Features of promising technologies for pretreatment of lignocellulosic biomass

Enhanced hemicellulose retention in lignocellulosic biomass fractionation with ethylene glycol-regulated deep eutectic solvent

Fractionation of lignocellulosic biomass into carbohydrates (cellulose, hemicellulose) and lignin is essential for advancing biorefinery processes. However, achieving high retention of hemicellulose during pretreatment remains a significant challenge. In this study, an ethylene glycol (EG)-regulated deep eutectic solvent (DES) strategy was employed for corncob fractionation. The addition of EG increased hemicellulose retention from 55.7% to 77.9%. Additionally, delignification and cellulose retention reached up to 88.8% and 88.1%, respectively. Density functional theory analysis indicated that strong hydrogen bonds between DES-EG and lignin are the primary driving force for delignification. Molecular dynamics simulations demonstrated that the incorporation of EG significantly weakens the interaction energies between solvent and hemicellulose. This protective effect preserves the structural integrity of glycosidic linkages and hydroxyl groups in hemicellulose. This work presents a sustainable solution to mitigate hemicellulose loss, offering a promising advancement for eco-friendly biomass pretreatment.

Simultaneous Determination of Yeast Inhibitors 5‑HMF and Furfural in Hydrolyzed Lignocellulosic Biomass using HPLC-PDA

The lignocellulosic biomass acid hydrolysis process, for either pretreatment or saccharification purposes, involves temperature and acidity, which can lead to carbohydrate dehydration into furfuraldehydes, such as 5-hydroxymethylfurfural (5-HMF) and furfural. Unfortunately, these compounds can reduce the biomass quality for biofuel production, potentially inhibiting yeast fermentation, which converts sugars into ethanol, leading to low yields. Given the need to control these substances, a methodology for the simultaneous determination of 5-HMF and furfural via high-performance liquid chromatography (HPLC) was developed and validated to monitor the formation of these unwanted byproducts directly after the hydrolysis process of the Hevea brasiliensis lignocellulosic matrix. The method showed adequate selectivity for both analytes. Linearity was confirmed by analysis of variance (p < 0.05) for 5-HMF and furfural, with excellent correlation coefficients: R 2 = 0.99984 in the 0.1-50 μg·mL-1 range for 5-HMF, and R 2 = 0.99956 in the 0.1-25 μg·mL-1 range for furfural, with low limits of detection and quantification: 0.1981 and 0.6002 μg·mL-1 for 5-HMF, and 0.1585 and 0.4802 μg·mL-1 for furfural, respectively. The method also demonstrated accuracy, with recovery rates in fortified samples between 100.7 and 104.9% for 5-HMF and 97.54 and 100.4% for furfural. Precision, divided into repeatability and intermediate precision, showed both values for RSD < 15%. Additionally, the method demonstrated robustness, maintaining expected performance when subjected to small variations. The developed method proved to be a quick, effective, and reliable approach for quantifying 5-HMF and furfural in the hydrolyzed lignocellulosic biomass, successfully applied to 43 real samples without the need for complex pretreatment and with a shorter run time and high sensitivity. This makes it suitable for routine monitoring and supports more practical, scalable, and both time and cost-effective strategies for optimizing biomass conversion and bioethanol production.

High-level production of free fatty acids from lignocellulose hydrolysate by co-utilizing glucose and xylose in yeast

Lignocellulose bio-refinery via microbial cell factories for chemical production represents a renewable and sustainable route in response to resource starvation and environmental concerns. However, the challenges associated with the co-utilization of xylose and glucose often hinders the efficiency of lignocellulose bioconversion. Here, we engineered yeast Ogataea polymorpha to effectively produce free fatty acids from lignocellulose. The non-oxidative branch of the pentose phosphate pathway, and the adaptive expression levels of xylose metabolic pathway genes XYL1, XYL2 and XYL3, were systematically optimized. In addition, the introduction of xylose transporter and global regulation of transcription factors achieved synchronous co-utilization of glucose and xylose. The engineered strain produced 11.2 g/L FFAs from lignocellulose hydrolysates, with a yield of up to 0.054 g/g. This study demonstrated that metabolic rewiring of xylose metabolism could support the efficient co-utilization of glucose and xylose from lignocellulosic resources, which may provide theoretical reference for lignocellulose biorefinery.

Influence of vapothermal and hydrothermal pre-treatment on anaerobic degradability of lignocellulosic biomass

This study compares the biogas potential of solid common reed residues after undergoing vapothermal and hydrothermal pre-treatment, accompanied by a compositional and structural biomass characterization. In a pre-test series, a design of experiments approach was used to determine the influence of the initial biomass water content during vapothermal pre-treatment on the biogas yield. In the main test series, common reed was pre-treated hydrothermally (i.e., in liquid water) and vapothermally (i.e., in saturated steam) while varying temperature and residence time. The initial biomass water content significantly impacted the biogas potential, with an optimum at a value of 32 to 46 wt-%FM. In the main test series, unlike the residence time, temperature significantly impacted the subsequent anaerobic digestion. Vapothermal pre-treatment had a narrow temperature optimum while hydrothermal pre-treatment led to a biogas increase in a broader temperature range. The optimum temperature of both methods was 170 °C, where methane potentials increased by 28 % (vapothermal) and 36 % (hydrothermal) compared to the untreated sample. Considering the mass loss occurring during the pre-treatment, this increase was still 18 % for vapothermal pre-treatment, while it diminished the increase to 6 % for hydrothermal pre-treatment. Overall, vapothermal pre-treatment produced a similar amount of biogas under comparable conditions, but was less susceptible to carbon loss, and, according to an estimation of the required process energy, may offer energy savings compared to hydrothermal pre-treatment.

