Development Of Biorefineries Research Articles

Highly selective and stable ZnO-supported bimetallic RuSn catalyst for the hydrogenation of octanoic acid to octanol

• Octanoic acid was converted over RuSn supported on ZnO. • High conversion (99.4 %) and selectivity to octanol (93.0 %) were achieved. • Ru 3 Sn 7 alloy phase was responsible for the high hydrogenation activity. • Esterification was suppressed by optimizing the reaction condition. • RuSn/ZnO was exceptionally robust over 1000 h. The chemoselective hydrogenation of biomass-derived carboxylic acids is promising for the development of biorefineries. Herein, the selective conversion of octanoic acid to octanol over bimetallic RuSn/ZnO in a fixed-bed continuous reactor system, is reported. Almost complete conversion (99.4 %) of octanoic acid was achieved, with a remarkably high selectivity to octanol (93.0 %), when using specific reaction conditions (300°C, a weight hourly space velocity (WHSV) of 2 h −1 , and 30 atm H 2 ). Characterizations of the catalysts by BET, CO pulse chemisorption, ICP-AES, XRD, XPS and STEM-EDS revealed that the addition of Sn to Ru/ZnO resulted in the formation of a Ru 3 Sn 7 alloy phase as well as SnO x . Comparison with Ru/ZnO catalyst gives an insight that the presence of Ru 3 Sn 7 alloy was most likely the active site and it significantly improved the hydrogenation activity and selectivity to octanol. The SnO x and ZnO favored the formation of octyl octanoate by esterification of the formed octanol and octanoic acid, although it was successfully suppressed by optimizing the reaction conditions. Long-term stability tests revealed that RuSn/ZnO retained its activity for 1000 h with no coke formation. This study reveals the potential of RuSn/ZnO for the valorization of medium-chain fatty acids into value-added chemicals.

Membrane-Based Harvesting Processes for Microalgae and Their Valuable-Related Molecules: A Review.

The interest in microalgae production deals with its role as the third generation of feedstock to recover renewable energy. Today, there is a need to analyze the ultimate research and advances in recovering the microalgae biomass from the culture medium. Therefore, this review brings the current research developments (over the last three years) in the field of harvesting microalgae using membrane-based technologies (including microfiltration, ultrafiltration and forward osmosis). Initially, the principles of membrane technologies are given to outline the main parameters influencing their operation. The main strategies adopted by the research community for the harvesting of microalgae using membranes are subsequently addressed, paying particular attention to the novel achievements made for improving filtration performance and alleviating fouling. Moreover, this contribution also gives an overview of the advantages of applying membrane technologies for the efficient extraction of the high added-value compounds in microalgae cells, such as lipids, proteins and carbohydrates, which together with the production of renewable biofuels could boost the development of more sustainable and cost-effective microalgae biorefineries.

Interdependence between lignocellulosic biomasses, enzymatic hydrolysis and yeast cell factories in biorefineries.

SummaryBiorefineries have a pivotal role in the bioeconomy scenario for the transition from fossil‐based processes towards more sustainable ones relying on renewable resources. Lignocellulose is a prominent feedstock since its abundance and relatively low cost. Microorganisms are often protagonists of biorefineries, as they contribute both to the enzymatic degradation of lignocellulose complex polymers and to the fermentative conversion of the hydrolyzed biomasses into fine and bulk chemicals. Enzymes have therefore become crucial for the development of sustainable biorefineries, being able to provide nutrients to cells from lignocellulose. Enzymatic hydrolysis can be performed by a portfolio of natural enzymes that degrade lignocellulose, often combined into cocktails. As enzymes can be deployed in different operative settings, such as separate hydrolysis and fermentation (SHF) or simultaneous saccharification and fermentation (SSF), their characteristics need to be combined with microbial ones to maximize the process. We therefore reviewed how the optimization of lignocellulose enzymatic hydrolysis can ameliorate bioethanol production when Saccharomyces cerevisiae is used as cell factory. Expanding beyond biofuels, enzymatic cocktail optimization can also be pivotal to unlock the potential of non‐Saccharomyces yeasts, which, thanks to broader substrate utilization, inhibitor resistance and peculiar metabolism, can widen the array of feedstocks and products of biorefineries.

