The global waste crisis is a significant concern driven by urbanization and economic expansion. Untreated waste poses major environmental, economic, and societal challenges, especially affecting agriculture and industry. Addressing this crisis necessitates innovative waste management strategies and sustainable practices to mitigate the impending waste burden on ecosystems and societies worldwide. Recent advancements in biofuels and biochemicals intensified research into the conversion of biogenic waste into bio-carboxylic acid/volatile fatty acids (VFAs), driven by the dual imperatives of sustainable waste management and renewable resource development. This study presents a comparative analysis of three waste streams: cheese whey from the cheese-making industry, lignocellulosic brewery spent grains (BSG), and agricultural by-products like wheat straw (WS) assessing their efficacy in carboxylic acid production by mixed culture fermentation. Each substrate produced a diverse array of carboxylic acids, including acetic, propionic, butyric, valeric, iso-valeric, and caproic acids exhibiting unique fermentation efficiencies in carboxylic acid production. The experimental results reveal distinct fermentation efficiencies, the highest concentration of short-chain carboxylic acids (SCCA) production of 11.84 gCOD per L from CW, alongside a medium-chain carboxylic acid (MCCA) production of 3.95 gCOD per L. Notably, despite the lignocellulosic composition of the substrates, both BSG and WS demonstrated substantial and competitive yields of SCCA and MCCA. Specifically, BSG produced 10.68 gCOD per L of SCCA and 3.54 gCOD per L of MCCA, while WS yielded 11.51 gCOD per L of SCCA and 3.84 gCOD per L of MCCA. These findings highlight the viability of lignocellulosic substrates for carboxylic acid production, suggesting significant opportunities for enhancing bioprocessing strategies in biochemical and industrial applications. Taxonomic analysis of microbial communities showed a significant predominance of Firmicutes, Bacteroidota, and Actinobacteriota. The Clostridiaceae family exhibited dominance across all reactors, with respective abundances of 82.72%, 27.67%, and 61.29%. The BSG uniquely showcased an enrichment of Lactobacillaceae (23.86%), Ruminococcaceae (7.72%), and Prevotellaceae (3.24%). Key genera contributing to carboxylic acid production included Clostridium sensu stricto 1, Romboutsia, and Enterococcus. This diversity highlights the influence of substrate composition on microbial community structure, highlighting the intricate relationships between substrate nature and microbial metabolites suggesting that strategic substrate selection could optimize fermentation efficiency and enhance product yield.

This study demonstrates a green method to produce low-density cellulose using organosolv pretreated pulp, which also yields high-purity fractions of hemicelluloses and lignin that can be processed further to obtain different chemicals. A base-catalyzed organosolv pretreatment was employed on Norway spruce woodchips to release the cellulose fibrils, which were used to make low-density (20 kg/m3) porous foams (98%). Sodium hydroxide was used as a catalyst, ranging from 0.25 to 1.5 M. The fibers obtained from these pretreatment conditions were characterized and correlated to the foam formation and properties. Furthermore, the samples were compared to foams made from commercially available unbleached and bleached sulfite pulp. A simple production technique was employed by rapidly agitating cellulose pulp with surfactant and additives to induce air into the system. The cellulose fibers arranged around the bubbles and formed a 3-D network upon drying. The lignin content and fiber aspect ratio of the organosolv fibers showed a positive correlation to the foam formation and stability. The foams presented good mechanical resistance (75%), and this property was tuned by the additives. High moisture adsorption tendency and comparably slower scavenging of antioxidant molecules were hypothesized to be due to the position of lignin in the interiors of the cell wall; these properties make the organosolv foams interesting for bioactive packaging applications. 

The production of biogas through anaerobic digestion (AD) of organic-renewable feedstocks is recognized as a viable solution within the renewable energy sector. Biogas typically contains a methane concentration ranging from 60 to 70%, presenting a significant opportunity for energy generation. However, the co-generated carbon dioxide (CO2), which constitutes approximately 30–40% of biogas, poses challenges to overall energy efficiency, thus necessitating the implementation of purification methods to enhance methane concentrations. It is noteworthy that the production of one ton of biomethane results in the generation of approximately two tons of biogenic CO2. This reality opens avenues for carbon capture, storage, and valorization strategies. The biogas industry is beginning to recognize CO2 not merely as a byproduct to be discarded, but as a valuable resource for the synthesis of biomethane, chemicals, fuels, and even building materials. There is a growing interest in utilizing biogenic CO2 as a climate-friendly feedstock, with “bio-Carbon Capture and Utilization” (bio-CCU) practices facilitating the development of sustainable fuels, chemicals, and materials. The article extends to various methods of valorization for biogenic CO2, providing an analysis of techniques for separating and upgrading CO2 derived from biogas. This assessment encompasses both physical and biological methodologies within the carbon capture, utilization, and storage (CCUS) framework. The article further demonstrates both in-situ and ex-situ processes, including biological methodologies that employ microorganisms for CO2 conversion, as well as thermo-physicochemical processes that transform CO2 into biobased products. Additionally, the article demonstrates the economic and environmental advantages associated with the strategic utilization of biogenic CO2. Repurposing this resource is vital for achieving sustainability goals, particularly in renewable energy sectors, where it can significantly enhance energy efficiency and reduce waste. Finally, the article emphasizes the importance of these practices in climate change mitigation, advocating for a circular economy that prioritizes carbon reuse over atmospheric emissions, thus contributing to the advancement of a sustainable future.