Expression and biochemical characterization of a novel NAD+-dependent xylitol dehydrogenase from the plant endophytic fungus Trichodermagamsii

Xylitol dehydrogenase (XDH; EC 1.1.1.9), encoded by the XYL2 gene, is a key enzyme in the fungal xylose metabolic pathway. In this work, a putative XDH from the plant endophytic fungus Trichoderma gamsii (TgXDH) was hetero-expressed in Escherichia coli BL21(DE3), purified to the homogeneity, and biochemically characterized. Sequence analysis revealed that TgXDH is 363 amino acids long and belongs to the zinc-containing medium-chain alcohol dehydrogenase superfamily. The size-exclusion chromatography analysis and SDS-PAGE showed that the purified recombinant TgXDH had a native molecular mass of ∼155 kDa and was composed of four identical subunits of molecular mass of ∼39 kDa. The optimum temperature and pH of this enzyme were 25 °C and pH 9.5, respectively. Kinetic analysis showed that it is an NAD+-dependent enzyme that has a polyol substrate preference (based on kcat/Km) in the order xylitol > ribitol ≈ d-sorbitol. The Km values for NAD+ with these three polyols ranged from 0.23 to 0.70 mM. Moreover, TgXDH showed high substrate affinities as compared to most of its homologs. The Km values for xylitol, ribitol, and d-sorbitol were 5.23 ± 0.68 mM, 8.01 ± 1.22 mM, and 12.34 ± 1.37 mM, respectively. Collectively, the results will contribute to understanding the biochemical properties of a novel XDH from the filamentous fungi and provide a promising XDH for industrial production of ethanol.

Research progress on organic acid pretreatment of lignocellulose

Lignocellulosic biomass is a naturally occurring, renewable resource that is utilized to produce a variety of high-value-added products, such as fuels, acids, and building block chemicals. The pretreatment of lignocellulosic biomass is a crucial step in the deconstruction and fractionation of its components. Organic acids, such as formic, acetic, lactic, and maleic acids, have been widely studied for their effectiveness in lignocellulose pretreatment. Organic acid-based pretreatment techniques are gaining increased attention due to their ability to selectively separate hemicellulose and cellulose, promote oligomer formation, and minimize byproducts. This paper presents a comprehensive review of the various advancements in the science and application of organic acids for the pretreatment of lignocellulose. Furthermore, the significant challenges of organic acid recovery after pretreatment are highlighted, and different recovery methods are discussed. The future challenges related to utilizing organic acids for lignocellulose pretreatment are summarized, with a strong emphasis on adopting a sustainable approach to converting valuable bioresources into renewable products.

Extraction and chemical features of wood hemicelluloses: A review

Hemicelluloses have immense potential for applications in diverse fields, especially in polymeric materials. This review critically examines biomass treatment technologies, encompassing chemical, mechanical, and combined approaches to disrupt plant cell walls and enhance hemicellulose accessibility and solubility. The choice of a treatment method depends on factors like purpose, biomass composition, and economic and environmental considerations. Hemicelluloses extracted from wood are composed from up to 11 monomer units, most of them "neutral" monosaccharides (glucose, mannose etc.) but a couple "charged" (uronic acids). The average compositions of wood hemicelluloses change with the type of wood; the accuracy is not known. The content of "charged" monosaccharides may particularly suffer from underestimation due to strong hydrolysis. The chemical composition of intact wood hemicelluloses has never been determined: it is thus not known if hemicelluloses in wood are a mixture of several "simple" polysaccharides (such as glucomannans) or complex polysaccharides with up to 11 monomer units in the same macromolecule. Currently determined molecular weights (MW) of hemicelluloses range from 500 to 1,000,000 Da. The precision and accuracy of MWs are not known, primarily due to column inconsistency in analyzing anionic and neutral polymers. A combination of chromatography SEC methods and detectors is required for standardization.

Directed hydrogenolysis of "cellulose-to-ethylene glycol" using a Ni-WO x based catalyst

Biomass is an important renewable resource in nature, and cellulose is a crucial component within it. The chemically directed conversion of cellulose into ethylene glycol offers a green alternative to traditional petroleum-based production methods. In this study, a multifunctional Ni-WO x /SAPO-11 catalyst was designed. By optimizing the processing parameters of catalysts and the reaction conditions of them, it was demonstrated that this catalyst could efficiently catalyze cellulose into alcohol products through a series of tandem reactions such as hydrolysis, retro-aldol condensation, and hydrogenation under relatively mild conditions. The yield of ethylene glycol climbed from 4% (at 180 °C) to 66.6% (at 240 °C) with the increase of reaction temperature. Characterization (XPS, TEM, TPD/TPR) revealed that a reduction temperature of 500 °C maximized Brønsted acidity and W5+/W6+ ratios, enhancing C-C cleavage efficiency. Further increases in the reduction temperature would weaken the Brønsted acid on the surface of SAPO-11, but its surface area would also increase (mainly in the form of mesopores). The uniformly dispersed elemental tungsten could form new acidic sites on the catalyst surface; in combination with active Ni0, this high-temperature reduced catalyst could achieve the direct hydrogenolysis of cellulose to produce ethylene glycol, benefiting the efficient utilization of lignocellulosic biomass in the future.

The potential of Trichoderma asperellum for degrading wheat straw and its key genes in lignocellulose degradation

This study explored Trichoderma asperellum's lignocellulose degradation potential in wheat straw (WS) and NaOH-treated WS via solid-state fermentation (SSF) over 30 days. Compared to the control, WS treated with T. asperellum (TW) and NaOH-treated WS with T. asperellum (TN) showed increased dry matter loss rates of 15.67 and 15.76%, respectively. Cellulose degradation reached 33.51 and 28.00%, while hemicellulose degradation increased to 31.56 and 63.86%. Crude protein (CP) content rose to 10.96 and 7.44%, and reducing sugar content to 10.86 and 12.41 mg/g, respectively. T. asperellum effectively reduced lignocellulose content and enhanced substrate nutrition, supporting subsequent uses of WS as fertilizer, feed, or for bioethanol production. Enzymatic activity and structural analyses were performed to further confirm the lignocellulose-degrading ability of T. asperellum and to analyze the degradation mechanisms. Transcriptomic analysis revealed that, compared with the control group, the TN group had 4,548, 4,399, and 6,051 differentially expressed genes (DEGs) at 5, 10, and 30 days, respectively, mainly involved in cellulose and hemicellulose degradation, carbohydrate metabolism, carbohydrate transport, glycoside hydrolases, and polysaccharide binding. T. asperellum can modify lignin by expressing dye-decolorizing peroxidase genes, and multiple key genes were identified for further research into its genetic regulation in lignocellulose degradation.