Biofuels and biorefineries: Development, application and future perspectives emphasizing the environmental and economic aspects

The fossil fuel utilization adversely affected the environmental health due to the rising emission levels of greenhouse gases. Consequently, the challenges of climate change loaded great stress on renewable energy sources. It is noted that extreme consumption of fossil fuels increased the earth temperature by 1.9 °C that adversely influenced the life and biodiversity. Biorefinery is the sustainable process for the production of biofuels and other bio-products from biomass feedstock using different conversion technologies. Biofuel is an important component of renewable energy sources contributing to overall carbon-neutral energy system. Studies reported that on global scale, over 90% of petroleum goods could be produced from renewable resources by 2023, whereas, 33% chemicals, and 50% of the pharmaceutical market share is also expected to be bio-based. This study details the brief review of operation, development, application, limitations, future perspectives, circular bioeconomy, and life cycle assessment of biorefinery. The economic and environmental aspects of biofuels and biorefineries are briefly discussed. Lastly, considering the present challenges, the future perspectives of biofuels and biorefineries are highlighted.

Subcritical water pretreatment for agave bagasse fractionation from tequila production and enzymatic susceptibility

This work focuses on the effect of subcritical water pretreatment conditions on agave bagasse chemical composition, biomass fractionation, and enzymatic hydrolysis obtained from the different tequila production processes. The pretreatment was carried out in a batch pressurized reactor within an isothermal regime. The operational conditions for subcritical water pretreatment were (150–190 °C) and (10–50 min). The best operational conditions were selected, based on the increased cellulose content (>50%) in the pretreated solid phase. The conditions for 190 °C for 50 and 30 min of pretreated agave bagasse solids were chosen for enzymatic hydrolysis susceptibility (15 FPU/g of the substrate). The maximum conversion yield (cellulose to glucose) during enzymatic hydrolysis achieved was up to 61.62% (5.86 g/L) in industrial bagasse at 72 h and initial saccharification rate was 0.34 g/(L*h) at 12 h. This study indicates that the agave bagasse is a promising raw material in the development of second-generation biorefineries.

Co‐utilization of amino acid‐rich wastes and glycerol for microbial lipid production

AbstractMicrobial lipids are considered to be potential raw materials for biodiesel production. However, the costs of such a process remain high due to the use of expensive feedstocks for microbial lipid production. The meat industry and biodiesel refineries generate amino acid (AA) wastes and crude glycerol, respectively, which could be explored as relatively cheap feedstocks for oleaginous yeasts. Unfortunately, AA wastes have a high nitrogen content and crude glycerol contains several impurities, discouraging microbial lipid production. Here, glycerol was co‐used with AA, or with AA blends with compositional profiles matching those of different meats, so that the media had favorable carbon‐to‐nitrogen (C/N) ratios to promote AA conversion into lipids using the oleaginous yeast Cryptococcus curvatus ATCC 20509 under two‐stage culture conditions. Co‐utilization of glycerol and AA resulted in improved lipid production. The highest lipid yield of 20.9 g 100 g–1 was achieved with lysine and glycerol, where the lipid yield was 13.9 g 100 g–1, using an AA blend of similar composition to sheep viscera and glycerol. The lipid products comprised over 93% of 16 and 18 carbon‐containing fatty acids, showing high potential for biodiesel production. The co‐use of glycerol with AA improved AA conversion into lipids while decreasing the inhibitory effects at relatively high AA concentrations. The utilization of crude glycerol and AA‐rich wastes from the meat industry could help both the development of biorefineries and waste minimization. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