Plastic waste, especially from packaging, poses major recycling challenges due to the presence of mixed polymers, which often result in inconsistent blends that are unsuitable for reuse in food-grade applications. Chemical recycling, particularly alkaline hydrolysis, offers a promising solution in the case of chemically reactive polymers, such as polyesters, with poly(ethylene terephthalate) (PET) being one of the dominant plastics suitable for both mechanical and chemical recycling. Mechanical recycling is currently used for the largest part of PET recycling, due to the fact that turning the polymer back into its monomeric building blocks requires catalysts, elevated temperatures, or prolonged reaction times. This study presents a recently developed Heated High-Ethanol Alkaline Aqueous (HHeAA) process that enables efficient, catalyst-free PET hydrolysis under milder conditions. Nearly complete hydrolysis was achieved within just 20 min at 90 °C using a loading of 0.624 g of NaOH/g of PET. The process was successfully scaled up with commercial PET bottles, achieving full hydrolysis while significantly reducing the liquid-to-solid ratio from 20 to just 5 L/kg. These results highlight the industrial potential of the HHeAA method as a more sustainable and energy-efficient alternative for PET recycling and chemical reuse and in turn reduced environmental impact.

Microbial electrosynthesis (MES) offers a sustainable alternative for the production of platform chemicals from CO2. Label-free Raman spectroscopy can provide direct insights into biomolecular changes in MES, reflecting metabolic activity and production. In this study defined co-cultures of electro-active bacteria, i.e. Sporomusa ovata and Clostridium carboxidivorans, were investigated by confocal resonance Raman micro-spectroscopy tuned to 532 nm to gain insights into the microbial processes of biomarkers involved in the Wood-Ljundahl pathway. The results were correlated to high-performance liquid chromatography (HPCL) and optical density measurements regarding the production rate of acetate, butyrate, ethanol and butanol. Pre-processed difference Raman spectra of co-cultures from S. ovata and C. carboxidivorans at ratios 1:10, 10:1, and 1:1 were compared to monocultures on day 1 and 2, revealing substantial variations in Raman intensity and thus the relative metabolic activity of NADH, NAD+, ferredoxin and cytochrome c. Such information may point to high metabolic activity at the start of acetate, butyrate, ethanol, and butanol production followed by a steady state at day four. This was verified by Raman difference spectra between fresh cultures and > 4 days old cultures, indicating a similar degree of metabolic activity after a certain time during ongoing production. Interestingly, the Raman spectra did not reveal any differences in metabolism depending on feedstocks, i.e. CO₂ and H₂ versus betaine or different ratios of co-cultures that were significantly more productive. This qualitative study demonstrates that resonance Raman spectroscopy is a viable tool for metabolic investigations of microbial electrosynthesis systems with potential for in situ investigations.

CO2 absorption in aqueous alkaline solutions promoted by carbonic anhydrase (CA) has received increased attention as a solution for post-combustion CO2 capture. In particular, accelerated weathering has emerged as an alternative approach for CO2 capture, mimicking nature’s way to sequestrate CO2. In this study, an evolved CA from Desulfovibrio vulgaris was immobilized on magnetic nanoparticles (MNPs) offering a promising solution for the effective enzyme separation and recovery from complex and heterogeneous reaction media. The immobilization yields were high (86–98 %) and MNPs-DvCA8.0 were characterized based on standardized CO2 release and CO2 absorption assays and compared to the free enzyme. As a following step, MNPs-DvCA8.0 were applied as promoter in the accelerated weathering of insoluble lime mud, originating as a residue from a paper and pulp industry. MNPs-DvCA8.0 could be efficiently separated, washed and reused for up to 10 consecutive reaction cycles, offering a biocatalyst productivity equal to 2.83 g captured CO2/g CA opposite to the free enzyme that offered only 1.01 g captured CO2/g CA. CA immobilization could offer a mitigation strategy for the non-selective adsorption of the free enzyme on lime mud particles during the CO2 capturing reaction. The highly reproducible and robust immobilization method, that provides material separation based on its magnetic properties, could be a viable solution for the recovery of enzyme and its separation from the lime mud slurry, aiding in obtaining a highly pure solution rich in bicarbonate, as product.