Applications of modified lignocellulose and its composites prepared by different pretreatments in biomedicine: A review

Lignocellulosic biomass represents one of the most abundant renewable biological resources on earth. Despite its current underutilization as a source of high-value chemicals, it has promising applications in biomedical and other fields. Presently, lignocellulose is predominantly transformed into high-value-added products, e.g. cellulose nanocrystals (CNCs), cellulose nanofibers (CNFs), etc., through a variety of physical, chemical and biological methods. The mechanical properties and biocompatibility of these products make them important as vital components in drug delivery agents and tissue engineering materials in the biomedical field. This review offers a comprehensive overview of the underexploited lignocellulosic biomass, the main pretreatment methods for converting it into valuable compounds, and the associated limitations. It also highlights the emerging applications of these compounds in the biomedical field, including sensors, wound dressings, excipients, and artificial skin. In addition, current commercialized products and related regulations are discussed, and future research advancements in this field are also envisaged.

Lignin nano/micro-particles from agricultural biomasses: Developing direct precipitation for integrated biorefinery

The state-of-the-art, simple and scalable methods for lignin micro-/nano-particles recovery from agricultural biomasses were evaluated in this review. Being non-wood biomasses, these materials can be easily fibrillated, supporting the usage of mild soda or organic solvent pretreatment. Different approaches in particle recovery were compared to conclude that the bottom-up approach facilitates smaller particles towards the nano-size range whereas mechanical treatment can act as a supporting method to increase uniformity and reduce particle sizes after bottom-up precipitation. By combining with the pretreatment steps, direct one-pot lignin micro-/nano-particle recovery can be achieved using the lignin-containing black liquor or organosolv liquor. These lignin micro-/nano-particles can then be applied as high-value functional products in cosmetics, pharmaceuticals, environmental remediation, and energy sectors. The systematic evaluation of lignin micro-/nano-particles recovery from agricultural biomasses in this review can support the full utilization of these natural resources to aim towards a circular agriculture.

Production of protein-rich fungal biomass from pistachio dehulling waste using edible Neurospora intermedia

Pistachio dehulling waste, known as Pistachio byproduct mixture (PBM), is a valuable resource that is often overlooked. An effective sustainable approach involves utilizing this agricultural waste through a fermentation process using edible filamentous fungi, demonstrating potential applications in nutrition and animal feed. The focus of this study was on converting PBM extract obtained from a hot water extraction pre-treatment into a protein-rich fungal biomass of Neurospora intermedia. The optimal conditions for growth were achieved at 72 h, pH 5.5, and 30 °C which are achieved by one-factor-at-a-time approach (OFAT), resulting in 6.7 g/L of dried fungal biomass, with a protein content of 20.4%. The conversion efficiency, expressed as grams of fungal biomass per gram of initial Total COD, was 0.37 g/g, highlighting the significant potential of PBM extract with high COD levels and low sugar content for fermentation processes. Additionally, an investigation was carried out to assess the impact of inoculation method, culture adaptation, COD/N ratio, and pH control on fungal biomass growth during cultivation. The results of optimal conditions with response of fungal biomass growth showed production of 0.44, 0.45, and 0.49 g of fungal biomass per gram of initial total COD, with protein contents of 20.2%, 27.1%, and 18.6%, respectively, leading to improved fungal biomass yield. The resulting protein-rich fungal biomass with a focus on the biorefinery platform to complete the value-added cycle, holds promise for applications in various sectors including food, animal feed, biochemical, and biomaterial industries.

Extrusion pre-treatment of cowpea (Vigna unguiculata (L.) Walp.) lignocellulosic sidestream to produce cellulose fibres

BACKGROUND

Various agricultural sidestreams have been demonstrated as feedstock to produce cellulose. To the best of our knowledge, there is no research work on the potential of agricultural sidestream from cowpea (Vigna unguiculata (L.) Walp.), a neglected and underutilised crop to produce cellulose fibres. Conventional methods to produce cellulose consume large amounts of chemicals (NaOH) and produce a high amount of effluent waste. Herein, we investigated extrusion pre-treatment without and with an alkali followed by bleaching as an alternative method to conventional alkaline pre-treatment followed by bleaching to produce cellulose fibres from cowpea sidestream.

RESULTS

Cellulose extracted by extrusion without and with mild alkali followed by bleaching consumed about 20 times less NaOH compared to the conventional method and produced less effluent waste. Extrusion with mild alkali followed by bleaching resulted in higher cellulose yield, purity, and crystallinity compared to extrusion without an alkali followed by bleaching. However, the conventional method resulted in higher cellulose yield, purity and crystallinity compared to extrusion pre-treatment followed by bleaching. Scanning electron microscopy revealed that micro-sized cellulose fibres with an average diameter of 10-15 μm were extracted using both methods. Notably, cellulose fibres extracted using extrusion pre-treatment were shorter than those extracted using the conventional method.

CONCLUSION

Extrusion pre-treatment is a promising continuous alternative to alkaline pre-treatment to produce micro-sized cellulose fibres from low-value, underutilised cowpea lignocellulosic sidestream, for potential use as a filler in composite plastics. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Maleic Acid-Butanol Pretreatment to Enhance Cellulose Accessibility for Enzymatic Hydrolysis and Ethanol Production from Oil Palm Empty Fruit Bunch

Pretreatment of lignocellulosic biomass is crucial yet challenging for sustainable energy production. This study focuses on enhancing enzymatic accessibility of cellulose in oil palm empty fruit bunches by optimizing pretreatment parameters to improve glucose and ethanol yields while reducing fermentation inhibitors. It evaluates the impact of maleic acid concentrations on biorefinery processes. High maleic acid concentrations (>25% w/w) may allow reuse and offer benefits over lower concentrations, such as enhanced delignification and increased sugar yield under milder conditions. Biomass undergoes pretreatment, enzymatic saccharification, and fermentation using Saccharomyces cerevisiae F118. Pretreatment with 75% maleic acid (w/w) for 60 min at 180 °C effectively removes lignin and hemicellulose, increasing cellulose accessibility but results in 74.8% crystallinity, hindering saccharification. A 50% maleic acid pretreatment yielded higher glucose (77.1%). Optimal ethanol production is achieved with 1% maleic acid pretreatment. However, the ethanol yield is negatively impacted by residual maleic acid on the solid matrix.