Biorefining for olive wastes management and efficient bioenergy production

The potential of olive wastes for development of a multi-product biorefinery was investigated. Different parts of olive wastes, i.e., stone, pomace, leaves, and wood, were subjected to liquid hot water, organosolv, and acid-catalyzed organosolv (ACO) pretreatments prior to bioconversion through three different scenarios. The first scenario, i.e., anaerobic digestion of substrates for biogas production, yielded 219.3 m3 biomethane per hectare of olive trees, equated to 247.4 L gasoline. The highest methane production of 103.3 m3 was attributed to liquid hot water pretreated wood and ACO increased methane yield for leaf and stone samples by 200 and 33%, respectively. The second scenario, i.e., fermentation of wastes for bioethanol production, resulted in 295.9 L bioethanol per hectare of olive trees, equivalent to 196.1 L gasoline. Organosolv pretreated wood with 82.9% production yield and 152.5 L bioethanol constitutes this plan's dominant part. The ACO pretreatment improved fermentation yield for pomace and stone samples by 49% and 53%, respectively. The third scenario, included the utilization of olive wastes in bioethanol production, anaerobic digestion of fermentation residues, and lignin separation, resulted in 295.9 L bioethanol, 137.2 m3 biomethane, and 347.1 kg lignin, equated with 521.6 L gasoline. Furthermore, the remaining oil content in pomace and stone samples was 17% and 20%, respectively, which could be used for biodiesel production. Overall, olive wastes processing through an integrated biorefinery plant with multiple products significantly improved the energy recovery of the whole plant.

An optimal biorefinery development for pectin and biofuels production from orange wastes without enzyme consumption

Orange wastes, including peel and pulp, were used as a biorefinery feedstock to produce pectin, ethanol, and biogas. The orange wastes were subjected to dilute acid treatment with sulfuric acid (1% w/v) at 94, 100, 140, and 180 °C for 60, 30, and 0 min. The sulfuric acid treatment was performed for pectin extraction, sugars hydrolysis, and lignocellulose pretreatment. The pectin was extracted from the hydrolysate, the liquor was used to produce ethanol, and the pretreated solid was anaerobically digested to produce biogas. The highest pectin extraction yield was 24.7 % (w/w) from orange peel and 23.7 % (w/w) from pulp, which was obtained from the supernatants of treatment at 94 °C for 60 min. Fourier transfer infrared spectrometer results confirmed the similar characteristics of the extracted pectin to a commercial product. The galacturonic acid content (an indicator of pectin purity) of pectin extracted from orange peel was 70.2 % and from orange pulp was 69.9 %, at the optimum conditions. The pectin obtained from the acid treatment at 94 °C for 60 min had a degree of esterification higher than 69 %, whereas it was less than 45 % for that obtained after treatment at 140 °C for 30 min. The maximum ethanol yields of 81.5 % (from peel) and 82.9 % (from pulp) were achieved from the hydrolysate of the acid treatment at 140 °C for 30 min. The highest methane yields were 176.8 mL/g volatile solids (from the untreated peel) and 191.8 mL/g volatile solids (from the untreated pulp). Overall, the maximum total product value was 2,472.9 USD/t orange wastes, which was achieved from dilute acid treatment at 94 °C for 60 min. At the optimal conditions for high production of pectin, without any enzyme consumption, 244 kg of pectin, 26.5 L of ethanol, and 36 m3 of methane were produced from 1 t of orange wastes.

Challenges of sustainable industrial transformation: Swedish biorefinery development and incumbents in the emerging biofuels industry

AbstractThis paper investigates the transformation challenges related to incumbent industries caused by technology development and industry convergence in the transition to a bioeconomy in the context of Swedish biorefinery development. It involves the emergence of new value chains and several incumbent industries such as the pulp and paper industry, the oil refinery sector, the chemical process industry, and the heat and power sector. In 2019, Sweden had Europe's largest share of biofuels in the transport sector, roughly 20% on an energy basis, and this share has increased by around 300% during the last decade. At the same time, domestic production has stalled, and even though Sweden has beneficial conditions for biofuel production, the share of biofuel that is imported or based on imported feedstock has recently ranged between 85% and 90%. We discuss three transformation challenges: (i) inertia and lack of absorptive capacity creating lock‐in effects at the organizational level; (ii) weak and inefficient actor networks at the industry level; and (iii) contradictory policy instrument mixes and lack of coordination at the government level. The findings underscore the need for policy integration and alignment across various policy domains, and an increased focus on policy mixes that can stimulate the emergence of more disruptive innovations and value chains. There is also a need for industrial initiatives, such as improving absorptive capacity and strengthening actor networks, to help build the value chains needed to realize a sustainable bioeconomy. 2021 The Authors. Biofuels, Bioproducts and Biorefining published by Society of Industrial Chemistry and John Wiley & Sons Ltd