The escalating global environmental crisis demands transformative biotechnological solutions that are both sustainable and scalable. This perspective advocates Data-Driven Synthetic Microbes (DDSM); engineered microorganisms designed through integrating omics, machine learning, and systems biology to tackle challenges like PFAS degradation, greenhouse gas mitigation, and sustainable biomanufacturing. DDSMs offer a rational framework for developing robust microbial systems, reshaping the future of synthetic biology toward environmental resilience and circular bioeconomy.

Carbonic anhydrases (CAs) have been proved as a highly efficient and selective promoter for conventional Carbon Capture Utilization and Storage (CCUS) industrial processes. The aim of this work was to demonstrate a high-throughput screening system for detecting engineered CAs with resistance to common inhibitors (SO42-, SO32-, NO3-, NO2-) present as major impurities in post-combustion flue gases, maintaining their initial thermostability. We established a screening protocol on solid and liquid assays for selecting mutants generated with error-prone PCR (epCA8.0) maintaining the thermostability of the parent DvCA8.0 but having improved resistance to flue gas inhibitors. A library of around 1000 mutants was created. The mutant E12 (G7D) showed 50 % increased stability for a mix of inhibitors corresponding to total concentration of 300–600 mM and 65 % increased stability to 150 mM, compared to the parent DvCA8.0. To our knowledge, this is the first time that a CA was evolved by protein engineering methods to increase its stability to common flue gas inhibitors. Additionally, we have established a premise for screening and characterization of CA libraries, which has not been clearly addressed previously, as presence of ionic inhibitors significantly change the pH of enzyme assays, while the nature of such screening assays is pH dependent. We envision that this study will open the pathway for the development of highly resistant CAs in the near future, overcoming stability and cost issues that are associated with their limited application in CCUS technologies.

Whiteleg shrimp (Penaeus vannamei) is currently facing significant challenges related to severe disease outbreaks. As the importance of the host–microbiota relationship is being revealed, modulating this relationship has become a key strategy in disease management. Xylooligosaccharides (XOS)—short-chain sugar molecules—have been gaining attention for their potential health benefits in the prebiotics field. In this study, an XOS-rich extract from Salicornia ramosissima was incorporated into shrimp feeds to evaluate its impact on gut health, with the main focus on gut proteomics and microbiota. XOS were incorporated at 0.1% (XOS_0.1) and 1% (XOS_1) concentrations, and a 14-day feeding trial, followed by a bacterial challenge with Vibrio harveyi, was performed. The effects of XOS were evaluated by assessing zootechnical parameters, gene expression in the hepatopancreas, and gut microbiota and proteome. The results showed no significant differences in zootechnical parameters and gene expression after the 14-day trial between animals fed XOS diets and control. However, shrimp fed XOS_1 showed an increased diversity of the microbial communities in the gut when compared with those fed control. Also, known shrimp gut symbionts, such as Ruegeria, Leisingera, and Demequina, were significantly enriched in groups fed XOS after the feeding trial. XOS also modulated the regulation of proteins in the gut. Nevertheless, stressful conditions appear to alter the effects of XOS and the dynamics of gut bacteria. Further studies are warranted to understand the impacts of long-term inclusion of XOS extracts, especially on health-related parameters and disease resistance.

Apatite and rare earth elements (REEs) are vital to the European Union’s economic growth and resource security, given their essential roles in fertilizers, green technologies, and high-tech applications. To meet rising demand and reduce reliance on imports, the exploitation of domestic deposits has become increasingly important. This study investigates the beneficiation potential of ore from a carbonatite complex (Finland), focusing on the recovery of fluorapatite concentrate through froth flotation. This research addresses two key objectives: evaluating the potential for REE enrichment alongside fluorapatite concentration using conventional anionic and amine-based reagents, and assessing separation efficiency when partially substituting the most effective conventional collectors with bio-based organosolv lignin nanoparticles. Adequate recovery rates for apatite and REEs were achieved using common anionic collectors, such as hydroxamate and sarcosine, yielding P grades of 23.4% and 21.5%, and recoveries of 96.4% and 89.2%, respectively. Importantly, concentrate quality remained stable with up to a 30% reduction in conventional collectors and the addition of organosolv lignin. Bench-scale trials further validated the approach, demonstrating that lanthanum and cerium recoveries exceeded 71%, alongside satisfactory apatite recovery. Lignin nanoparticles were observed to interact with both minerals; however, the interaction was more pronounced in the case of phlogopite, which exhibited a markedly greater increase in surface hydrophilicity following treatment, suggesting a stronger affinity or surface modification effect, which was beneficial to the performance of the separation process.