Biochar filtration of drug-resistant bacteria and active pharmaceutical ingredients to combat antimicrobial resistance

Antimicrobial resistance (AMR) is a major cause of death worldwide, with 1.27 M direct deaths from bacterial drug-resistant infections as of 2019. Dissemination of multidrug-resistant (MDR) bacteria in the environment, in conjunction with pharmapollution by active pharmaceutical ingredients (APIs), create and foster an environmental reservoir of AMR. Creative solutions are required to mitigate environmental AMR, while taking into consideration other aspects of the planetary "Triple Crisis" of pollution, biodiversity loss, and climate change. Waste lignocellulosic biomass (LCB), a byproduct of agriculture and forestry, is the largest stream of non-edible biomass globally. Through pyrolysis, waste LCB can be converted into biochars, which have excellent attributes for adsorption of pollutants-though no studies have yet reliably correlated production conditions with efficacy, nor considered adsorption of human pathogens. By leveraging a bespoke pyrolysis reactor with precisely controlled parameters, we show that production conditions substantially affect sequestration of clinical bacterial isolates, removing up to 94% of Pseudomonas aeruginosa RP73 and 85% of Staphylococcus aureus EMRSA-15. In addition, we show that chars produced at higher peak pyrolysis temperatures (450 °C) can remove up to 88% of the antibiotic clarithromycin from wastewater, as well as significant proportions of many other APIs with varied physicochemical characteristics. These findings provide a first-in-kind insight into how production conditions affect the ability of biochars to mitigate environmental AMR.

Sustainable Films Derived from Eucalyptus spp. Bark: Improving Properties Through Chemical and Physical Pretreatments

This study investigates the sustainable use of Eucalyptus spp. bark through different chemical (hydrothermal, acid, alkaline, and bleaching) and physical (milling) pretreatments in the production of sustainable films. Valorization of agro-industrial residues and the demand for sustainable materials pose challenges for environmentally responsible solutions. Eucalyptus spp. bark, rich in cellulose, hemicellulose, and lignin, is a promising source for creating sustainable materials like films. In this study, the use of chemical and physical treatments aims to optimize biomass extraction and improve the chemical, thermal, mechanical, and optical properties of the films. The films showed an excellent light barrier capacity, with a transmittance below 1%. Crystallinity indices varied with the pretreatment: 8.15% for hydrothermal, 7.01% for alkaline, 7.63% for acid, and 10.80% for bleaching. The highest crystallinity value was obtained through bleaching, by removing amorphous components like lignin and hemicellulose. The alkaline pretreatment yielded stronger films (maximum stress of 8.8 MPa, Young's modulus of 331.3 MPa) owing to the retained lignin and the hemicellulose reinforcing the material. This study contributes to the field of sustainable development by converting residues into valuable materials and by advancing the circular economy. The films' specific properties make them suitable for applications like sustainable packaging, addressing environmental and industrial challenges.

Synthetic biology approaches to improve tolerance of inhibitors in lignocellulosic hydrolysates

Increasing attention is being focused on using lignocellulose for valuable products. Microbial decomposition can convert lignocellulose into renewable biofuels and other high-value bioproducts, contributing to sustainable development. However, the presence of inhibitors in lignocellulosic hydrolysates can negatively affect microorganisms during fermentation. Improving microbial tolerance to these hydrolysates is a major focus in metabolic engineering. Traditional detoxification methods increase costs, so there is a need for cheap and efficient cell-based detoxification strategies. Synthetic biology approaches offer several strategies for improving microbial tolerance, including redox balancing, membrane engineering, omics-guided technologies, expression of protectants and transcription factors, irrational engineering, cell flocculation, and other novel technologies. Advances in molecular biology, high-throughput sequencing, and artificial intelligence (AI) allow for precise strain modification and efficient industrial production. Developing AI-based computational models to guide synthetic biology efforts and creating large-scale heterologous libraries with automation and high-throughput technologies will be important for future research.

A carboxymethyl cellulase from the yeast Cryptococcus gattii WM276: Expression, purification and characterisation

Cryptococcus gattii and its medical implications have been extensively studied. There is, however, a significant knowledge gap regarding cryptococcal survival in its environmental niche, namely woody material, which is glaring given that infection is linked to environmental populations. A gene from C. gattii (WM276), the predominant global molecular type (VGI), has been sequenced and annotated as a putative cellulase. It is therefore, of both medical and industrial intertest to delineate the structure and function of this enzyme. A homology model of the enzyme was constructed as a fusion protein to a maltose binding protein (MBP). The CGB_E4160W gene was overexpressed as an MBP fusion enzyme in Escherichia coli T7 cells and purified to homogeneity using amylose affinity chromatography. The structural and functional character of the enzyme was investigated using fluorescence spectroscopy and enzyme activity assays, respectively. The optimal enzyme pH and temperature were found to be 6.0 and 50 °C, respectively, with an optimal salt concentration of 500 mM. Secondary structure analysis using Far-UV CD reveals that the MBP fusion protein is primarily α-helical with some β-sheets. Intrinsic tryptophan fluorescence illustrates that the MBP-cellulase undergoes a conformational change in the presence of its substrate, CMC-Na+. The thermotolerant and halotolerant nature of this particular cellulase, makes it useful for industrial applications, and adds to our understanding of the pathogen's environmental physiology.

