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  • 1. Christakopoulos, Paul
    et al.
    Bhat, Mahalingeshwara K.
    Enzymatic synthesis of trisaccharides and alkyl β-d-glucosides by the transglycosylation reaction of β-glucosidase from Fusarium oxysporum1994In: International Journal of Biological Macromolecules, ISSN 0141-8130, E-ISSN 1879-0003, Vol. 16, no 6, p. 331-334Article in journal (Refereed)
    Abstract [en]

    Purified β-glucosidase from Fusarium oxysporum catalyses hydrolysis and transglycosylation reactions. By utilizing the transglycosylation reaction, trisaccharides and alkyl β-d-glucosides were synthesized under optimal conditions in the presence of various disaccharides and alcohols. The yields of trisaccharides and alkyl β-d-glucosides were 22–37% and 10–33% of the total sugar, respectively. The enzyme retained 70–80% of its original activity in the presence of 25% (w/v) methanol, ethanol and propanol. Thus, β-glucosidase from F. oxysporum appears to be an ideal enzyme for the synthesis of useful trisaccharides and alkyl β-d-glucosides.

  • 2. Christakopoulos, Paul
    et al.
    Katapodis, P.
    National Technical University of Athens.
    Kalogeris, E.
    National Technical University of Athens.
    Kekos, D.
    National Technical University of Athens.
    Macris, B.J.
    National Technical University of Athens.
    Stamatis, H.
    University of Ioannina.
    Skaltsa, H.
    School of Pharmacy, Panepistimiopolis, Zografou.
    Antimicrobial activity of acidic xylo-oligosaccharides produced by family 10 and 11 endoxylanases2003In: International Journal of Biological Macromolecules, ISSN 0141-8130, E-ISSN 1879-0003, Vol. 31, no 4-5, p. 171-175Article in journal (Refereed)
    Abstract [en]

    Acidic oligosaccharides were obtained from birchwood xylan by treatment with a Thermoascus aurantiacus family 10 and a Sporotrichum thermophile family 11 endoxylanases. The main difference between the products liberated by xylanases of family 10 and 11 concerned the length of the products containing 4-O-methyl-d-glucuronic acid. The xylanase from T. aurantiacus liberate from glucuronoxylan an aldotetrauronic acid as the shortest acidic fragment in contrast with the enzyme from S. thermophile, which liberated an aldopentauronic acid. Acidic xylooligosaccharides were separated from the hydrolysate by anion-exchange and size-exclusion chromatography (SEC) and the primary structure was determined by 13C NMR spectroscopy. The acidic xylo-oligosaccharides were tested against three Gram-positive and three Gram-negative aerobically grown bacteria, as well as against Helicobacterpylori. Aldopentauronic acid was proved more active against the Gram-positive bacteria and against H. pylori.

  • 3.
    Ghafari, Robab
    et al.
    Department of Wood and Paper Sciences and Technology, Faculty of Natural Resources, University of Tehran, Karaj, Iran.
    Jonoobi, Mehdi
    Department of Wood and Paper Sciences and Technology, Faculty of Natural Resources, University of Tehran, Karaj, Iran.
    Mohammadi Amirabad, Leila
    Marquette University, School of Dentistry, Milwaukee, WI, USA.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Taheri, Ahmad Reza
    Department of Plastic Surgery, Imam Khomeini Hospital, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
    Fabrication and characterization of novel bilayer scaffold from nanocellulose based aerogel for skin tissue engineering applications2019In: International Journal of Biological Macromolecules, ISSN 0141-8130, E-ISSN 1879-0003, Vol. 136, p. 796-803Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to fabricate a novel bilayer scaffold containing cellulose nanofiber/poly (vinyl) alcohol (CNF/PVA) to evaluate its potential use in skin tissue engineering. Here, the scaffolds were fabricated using a novel one-step freeze-drying technique with two different concentrations of the aforementioned polymers. FE-SEM analysis indicated that the fabricated scaffolds had interconnected pores with two defined pore size in each layer of the bilayer scaffolds that can recapitulate the two layers of the dermis and epidermis of the skin. Lower concentration of polymers causes higher porosity with larger pore size and increased water uptake and decreased mechanical strength. FTIR proved the presence of functional groups and strong hydrogen bonding between the molecules of CNF/PVA and the efficient crosslinking. The MTT assay showed that these nanofibrous scaffolds meet the requirement as a biocompatible material for skin repair. Here, for the first time, we fabricated bilayer scaffold using a novel one-step freeze-drying technique only by controlling the polymer concentration with spending less time and energy.