Lignocellulosic biorefineries: The current state of challenges and strategies for efficient commercialization

Lignocellulosic biomass is the most abundant and sustainable feedstock available globally. As a source of the polysaccharides, cellulose and hemicellulose, it can be converted into biofuels and other platform chemicals. This article highlights some important aspects that needs to be focused upon for the commercial development of lignocellulosic biorefineries. Although, lignocellulosic biomass offers clear value in terms of its green advantages and sustainability, there has been very low commercial success at industrial production levels. This can be attributed to a few key factors such as an irregular biomass supply chain, inefficient or complex pre-treatment and saccharification technologies, and scale up challenges leading to high capital and operating expenditures. Moreover, techno-economic studies performed on lignocellulosic biorefineries have revealed that process complexity is the most detrimental factor prohibiting scale-up. Although there have been several research efforts funded both by the public and private sectors, biomass valorization into biofuels and chemicals remains a technical and economical challenge. This review examines the global drivers towards the advancements of lignocellulosic biorefineries, technical and operational challenges for industrialization and future directions towards overcoming them.

Techno-Economic Analysis of Integrating Soybean Biorefinery Products into Corn-Based Ethanol Fermentation Operations

With the development of agricultural biorefineries and bioprocessing operations, understanding the economic efficiencies and environmental impacts for these have gradually become popular for the deployment of these industrial processes. The corn-based ethanol and soybean oil refining industries have been examined extensively over the years, especially details of processing technologies, including materials, reaction controls, equipment, and industrial applications. The study focused on examining the production efficiency changes and economic impacts of integrating products from the enzyme-assisted aqueous extraction processing (EAEP) of soybeans into corn-based ethanol fermentation processing. Using SuperPro Designer to simulate production of corn-based ethanol at either 40 million gallons per year (MGY) or 120 MGY, with either oil separation or no oil removal, we found that indeed integrating soy products into corn ethanol fermentation may be slightly more expensive in terms of production costs, but economic returns justify this integration due to substantially greater quantities of ethanol, distillers corn oil, and distillers dried grains with solubles being produced.

Identification of novel pentose transporters in Kluyveromyces marxianus using a new screening platform.

ABSTRACTThe capacity of yeasts to assimilate xylose or arabinose is strongly dependent on plasma membrane transport proteins. Because pentoses comprise a substantial proportion of available sugars in lignocellulosic hydrolysates, their utilisation is centrally important for the development of second generation biorefineries. Relatively few native pentose transporters have been studied and there is intense interest in expanding the repertoire. To aid the identification of novel transporters, we developed a screening platform in the native pentose-utilising yeast Kluyveromyces marxianus. This involved the targeted deletion of twelve transporters of the major facilitator superfamily (MFS) and application of a synthetic biology pipeline for rapid testing of candidate pentose transporters. Using this K. marxianus ΔPT platform, we identified several K. marxianus putative xylose or arabinose transporter proteins that recovered a null strain's ability to growth on these pentoses. Four proteins of the HGT-family were able to support growth in media with high or low concentrations of either xylose or arabinose, while six HXT-like proteins displayed growth only at high xylose concentrations, indicating solely low affinity transport activity. The study offers new insights into the evolution of sugar transporters in yeast and expands the set of native pentose transporters for future functional and biotechnological studies.

Nanomechanics of Lignin-Cellulase Interactions in Aqueous Solutions.