Screening, characterization, and optimization of the fermentation conditions of a novel cellulase-producing microorganism from soil of Qinghai-Tibet Plateau

Cellulases play an important role in the bioconversion of lignocellulose. Microorganisms found in extreme environments are a potentially rich source of cellulases with unique properties. Due to the uniqueness of the environment, the abundant microbial resources in the Qinghai-Tibet Plateau (QTP) are worth being explored. The aim of this study was to isolate and characterize an acidic, mesophilic cellulase-producing microorganism from QTP. Moreover, the fermentation conditions for cellulase production were optimized for future application of cellulase in the development of lignocellulose biomass. A novel cellulase-producing strain, Penicillium oxalicum XC10, was isolated from the soil of QTP. The cellulase produced by XC10 was a mesophilic cellulase that exhibited good acid resistance and some cold-adaptation properties, with maximum activity at pH 4.0 and 40°C. Cellulase activity was significantly enhanced by Na+ (p < 0.05) and inhibited by Mg2+, Ca2+, Cu2+, and Fe3+ (p < 0.05). After optimization, maximum cellulase activity (8.56 U/mL) was increased nearly 10-fold. Optimal fermentation conditions included an inoculum size of 3% (v/v) in a mixture of corn straw (40 g/L), peptone (5 g/L), and Mg2+ (4 g/L), at pH 4.0, 33°C, and shaking at 200 rpm. The specific properties of the P. oxalicum XC10 cellulase suggest the enzyme may serve as an excellent candidate for the bioconversion and utilization of lignocellulose biomass generated as agricultural and food-processing wastes.

Paradigm of engineering recalcitrant non-model microorganism with dominant metabolic pathway as a biorefinery chassis

The development and implementation of microbial chassis cells have profound impacts on circular economy. Non-model bacterium Zymomonas mobilis is an excellent chassis owing to its extraordinary industrial characteristics. Here, the genome-scale metabolic model iZM516 is improved and updated by integrating enzyme constraints to simulate the dynamics of flux distribution and guide pathway design. We show that the innate dominant ethanol pathway of Z. mobilis restricts the titer and rate of these biochemicals. A dominant-metabolism compromised intermediate-chassis (DMCI) strategy is then developed through introducing low toxicity but cofactor imbalanced 2,3-butanediol pathway, and a recombinant D-lactate producer is constructed to produce more than 140.92 g/L and 104.6 g/L D-lactate (yield > 0.97 g/g) from glucose and corncob residue hydrolysate, respectively. Additionally, techno-economic analysis (TEA) and life cycle assessment (LCA) demonstrate the commercialization feasibility and greenhouse gas reduction capability of lignocellulosic D-lactate. This work thus establishes a paradigm for engineering recalcitrant microorganisms as biorefinery chassis.

Soudagar ME, Kalam MA. Lignocellulosic fiber reinforcement in PPRC composites: An analysis of structural and thermal enhancements

This study investigates the fabrication process of biocomposites and their resultant mechanical and thermal properties, essential for evaluating the performance of finished products. Polypropylene random copolymer (PPRC) was employed as the matrix phase, while rice husk (RH), a biowaste filler, was incorporated in varying concentrations. The rice husk fiber was treated with alkali (RHT) to enhance its lignocellulosic content. To improve interfacial bonding, maleic anhydride and NaOH treatment were utilized. Glass fiber grafted on polypropylene (PPGF) and talc powder functioned as additives. Both raw and treated rice husk fibers were characterized using Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), and analytical methods to quantify the composition of lignin, cellulose, hemicellulose, and ash. Significant structural changes were observed, with cellulose content increasing from 26% to 53%. Wood polymer composites (WPC) produced from raw and treated rice husk were evaluated based on morphological studies, Izod impact testing, water absorption, heat distortion temperature (HDT), and VICAT softening temperature (VST). The results demonstrated that the HDT and VST of WPC improved by 24% and 7%, respectively, compared to PPRC, indicating enhanced structural and thermal properties. Additionally, impact strength and water absorption were found to be dependent on cellulose concentrations in the biocomposite. This study underscores the environmental benefits of utilizing biowaste rice husk in biocomposites, promoting sustainability by converting agricultural waste into valuable materials with enhanced properties for various industrial applications.

Enhancing thermophilic methane production from oil palm empty fruit bunches through various pretreatment methods: A comparative study

This study investigated the effects of various pretreatment methods on the anaerobic digestibility of oil palm empty fruit bunches (EFB) for methane production. Pretreatment methods included weak alkaline (2 % Ca(OH)2), weak acid (2 % acetic acid), acidified palm oil mill effluent (POME), biogas effluent, hydrothermal (180 °C, 190 °C, and 200 °C), and microwave pretreatments. All pretreatment methods enhanced methane yield compared to untreated EFB (189.45 mL-CH4/g-VS), with weak alkaline pretreatment being the most effective (277.11 mL-CH4/g-VS), followed by hydrothermal pretreatment at 180 °C (244.33 mL-CH4/g-VS) and biogas effluent pretreatment (238.32 mL-CH4/g-VS). The enhanced methane yield was attributed to increased cellulose content (45.5 % for weak alkaline pretreatment), reduced hemicellulose (18.0 % for hydrothermal pretreatment at 200 °C), and lignin contents (19.0 % for hydrothermal pretreatment at 200 °C), decreased crystallinity index (40.0 % for hydrothermal pretreatment at 200 °C), and increased surface area. Weak alkaline pretreatment also showed the highest net energy balance (8.73 kJ/g-VS) and a short break-even point (2 years). Microbial community analysis revealed that weak alkaline pretreatment favored the growth of syntrophic acetate-oxidizing bacteria and hydrogenotrophic methanogens, contributing to improved methane yield. This study demonstrates the potential of EFB pretreatment, particularly weak alkaline and biogas effluent pretreatment, for enhancing methane production and sustainable management of palm oil mill waste.