  • 4.
    Isarankura Na Ayutthaya, Siriorn
    et al.
    Division of Materials Technology, School of Energy, Environment and Materials, King Mongkut's University of Technology Thonburi.
    Tanpichai, Supachok
    Nanotec-KMUTT Center of Excellence on Hybrid Nanomaterials for Alternative Energy, King Mongkut's University of Technology (KMUTT)Thonburi, Bangkok .
    Sangkhun, Weradesh
    Nanotec-KMUTT Center of Excellence on Hybrid Nanomaterials for Alternative Energy (HyNAE), School of Energy, Environment and Materials, King Mongkut's University of Technology Thonburi, Bangkok.
    Wootthikanokkhan, Jatuphorn
    Nanotec-KMUTT Center of Excellence on Hybrid Nanomaterials for Alternative Energy, King Mongkut's University of Technology (KMUTT)Thonburi, Bangkok .
    Effect of clay content on morphology and processability of electrospun keratin/poly(lactic acid) nanofiber2016In: International Journal of Biological Macromolecules, ISSN 0141-8130, E-ISSN 1879-0003, Vol. 85, p. 585-595Article in journal (Refereed)
    Abstract [en]

    This research work has concerned the development of volatile organic compounds (VOCs) removal filters from biomaterials, based on keratin extracted from chicken feather waste and poly(lactic acid) (PLA) (50/50%w/w) blend. Clay (Na-montmorillonite) was also added to the blend solution prior to carrying out an electro-spinning process. The aim of this study was to investigate the effect of clay content on viscosity, conductivity, and morphology of the electrospun fibers. Scanning electron micrographs showed that smooth and bead-free fibers were obtained when clay content used was below 2 pph. XRD patterns of the electrospun fibers indicated that the clay was intercalated and exfoliated within the polymers matrix. Percentage crystallinity of keratin in the blend increased after adding the clay, as evidenced from FTIR spectra and DSC thermograms. Transmission electron micrographs revealed a kind of core-shell structure with clay being predominately resided within the keratin rich shell and at the interfacial region. Filtration performance of the electrospun keratin/PLA fibers, described in terms of pressure drop and its capability of removing methylene blue, were also explored. Overall, our results demonstrated that it was possible to improve process-ability, morphology and filtration efficiency of the electrospun keratin fibers by adding a suitable amount of clay.

  • 5.
    Makropoulou, M.
    et al.
    National Technical University of Athens.
    Christakopoulos, Paul
    Tsitsimpikou, C.
    National Technical University of Athens.
    Kekos, D.
    National Technical University of Athens.
    Kolisis, F.N.
    National Technical University of Athens.
    Macris, B.J.
    National Technical University of Athens.
    Factors affecting the specificity of beta-glucosidase from Fusarium oxysporum in enzymatic synthesis of alkyl-beta-D-glucosides1998In: International Journal of Biological Macromolecules, ISSN 0141-8130, E-ISSN 1879-0003, Vol. 22, no 2, p. 97-101Article in journal (Refereed)
    Abstract [en]

    Factors affecting the specificity of β-glucosidase from Fusarium oxysporum in enzymatic synthesis of alkyl-β-d-glucosidesFusarium oxysporumβ-glucosidase has been used to catalyze the production of alkyl-β-d-glucosides from various disaccharides, based on the transglucosylation reaction, in the presence of primary, secondary and tertiary alcohols as glucosyl acceptors. Primary alcohols were found to be the best acceptors. The influence of the glucosyl donor concentration, as well as the enzyme specificity towards the cleaved glucosidic bond and the aglucone part of the donor, have also been investigated. The enzyme does not exhibit regiospecificity and seems to be unspecific towards the aglucone part. The specificity of the β linkage has been confirmed by proton nuclear magnetic resonance (1H NMR) analysis.