Efficient enzymatic hydrolysis of cellulose in lignocellulose to glucose is one of the most critical steps for the production of biofuels. The nonproductive adsorption of lignin to expensive cellulase highly impedes the development of biorefinery. Understanding the lignin-cellulase interaction mechanism serves as a vital basis for reducing such nonproductive adsorption in their practical applications. Yet, limited report is available on the direct characterization of the lignin-cellulase interactions. Herein, for the first time, the nanomechanics of the biomacromolecules including lignin, cellulase, and cellulose were systematically investigated by using a surface force apparatus (SFA) at the nanoscale in aqueous solutions. Interestingly, a cation-π interaction was discovered and demonstrated between lignin and cellulase molecules through SFA measurements with the addition of different cations (Na+, K+, etc.). The complementary adsorption tests and theoretical calculations further confirmed the validity of the force measurement results. This finding further inspired the investigation of the interaction between lignin and other noncatalytic-hydrolysis protein (i.e., soy protein). Soy protein was demonstrated as an effective, biocompatible, and inexpensive lignin-blocker based on the molecular force measurements through the combined effects of electrostatic, cation-π, and hydrophobic interactions, which significantly improved the enzymatic hydrolysis efficiencies of cellulose in pretreated lignocellulosic substrates. Our results offer quantitative information on the fundamental understanding of the lignin-cellulase interaction mechanism. Such unraveled nanomechanics provides new insights into the development of advanced biotechnologies for addressing the nonproductive adsorption of lignin to cellulase, with great implications on improving the economics of lignocellulosic biorefinery.

Development of a Phaeodactylum tricornutum biorefinery to sustainably produce omega-3 fatty acids and protein

Phaeodactylum tricornutum is a genetically well-studied microalga but commercial production of omega-3 fatty acids and protein had not been established. Here, a biorefinery platform to cost-effectively culture, harvest and process this diatom has been developed. Using a sea salt substitute supplemented with magnesium enabled low-cost land-based cultivation, reaching biomass yields of 0.17 g L−1day−1 and 340 g m−2day−1 in free-standing outdoor photobioreactors. pH-induced auto-flocculation in bioreactors or open ponds followed by solar drying was most cost-effective to harvest dry biomass. Lipids extracted by organic solvents accounted for 27.3% per dry biomass. Ethanol was the safest and most suitable option for a biorefinery yielding 92% of extractable omega-3 eicosapentaenoic acid (EPA) and 40.9% of protein in the defatted biomass. Using Central Composite Design, optimized alkaline extraction recovered 60.4% of total protein. A cost comparison to Nannochloropsis microalgae showed that EPA-rich oil and protein for human consumption are the most viable products with potentially lower EPA production costs. This study demonstrates that land-based P. tricornutum cultivation can provide a sustainable source of omega-3 fatty acid without putting pressures on marine bioresources.

Development of a Methodology for the Synthesis of Biorefineries Based on Incremental Economic and Exergetic Return on Investment.

Colombia is experiencing significant growth in its agricultural areas, its diverse production chains make the country an excellent candidate in the development of biorefineries, and as a result, there is an increasing need to take full advantage of biomass and obtain high value-added by-products from waste. In this sense, biorefineries are presented as a great alternative for the use of biomass; however, the methodologies of biorefinery synthesis lack a parameter that limits the growth of production lines under incremental exergetic and economic returns. This research develops a biorefinery synthesis methodology using an African palm biorefinery as a case study; a novel approach is developed to facilitate a stop criterion for biorefinery expansion through a combined consideration of economic incremental returns (IROI) and exegetical returns of investment (ExROI), avoiding unnecessary plant expansions or new processes that are not profitable or adequate in terms of useful energy. The development of this methodology required simulations in Aspen Plus software and technical-economic and exergetic evaluation with an incremental approach of four scenarios in Excel. The base case is palm oil production from African palm clusters. The second case includes the production of palm kernel oil and palm cake from residues. The third case implements the production of hydrogen based on other residues from the base case. The last case study incorporates the preceding case and the addition of biodiesel and glycerin production from palm oil. Case 3 exhibits a higher economic performance with an IROI of 42.98%; in terms of exergy, case 2 exhibits considerable improvements over the base case, with an ExROI of 158%. A parameter called the exergo-economic weighted incremental return on investment (IExWROI) was obtained, evidencing a 75% improvement in case 2 compared to the base case. The new indicator aims to provide a more comprehensive approach to biorefinery design by optimization of economic and exergetic returns, contributing a new alternative for decision-making in regard to plant design, plant expansion projects, and implementation of subprocesses.