Lignin: An Adaptable Biodegradable Polymer Used in Different Formulation Processes

INTRODUCTION

LIG is a biopolymer found in vascular plant cell walls that is created by networks of hydroxylated and methoxylated phenylpropane that are randomly crosslinked. Plant cell walls contain LIG, a biopolymer with significant potential for usage in modern industrial and pharmaceutical applications. It is a renewable raw resource. The plant is mechanically protected by this substance, which may increase its durability. Because it has antibacterial and antioxidant qualities, LIG also shields plants from biological and chemical challenges from the outside world. Researchers have done a great deal of work to create new materials and substances based on LIG. Numerous applications, including those involving antibacterial agents, antioxidant additives, UV protection agents, hydrogel-forming molecules, nanoparticles, and solid dosage forms, have been made with this biopolymer.

METHODS

For this review, a consistent literature screening using the Pubmed database from 2019-2024 has been performed.

RESULTS

The results showed that there is an increase in interest in lignin as an adaptable biomolecule. The most recent studies are focused on the biosynthesis and antimicrobial properties of lignin-derived molecules. Also, the use of lignin in conjunction with nanostructures is actively explored.

CONCLUSIONS

Overall, lignin is a versatile molecule with multiple uses in industry and medical science.

Enzymatic approaches for diversifying bioproducts from cellulosic biomass

Cellulosic biomass is the most abundantly available natural carbon-based renewable resource on Earth. Its widespread availability, combined with rising awareness, evolving policies, and changing regulations supporting sustainable practices, has propelled its role as a crucial renewable feedstock to meet the escalating demand for eco-friendly and renewable materials, chemicals, and fuels. Initially, biorefinery models using cellulosic biomass had focused on single-product platform, primarily monomeric sugars for biofuel. However, since the launch of the first pioneering cellulosic plants in 2014, these models have undergone significant revisions to adapt their biomass upgrading strategy. These changes aim to diversify the bioproduct portfolio and improve the revenue streams of cellulosic biomass biorefineries. Within this area of research and development, enzyme-based technologies can play a significant role by contributing to eco-design in producing and creating innovative bioproducts. This Feature Article highlights our strategies and recent progress in utilizing the biological diversity and inherent selectivity of enzymes to develop and continuously optimize sustainable enzyme-based technologies with distinct application approaches. We have advanced technologies for standalone platforms, which produce various forms of cellulose nanomaterials engineered with customized and enhanced properties and high yields. Additionally, we have tailored technologies for integration within a biorefinery concept. This biorefinery approach prioritizes designing tailored processes to establish bionanomaterials, such as cellulose and lignin nanoparticles, and bioactive molecules as part of a new multi-bioproduct platform for cellulosic biomass biorefineries. These innovations expand the range of bioproducts that can be produced from cellulosic biomass, transcending the conventional focus on monomeric sugars for biofuel production to include biomaterials biorefinery. This shift thereby contributes to strengthening the Bioeconomy strategy and supporting the achievement of several Sustainable Development Goals (SDGs) of the 2030 Agenda for Sustainable Development.

Recent developments on sustainable biobutanol production: a novel integrative review

Renewable and sustainable biofuel production, such as biobutanol, is becoming increasingly popular as a substitute for non-renewable and depleted petrol fuel. Many researchers have studied how to produce butanol cheaply by considering appropriate feedstock materials and bioprocess technologies. The production of biobutanol through acetone-butanol-ethanol (ABE) is highly sought after around the world because of its sustainable supply and lack of competition with food. The purpose of this study is to present the current biobutanol production research and to analyse the biobutanol research conducted during 2006 to 2023. The keyword used in this study is "Biobutanol," and the relevant data was extracted from the Web of Science database (WoS). According to the results, institutions and scholars from the People's Republic of China, the USA, and India have the highest number of cited papers across a broad spectrum of topics including acetone-butanol-ethanol (ABE) fermentation, biobutanol, various pretreatment techniques, and pervaporation. The success of biobutanol fermentation from biomass depends on the ability of the fermentation operation to match the microbial behaviour along with the appropriate bioprocessing strategies to improve the entire process to be suitable for industrial scale. Based on the review data, we will look at the biobutanol technologies and appropriate strategies that have been developed to improve biobutanol production from renewable biomass.

Extraction and improvement of protein functionality using steam explosion pretreatment: advances, challenges, and perspectives

Protein has become an increasingly valuable food component with high global demand. Consequently, unconventional sources, such as industrial and agroindustrial wastes and by-products, emerge as interesting alternatives to meet this demand, considering the UN Sustainable Development Goals and the transition to a circular economy. In this context, this work presents a review of the use of Steam Explosion (SE), a green technique that can be employed as a pretreatment for various waste materials, including bones, hide/leather, feathers, and wool, aimming the extraction of protein compounds, such as low molecular weight biopeptides, gelatin, and keratin, as well as to enhance the protein functionality of grains and meals. The SE technique and the main factors affecting the process's efficiency were detailed. Promising experimental studies are discussed, along with the mechanisms responsible for protein extraction and functionality improvement, as well as the main reported and suggested applications. In general, steam explosion favored yields in subsequent extraction processes, ranging from 27 to 95%, in addition to enhancing solubility and functional protein properties. Nonetheless, it is crucial to maintain the continuity of research on this topic to drive advancements in ensuring the safety of the extracted compounds for use in consumable products and oral ingestion.

Enabling Lignin Valorization Through Integrated Advances in Plant Biology and Biorefining

Despite lignin having long been viewed as an impediment to the processing of biomass for the production of paper, biofuels, and high-value chemicals, the valorization of lignin to fuels, chemicals, and materials is now clearly recognized as a critical element for the lignocellulosic bioeconomy. However, the intended application for lignin will likely require a preferred lignin composition and form. To that end, effective lignin valorization will require the integration of plant biology, providing optimal feedstocks, with chemical process engineering, providing efficient lignin transformations. Recent advances in our understanding of lignin biosynthesis have shown that lignin structure is extremely diverse and potentially tunable, while simultaneous developments in lignin refining have resulted in the development of several processes that are more agnostic to lignin composition. Here, we review the interface between in planta lignin design and lignin processing and discuss the advances necessary for lignin valorization to become a feature of advanced biorefining.