  • 6.
    Mu, Liwen
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. Intelligent Composites Laboratory, Department of Chemical and Biomolecular Engineering, The University of Akron, Akron, OH, USA.
    Wu, Jian
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Chen, Minjiao
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    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.
    Zhu, Jiahua
    Intelligent Composites Laboratory, Department of Chemical and Biomolecular Engineering, The University of Akron, Akron, OH, USA.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Two important factors of selecting lignin as efficient lubricating additives in poly (ethylene glycol): Hydrogen bond and molecular weight2019In: International Journal of Biological Macromolecules, ISSN 0141-8130, E-ISSN 1879-0003, Vol. 129, p. 564-570Article in journal (Refereed)
    Abstract [en]

    Lignin, one of the most abundant natural polymers, has been successfully used as an effective lubricant additive with high value. The chemical structure of lignin is very diverse and strongly affected by both the source of lignin (i.e. plant species) and the lignin extraction process. In this work, a series of lignin from different biomass sources (hard or soft wood) and extraction process (organosolv with or without acid catalyst) has been successfully incorporated into poly(ethylene glycol) (PEG) and fortified lubricating properties were achieved. The effects of different lignin on the rheological, thermal and tribological properties of the lignin/EG lubricants were systematically investigated by different characterization techniques. Lignin in PEG significantly improves the lubricating property, where a wear reduction of 93.8% was observed. The thermal and lubrication properties of the PEG lubricants filled with different kinds of lignin are tightly related to the synergistic state of hydrogen bonding and molecular weight distribution. Lignin with broader molecular weight distribution and higher hydroxyl content shows better adhesion on metal surfaces and strengthened lubricating film, which could be used as the efficient lubricating additives. This work provides a criterion for selecting appropriate lignin as the efficient lubricant additive and accelerates the application of lignin.

  • 7.
    Salehpour, Shoboo
    et al.
    Department of Wood and Paper Science and Technology, Faculty of Natural Resources, University of Tehran, Karaj.
    Jonoobi, Mehdi
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Wood and Paper Science and Technology, Faculty of Natural Resources, University of Tehran, Karaj.
    Ahmadzadeh, Masoud
    Department of Plant Protection, Faculty of Agriculture and Natural Resources, University of Tehran, Karaj.
    Siracusa, Valentina
    Department of Chemical Science, University of Catania.
    Rafieian, Fatemeh
    Food Science Department, Agriculture College, Isfahan University of Technology.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Biodegradation and ecotoxicological impact of celluose nanocomposites in municipal solid waste composting2018In: International Journal of Biological Macromolecules, ISSN 0141-8130, E-ISSN 1879-0003, Vol. 111, p. 264-270Article in journal (Refereed)
    Abstract [en]

    Biodegradable nanocomposites were prepared from polyvinyl alcohol (PVA) and cellulose nanofiber (CNF) by using liquid nitrogen, freeze drying and hot press techniques. The effect of CNF content on the biodegradability of the films was investigated by visual observation, scanning electron microscopy (SEM), weight loss, CO2 evolution, differential scanning calorimetry, measuring the amount of mineralized carbon of the specimens buried in municipal solid waste. Ecotoxicity was evaluated by plants growth tests with cress and spinach. The results confirmed that the weight loss of nanocomposites was lower than that of neat PVA because of the zigzag pathways of microorganisms in the CNF presence. The SEM analysis showed extensive surface roughness and cracks for all samples, indicating the initiation of biodegradation. The CO2 evolution decreased with increasing CNF content from 0% to 10% and then, increased with further increase in the filler content (up to 30 wt%). The crystallinity of the PVA and its nanocomposites increased as a function of time because of the amorphous parts degradation. Preliminary results of the ecotoxicological test revealed that all the nanocomposites and neat PVA did not generate any negative effects on germination or development of the studied vegetal species.

