions on the xylan during the bulk delignification phase. An important finding is that substantial xylan is still present in the liquor without degradation. Cellulose hydrolysis yields in the range of 80 to 90 % were achievable within 24–48 h for the diverse hardwoods subjected to delignification by alkali at modest enzyme loadings. It was found that substantial delignification was not necessary to achieve these high hydrolysis yields and that hybrid poplar subjected to pretreatment removing only 46 % of the lignin was capable of reaching yields comparable to hybrid poplar pretreated to 67 or 86 % lignin removal. Decreasing the lignin content was found to increase the initial rate of cellulose hydrolysis to glucose while lignin contents under approximately 70 mg/g original biomass were found to slightly decrease the maximum extent of hydrolysis, presumably due to drying-induced cellulose aggregation and pore collapse. Pretreatments were performed on woodchips, which necessitated a “disintegration” step following pretreatment. This allowed the effect of comminution method to be investigated for the three hardwoods subjected to the highest level of delignification. It was found that additional knife-milling following distintegration did not impact either the rate or extent of glucan and xylan hydrolysis.

  • 43.
    Tomek, Kyle J.
    et al.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Saldarriaga, Carlos Rafael Castillo
    Department of Chemical and Environmental Engineering, Universidad Nacional de Colombia, Bogotá.
    Velasquez, Fernando Peregrino Cordoba
    Department of Chemical and Environmental Engineering, Universidad Nacional de Colombia, Bogotá.
    Liu, Tongjun
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Whitehead, Timothy A.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Removal and upgrading of lignocellulosic fermentation inhibitors by in situ biocatalysis and liquid-liquid extraction2015In: Biotechnology and Bioengineering, ISSN 0006-3592, E-ISSN 1097-0290, Vol. 112, no 3, p. 627-632Article in journal (Refereed)
    Abstract [en]

    Hydroxycinnamic acids are known to inhibit microbial growth during fermentation of lignocellulosic biomass hydrolysates, and the ability to diminish hydroxycinnamic acid toxicity would allow for more effective biological conversion of biomass to fuels and other value-added products. In this work, we provide a proof-of-concept of an in situ approach to remove these fermentation inhibitors through constituent expression of a phenolic acid decarboxylase combined with liquid-liquid extraction of the vinyl phenol products. As a first step, we confirmed using simulated fermentation conditions in two model organisms, Escherichia coli and Saccharomyces cerevisiae, that the product 4-vinyl guaiacol is more inhibitory to growth than ferulic acid. Partition coefficients of ferulic acid, p-coumaric acid, 4-vinyl guaiacol, and 4-ethyl phenol were measured for long-chain primary alcohols and alkanes, and tetradecane was identified as a co-solvent that can preferentially extract vinyl phenols relative to the acid parent and additionally had no effect on microbial growth rates or ethanol yields. Finally, E. coli expressing an active phenolic acid decarboxylase retained near maximum anaerobic growth rates in the presence of ferulic acid if and only if tetradecane was added to the fermentation broth. This work confirms the feasibility of donating catabolic pathways into fermentative microorganisms in order to ameliorate the effects of hydroxycinnamic acids on growth rates, and suggests a general strategy of detoxification by simultaneous biological conversion and extraction.

  • 44.
    Williams, Daniel L.
    et al.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Crowe, Jacob D.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Ong, Rebecca G.
    Department of Chemical Engineering, Michigan Technological University, Houghton, MI.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Water Sorption in Pretreated Grasses as a Predictor of Enzymatic Hydrolysis Yields2017In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 245, p. 242-249Article in journal (Refereed)
    Abstract [en]

    This work investigated the impact of two alkaline pretreatments, ammonia fiber expansion (AFEX) and alkaline hydrogen peroxide (AHP) delignification performed over a range of conditions on the properties of corn stover and switchgrass. Changes in feedstock properties resulting from pretreatment were subsequently compared to enzymatic hydrolysis yields to examine the relationship between enzymatic hydrolysis and cell wall properties. The pretreatments function to increase enzymatic hydrolysis yields through different mechanisms; AFEX pretreatment through lignin relocalization and some xylan solubilization and AHP primarily through lignin solubilization. An important outcome was that while changes in lignin content in AHP-delignified biomass could be clearly correlated to improved response to hydrolysis, compositional changes alone in AFEX-pretreated biomass could not explain differences in hydrolysis yields. We determined the water retention value, which characterizes the association of water with the cell wall of the pretreated biomass, can be used to predict hydrolysis yields for all pretreated biomass.