Biocalorimetry-aided monitoring of fungal pretreatment of lignocellulosic agricultural residues

The present study aimed to investigate whether and how non-invasive biocalorimetric measurements could serve for process monitoring of fungal pretreatment during solid-state fermentation (SSF) of lignocellulosic agricultural residues such as wheat straw. Seven filamentous fungi representing different lignocellulose decay types were employed. Water-soluble sugars being immediately available after fungal pretreatment and those becoming water-extractable after enzymatic digestion of pretreated wheat straw with hydrolysing (hemi)cellulases were considered to constitute the total bioaccessible sugar fraction. The latter was used to indicate the success of pretreatments and linked to corresponding species-specific metabolic heat yield coefficients (YQ/X) derived from metabolic heat flux measurements during fungal wheat straw colonisation. An YQ/X range of about 120 to 140 kJ/g was seemingly optimal for pretreatment upon consideration of all investigated fungi and application of a non-linear Gaussian fitting model. Upon exclusion from analysis of the brown-rot basidiomycete Gloeophyllum trabeum, which differs from all other here investigated fungi in employing extracellular Fenton chemistry for lignocellulose decomposition, a linear relationship where amounts of total bioaccessible sugars were suggested to increase with increasing YQ/X values was obtained. It remains to be elucidated whether an YQ/X range being optimal for fungal pretreatment could firmly be established, or if the sugar accessibility for post-treatment generally increases with increasing YQ/X values as long as "conventional" enzymatic, i.e. (hemi)cellulase-based, lignocellulose decomposition mechanisms are operative. In any case, metabolic heat measurement-derived parameters such as YQ/X values may become very valuable tools supporting the assessment of the suitability of different fungal species for pretreatment of lignocellulosic substrates. KEY POINTS: • Biocalorimetry was used to monitor wheat straw pretreatment with seven filamentous fungi. • Metabolic heat yield coefficients (YQ/X) seem to indicate pretreatment success. • YQ/X values may support the selection of suitable fungal strains for pretreatment.

Enhancing anaerobic digestion of lignocellulosic biomass by mechanical cotreatment

BACKGROUND

The aim of this study was to increase the accessibility and accelerate the breakdown of lignocellulosic biomass to methane in an anaerobic fermentation system by mechanical cotreatment: milling during fermentation, as an alternative to conventional pretreatment prior to biological deconstruction. Effluent from a mesophilic anaerobic digester running with unpretreated senescent switchgrass as the predominant carbon source was collected and subjected to ball milling for 0.5, 2, 5 and 10 min. Following this, a batch fermentation test was conducted with this material in triplicate for an additional 18 days with unmilled effluent as the 'status quo' control.

RESULTS

The results indicate 0.5 - 10 min of cotreatment increased sugar solubilization by 5- 13% when compared to the unmilled control, with greater solubilization correlated with increased milling duration. Biogas concentrations ranged from 44% to 55.5% methane with the balance carbon dioxide. The total biogas production was statistically higher than the unmilled control for all treatments with 2 or more minutes of milling (α = 0.1). Cotreatment also decreased mean particle size. Energy consumption measurements of a lab-scale mill indicate that longer durations of milling offer diminishing benefits with respect to additional methane production.

CONCLUSIONS

Cotreatment in anaerobic digestion systems, as demonstrated in this study, provides an alternative approach to conventional pretreatments to increase biogas production from lignocellulosic grassy material.

Potential of Plantain Pseudostems (Musa AAB Simmonds) for Developing Biobased Composite Materials

A plantain pseudostem was harvested and processed on the same day. The process began with manually separating the sheaths (80.85%) and the core (19.14%). The sheaths were subjected to a mechanical shredding process using paddles, extracting 2.20% of lignocellulosic fibers and 2.12% of sap, compared to the fresh weight of the sheaths. The fibers were washed, dried, combed, and spun in their native state and subjected to a steam explosion treatment, while the sap was subjected to filtration and evaporation. In the case of the core, it was subjected to manual cutting, drying, grinding, and sieving to separate 12.81% of the starch and 6.39% of the short lignocellulosic fibers, compared to the fresh weight of the core. The surface modification method using steam explosion succeeded in removing a low proportion of hemicellulose and lignin in the fibers coming from the shims, according to what was shown by Fourier Transform Infrared Spectroscopy (FT-IR), Thermogravimetric Analysis (TGA), and Differential Scanning Calorimetry (DSC), achieving increased σmax and ε from the tensile test and greater thermal stability compared to its native state. The sap presented hygroscopic behavior by FT-IR and the highest thermal stability from TGA, while the starch from the core presented the lowest hygroscopic character and thermal stability. Although the pseudostem supplied two types of fibers, lower lignin content was identified in those from the core. Finally, the yarns were elaborated by using the fibers of the sheaths in their native and steam-exploded states, identifying differences in the processing and their respective physical and mechanical properties.

Dilute gluconic acid pretreatment and fermentation of wheat straw to ethanol

Gluconic acid's potential as a wheat straw pretreatment agent was studied at different concentrations (0.125-1 M) and temperatures (160-190 °C) for 30 min, followed by enzymatic hydrolysis. 0.125 M gluconic acid, 170 °C, yielded the highest xylose output, while 0.5 M gluconic acid at 190 °C yielded the best glucose yield. A fraction of gluconic acid decomposed during pretreatment. Detoxified hemicellulose hydrolysate from 0.125 M gluconate at 170 °C for 60 min showed promise for ethanol production. The gluconate contained in the detoxified hemicellulose hydrolysate can be fermented to ethanol along with other hemicellulose sugars present by Escherichia coli SL100. The ethanol yield from gluconate and sugars was about 90.4 ± 1.8%. The pretreated solids can be effectively converted to ethanol by Saccharomyces cerevisiae D5A via simultaneous saccharification and fermentation with the cellulase and β-glucosidase addition. The ethanol yield achieved was 92.8 ± 2.0% of the theoretical maximum. The cellulose conversion was about 70.8 ± 0.8%.