  • 8.
    Sanakis, Y.
    et al.
    University of Ioannina.
    Mamma, D.
    Institute of Materials Science.
    Christakopoulos, Paul
    Stamatis, H.
    University of Ioannina.
    Catechol 1,2-dioxygenase from Pseudomonas putida in organic media: an electron paramagnetic resonance study2003In: International Journal of Biological Macromolecules, ISSN 0141-8130, E-ISSN 1879-0003, Vol. 33, no 1-3, p. 101-106Article in journal (Refereed)
    Abstract [en]

    The ability of an isolated isozyme of catechol 1,2-dioxygenase from Pseudomonas putida DSM 437 to function in a non-aqueous environment was investigated. The lyophilized enzyme is able to keep its catalytic function catalyzing the oxidation of catechol in n-hexane. Electron paramagnetic resonance (EPR) spectroscopy at liquid helium temperatures was applied to compare the properties of the non-heme iron of the enzyme in the organic solvent and in the aqueous solution. The catalytic performance of the enzyme in the organic solvent is correlated with the spectroscopic properties of the non-heme iron.

  • 9.
    Vardakou, Maria
    et al.
    National Technical University of Athens.
    Katapodis, Petros
    National Technical University of Athens.
    Samiotaki, Martina
    Biomedical Research Center, Vari.
    Kekos, Dimitris
    National Technical University of Athens.
    Panayotou, George
    Biomedical Research Center, Vari.
    Christakopoulos, Paul
    Mode of action of family 10 and 11 endoxylanases on water-unextractable arabinoxylan2003In: International Journal of Biological Macromolecules, ISSN 0141-8130, E-ISSN 1879-0003, Vol. 33, no 1-3, p. 129-134Article in journal (Refereed)
    Abstract [en]

    Microbial endo-β-1,4-xylanases (EXs, EC 3.2.1.8) belonging to glycanase families 10 and 11 differ in their action on water-unextractable arabinoxylan (WU-AX). WU-AX was incubated with different levels of a Thermoascus aurantiacus family 10 and a Sporotrichum thermophile family 11 endoxylanases. At 10 g l−1 arabinoxylan, enzyme concentrations (KE values) needed to obtain half-maximal hydrolysis rates (Vmax values) were 4.4 nM for the xylanase from T. aurantiacus and 7.1 nM for the xylanase from S. thermophile. Determination of Vmax/KE revealed that the family 10 enzyme hydrolysed two times more efficiently WU-AX than the family 11 enzyme. Molecular weights of the products formed were assessed and separation of feruloyl-oligosaccharides was achieved by anion-exchange and size-exclusion chromatography (SEC). The main difference between the feruloylated products by xylanases of family 10 and 11 concerned the length of the products containing feruloyl-arabinosyl substitution. The xylanase from T. aurantiacus liberated from WU-AX a feruloyl arabinoxylodisaccharide (FAX2) as the shortest feruloylated fragment in contrast with the enzyme from S. thermophile, which liberated a feruloyl arabinoxylotrisaccharide (FAX3). These results indicated that different factors govern WU-AX breakdown by the two endoxylanases.

  • 10.
    Vardakou, Maria
    et al.
    National Technical University of Athens.
    Palop, Carmen Nueno
    Institute of Food Research, Norwich.
    Gasson, Michael
    Institute of Food Research, Norwich.
    Narbad, Arjan
    Institute of Food Research, Norwich.
    Christakopoulos, Paul
    In vitro three-stage continuous fermentation of wheat arabinoxylan fractions and induction of hydrolase activity by the gut microflora2007In: International Journal of Biological Macromolecules, ISSN 0141-8130, E-ISSN 1879-0003, Vol. 41, no 5, p. 584-589Article in journal (Refereed)
    Abstract [en]

    In vitro fermentations were carried out by using a model of the human colon to stimulate microbial activities of gut bacteria. The model consisted of a three-stage culture system. Bacterial populations were evaluated under the effect of three types of arabinoxylan, a nonstarch polysaccharide derived from wheat, the water-unextractable arabinoxylan fraction (WU-AX), WU-AX pretreated with exogenous xylanase and the soluble water-extractable arabinoxylan fraction (WE-AX). The xylanase pretreated (WU-AX) had a stimulatory effect upon colonic bifidobacteria throughout all three vessels. Counts of Bacteroides spp. and Clostridium spp. were also both significantly reduced. Addition of the WU-AX substrates to the first vessel resulted in induction of bacterial synthesis of extracellular hydrolytic enzymes xylanase and ferulic acid esterase which are both required for bacterial metabolism of WU-AX; this induction was significantly greater with the xylanase treated WU-AX.

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