Hydrogel-Forming Algae Polysaccharides: From Seaweed to Biomedical Applications.

With the increasing growth of the algae industry and the development of algae biorefinery, there is a growing need for high-value applications of algae-extracted biopolymers. The utilization of such biopolymers in the biomedical field can be considered as one of the most attractive applications but is challenging to implement. Historically, polysaccharides extracted from seaweed have been used for a long time in biomedical research, for example, agarose gels for electrophoresis and bacterial culture. To overcome the current challenges in polysaccharides and help further the development of high-added-value applications, an overview of the entire polysaccharide journey from seaweed to biomedical applications is needed. This encompasses algae culture, extraction, chemistry, characterization, processing, and an understanding of the interactions of soft matter with living organisms. In this review, we present algae polysaccharides that intrinsically form hydrogels: alginate, carrageenan, ulvan, starch, agarose, porphyran, and (nano)cellulose and classify these by their gelation mechanisms. The focus of this review further lays on the culture and extraction strategies to obtain pure polysaccharides, their structure-properties relationships, the current advances in chemical backbone modifications, and how these modifications can be used to tune the polysaccharide properties. The available techniques to characterize each organization scale of a polysaccharide hydrogel are presented, and the impact on their interactions with biological systems is discussed. Finally, a perspective of the anticipated development of the whole field and how the further utilization of hydrogel-forming polysaccharides extracted from algae can revolutionize the current algae industry are suggested.

Acid hydrolysis-based sugarcane bagasse biorefining for levulinic acid production: Dynamic mechanistic modeling under varying operating conditions

The study on the lignocellulosic material conversion into bio-based platform chemicals, such as levulinic acid (LA), is one of the most promising routes to promote the development of advanced biorefineries. In this work, a dynamic mechanistic model is developed to simulate the LA production from lignocellulosic material. A wide operating range is used to estimate the parameters of the reaction kinetics. Because multi-parameter estimation problem is complex, a genetic algorithm-based optimization procedure is used to determine the optimum parameters values. Measurements are obtained for various reaction times (0 - 45 min) temperatures (150 – 200 °C) and acid concentration of 7.0 % w/v H2SO4. The calculated reaction rates for the state variables, concentrations of LA, glucose, 5-hydroxymethylfurfural and humins are used to construct the dynamic mechanistic model. The prediction of measured state variables was particularly accurate, as determined by the root mean square error (RMSE) and correlation coefficient (R2). Therefore, a satisfactory agreement between experimental LA yield of 57.2 mol% and computed LA yield of 56.4 mol% was achieved (at 200 °C, 7.0 % w/v H2SO4, 45 min). The proposed methodology drives the systematic development of an industrially reliable dynamic mechanistic model for LA production from sugarcane bagasse as a means to increase the LA yields in the biorefinery.