  • 45.
    Williams, Daniel L.
    et al.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI, United States.DOE Great Lakes Bioenergy Research Center, Michigan State University, Madison, MI, United States.
    Ong, Rebecca G.
    DOE Great Lakes Bioenergy Research Center, Michigan State University, Madison, MI, United States.Department of Chemical Engineering, Michigan Technological University, Houghton, MI, United States.
    Mullet, John E.
    DOE Great Lakes Bioenergy Research Center, Michigan State University, Madison, MI, United States.Department of Biochemistry & Biophysics, Texas A&M University, College Station, TX, United States.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering. Department of Chemical & Biological Engineering, Montana State University, Bozeman, MT, United States.
    Integration of Pretreatment With Simultaneous Counter-Current Extraction of Energy Sorghum for High-Titer Mixed Sugar Production2019In: Frontiers in Energy Research, E-ISSN 2296-598X, Vol. 6, article id 133Article in journal (Refereed)
    Abstract [en]

    Sorghum (Sorghum bicolor L. Moench) offers substantial potential as a feedstock for the production of sugar-derived biofuels and biochemical products from cell wall polysaccharides (i.e., cellulose and hemicelluloses) and water-extractable sugars (i.e., glucose, fructose, sucrose, and starch). A number of preprocessing schemes can be envisioned that involve processes such as sugar extraction, pretreatment, and densification that could be employed in decentralized, regional-scale biomass processing depots. In this work, an energy sorghum exhibiting a combination of high biomass productivity and high sugar accumulation was evaluated for its potential for integration into several potential biomass preprocessing schemes. This included counter-current extraction of water-soluble sugars followed bymild NaOH or liquid hot water pretreatment of the extracted bagasse. A novel processing scheme was investigated that could integrate with current diffuser-type extraction systems for sugar extraction. In this approach, mild NaOH pretreatment (i.e., < 90 degrees C) was performed as a counter-current extraction to yield both an extracted, pretreated bagasse and a high-concentration mixed sugar stream. Following hydrolysis of the bagasse, the combined hydrolysates derived from cellulosic sugars and extractable sugars were demonstrated to be fermentable to high ethanol titers (> 8%) at high metabolic yields without detoxification using a Saccharomyces cerevisiae strain metabolically engineered and evolved to ferment xylose.

  • 46.
    Yuan, Zhaoyang
    et al.
    Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, Michigan, United States.
    Singh, Sandip Kumar
    Department of Chemical & Biological Engineering, Montana State University, Montana, United States.
    Bals, Bryan
    Michigan Biotechnology Institute, Lansing, Michigan, United States.
    Hodge, David B.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering. Department of Chemical & Biological Engineering, Montana State University, Bozeman, Montana , United States.
    Hegg, Eric L.
    Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, Michigan, United States.
    Integrated Two-Stage Alkaline–Oxidative Pretreatment of Hybrid Poplar. Part 2: Impact of Cu-Catalyzed Alkaline Hydrogen Peroxide Pretreatment Conditions on Process Performance and Economics2019In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 58, no 35, p. 16000-16008Article in journal (Refereed)
    Abstract [en]

    Two-stage alkaline/copper 2,2′-bipyridine-catalyzed alkaline hydrogen peroxide (Cu-AHP) pretreatment is an effective strategy for improving the enzymatic digestibility of hybrid poplar. To reduce the chemical inputs and processing costs associated with this process, we investigated the effect of increasing the temperature for both the alkaline pre-extraction and the Cu-AHP pretreatment stages. The results indicate that increasing the alkaline pre-extraction and the Cu-AHP pretreatment temperatures from 30 to 120 and 80 °C, respectively, allowed us to reduce both the pretreatment time of the Cu-AHP stage and the chemical loadings. Incubating alkaline pre-extracted hybrid poplar for 12 h with 10% NaOH (w/w biomass), 8% hydrogen peroxide (w/w biomass), and a Cu2+ and 2,2′-bipyridine (bpy) concentration of 1 mM yielded monomeric sugar yields of approximately 77% glucose and 66% xylose (based on the initial sugar composition) following enzymatic hydrolysis. Technoeconomic analysis (TEA) indicates that these changes to the two-stage alkaline/Cu-AHP pretreatment process could potentially reduce the minimum fuel selling price (MFSP) by more than $1.00 per gallon of biofuel compared to the reference case where both stages were conducted at 30 °C with higher chemical inputs.

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