Current perspective on improved fermentative production and purification of fungal cellulases for successful biorefinery applications: a brief review

Cellulolytic enzymes play the most indispensable and centralized role in the hydrolysis of cellulosic material. Effective enzymatic hydrolysis is one of the major prerequisites in the development of a successful lignocellulosic biorefinery. However, the high cost of cellulase production yet remains to be the major bottleneck for large-scale commercial realization of lignocellusic bio-refinery. In addition, the lack of specificity and inconsistent bioconversion efficiencies of enzymes have restricted their applications towards bioconversion of narrow range of substrates. In view of addressing such bottlenecks associated with cellulase applications and further to improve the applicability of cellulase enzyme in various industrial processes, the current review essentially captures up-to-date information of various strategies adopted for the prospective production and purification of cellulase enzymes. Some holistic strategies deliberated in this review, which evolved over time and have brought about notable improvements in the final titer, yield, specificity, and productivity of the cellulolytic enzymes. It includes utilization of low-cost industrial or agricultural wastes for onsite production, application of enzyme, strain improvement through mutagenic, metabolic engineering and genetic engineering approaches, application of suitable bioprocess optimization techniques, development of ideal bioreactor configuration based on mode of fermentation process, and adaptation of the most intensive purification schemes. Additionally, to address the present existing challenges, more emphasizes have been concentrated towards economically sustainable and comprehensive production strategies of the enzyme.

Identification of the molecular determinants driving the substrate specificity of fungal lytic polysaccharide monooxygenases (LPMOs)

Understanding enzymatic breakdown of plant biomass is crucial to develop nature-inspired biotechnological processes. Lytic polysaccharide monooxygenases (LPMOs) are microbial enzymes secreted by fungal saprotrophs involved in carbon recycling. LPMOs modify biomass by oxidatively cleaving polysaccharides, thereby enhancing the efficiency of glycoside hydrolases. Fungal AA9 LPMOs are active on cellulose, but some members also display activity on hemicelluloses and/or oligosaccharides. Although the active site subsites are well defined for a few model LPMOs, the molecular determinants driving broad substrate specificity are still not easily predictable. Based on bioinformatic clustering and sequence alignments, we selected seven fungal AA9 LPMOs that differ in the amino-acid residues constituting their subsites. Investigation of their substrate specificities revealed that all these LPMOs are active on cellulose and cello-oligosaccharides, as well as plant cell wall–derived hemicellulosic polysaccharides, and carry out C4 oxidative cleavage. The product profiles from cello-oligosaccharide degradation suggest that the subtle differences in amino-acid sequence within the substrate-binding loop regions lead to different preferred binding modes. Our functional analyses allowed us to probe the molecular determinants of substrate binding within two AA9 LPMO subclusters. Many wood-degrading fungal species rich in AA9 genes have at least one AA9 enzyme with structural loop features that allow recognition of short β-(1,4)–linked glucan chains. Time-course monitoring of these AA9 LPMOs on cello-oligosaccharides also provides a useful model system for mechanistic studies of LPMO catalysis. These results are valuable for the understanding of LPMO contribution to wood decaying process in nature and for the development of sustainable biorefineries.

Hydrogen production by Enterobacter sp. LBTM 2 using sugarcane bagasse hemicellulose hydrolysate and a synthetic substrate: understanding and controlling toxicity

Abstract Sugars released by thermochemical pretreatment of lignocellulosic biomass are possible substrate for hydrogen production. However, the major drawback for bacterial fermentation is the toxicity of weak acids and furan derivatives normally present in such substrate. This study aimed to investigate the metabolism involved in hydrogen production by the isolate Enterobacter LBTM2 using 10, 20 and 30-fold diluted synthetic (SH) and sugarcane bagasse hemicellulose (SBH) hydrolysates. In addition, the effects of acetic acid, formic acid and furfural on the bacterial metabolism, as well as detoxification of SBH with activated carbon and molecularly imprinted polymers on the hydrogen production were assessed. The results showed the best hydrogen yield was 0.46 mmol H2/mmol sugar for 20-times diluted SH, which was 2.3-times higher than obtained in SBH experiments. Bacterial growth and hydrogen production were negatively affected by 0.8 g/L of acetic acid when added alone, but were totally inhibited when formic acid (0.4 g/L) and furfural (0.3 g/L) were also supplied. However the maximum hydrogen production of SBH20 has duplicated when 3% of powdered activated carbon was added to the SBH experiment. The results presented herein can be helpful in understanding the bottlenecks in biohydrogen production and could contribute towards development of lignocellulosic biorefinery.