PP/Jute Fiber Composites: Effect of Biological Route of Surface Treatment and Content of Jute on Composites

Jute as a fiber has many applications. It is also used in polymers as reinforcement due to its good tensile properties. However, when it is used in polymer matrices, there is a lack of adhesion between the polymer and jute fiber. Surface treatment of fiber using chemicals has been found to improve the properties. However, the use of chemicals causes environmental pollution, when these chemicals are discharged into the environment. In this paper, an attempt has been made to study the effect of the biological route to surface treat the jute fiber. The effect of surface treatment on the morphology of jute was examined. A comparative study was on the crystalline, thermal, and tensile fracture morphology of the composites to understand the effect of the incorporation of untreated and treated jute fibers in polypropylene (PP).

Scale-up of microbial lipid and bioethanol production from oilcane

Microbial oils are a sustainable biomass-derived substitute for liquid fuels and vegetable oils. Oilcane, an engineered sugarcane with superior feedstock characteristics for biodiesel production, is a promising candidate for bioconversion. This study describes the processing of oilcane stems into juice and hydrothermally pretreated lignocellulosic hydrolysate and their valorization to ethanol and microbial oil using Saccharomyces cerevisiae and engineered Rhodosporidium toruloides strains, respectively. A bioethanol titer of 106 g/L was obtained from S. cerevisiae grown on oilcane juice in a 3 L fermenter, and a lipid titer of 8.8 g/L was obtained from R. toruloides grown on oilcane hydrolysate in a 75 L fermenter. Oil was extracted from the R. toruloides cells using supercritical CO2, and the observed fatty acid profile was consistent with previous studies on this strain. These results demonstrate the feasibility of pilot-scale lipid production from oilcane hydrolysate as part of an integrated bioconversion strategy.

Enhanced crystalline cellulose degradation by a novel metagenome-derived cellulase enzyme

Metagenomics has revolutionized access to genomic information of microorganisms inhabiting the gut of herbivorous animals, circumventing the need for their isolation and cultivation. Exploring these microorganisms for novel hydrolytic enzymes becomes unattainable without utilizing metagenome sequencing. In this study, we harnessed a suite of bioinformatic analyses to discover a novel cellulase-degrading enzyme from the camel rumen metagenome. Among the protein-coding sequences containing cellulase-encoding domains, we identified and subsequently cloned and purified a promising candidate cellulase enzyme, Celcm05-2, to a state of homogeneity. The enzyme belonged to GH5 subfamily 4 and exhibited robust enzymatic activity under acidic pH conditions. It maintained hydrolytic activity under various environmental conditions, including the presence of metal ions, non-ionic surfactant Triton X-100, organic solvents, and varying temperatures. With an optimal temperature of 40 °C, Celcm05-2 showcased remarkable efficiency when deployed on crystalline cellulose (> 3.6 IU/mL), specifically Avicel, thereby positioning it as an attractive candidate for a myriad of biotechnological applications spanning biofuel production, paper and pulp processing, and textile manufacturing. Efficient biodegradation of waste paper pulp residues and the evidence of biopolishing suggested that Celcm05-2 can be used in the bioprocessing of cellulosic craft fabrics in the textile industry. Our findings suggest that the camel rumen microbiome can be mined for novel cellulase enzymes that can find potential applications across diverse biotechnological processes.

Structural and functional analysis of the active cow rumen's microbial community provides a catalogue of genes and microbes participating in the deconstruction of cardoon biomass

BACKGROUND

Ruminal microbial communities enriched on lignocellulosic biomass have shown considerable promise for the discovery of microorganisms and enzymes involved in digesting cell wall compounds, a key bottleneck in the development of second-generation biofuels and bioproducts, enabling a circular bioeconomy. Cardoon (Cynara cardunculus) is a promising inedible energy crop for current and future cellulosic biorefineries and the emerging bioenergy and bioproducts industries. The rumen microbiome can be considered an anaerobic "bioreactor", where the resident microbiota carry out the depolymerization and hydrolysis of plant cell wall polysaccharides (PCWPs) through the catalytic action of fibrolytic enzymes. In this context, the rumen microbiota represents a potential source of microbes and fibrolytic enzymes suitable for biofuel production from feedstocks. In this study, metatranscriptomic and 16S rRNA sequencing were used to profile the microbiome and to investigate the genetic features within the microbial community adherent to the fiber fractions of the rumen content and to the residue of cardoon biomass incubated in the rumen of cannulated cows.

RESULTS

The metatranscriptome of the cardoon and rumen fibre-adherent microbial communities were dissected in their functional and taxonomic components. From a functional point of view, transcripts involved in the methanogenesis from CO2 and H2, and from methanol were over-represented in the cardoon-adherent microbial community and were affiliated with the Methanobrevibacter and Methanosphaera of the Euryarchaeota phylum. Transcripts encoding glycoside hydrolases (GHs), carbohydrate-binding modules (CBMs), carbohydrate esterases (CEs), polysaccharide lyases (PLs), and glycoside transferases (GTs) accounted for 1.5% (6,957) of the total RNA coding transcripts and were taxonomically affiliated to major rumen fibrolytic microbes, such as Oscillospiraceae, Fibrobacteraceae, Neocallimastigaceae, Prevotellaceae, Lachnospiraceae, and Treponemataceae. The comparison of the expression profile between cardoon and rumen fiber-adherent microbial communities highlighted that specific fibrolytic enzymes were potentially responsible for the breakdown of cardoon PCWPs, which was driven by specific taxa, mainly Ruminococcus, Treponema, and Neocallimastigaceae.

CONCLUSIONS

Analysis of 16S rRNA and metatranscriptomic sequencing data revealed that the cow rumen microbiome harbors a repertoire of new enzymes capable of degrading PCWPs. Our results demonstrate the feasibility of using metatranscriptomics of enriched microbial RNA as a potential approach for accelerating the discovery of novel cellulolytic enzymes that could be harnessed for biotechnology. This research contributes a relevant perspective towards degrading cellulosic biomass and providing an economical route to the production of advanced biofuels and high-value bioproducts.

Renewable Energy Potential: Second-Generation Biomass as Feedstock for Bioethanol Production

Biofuels are clean and renewable energy resources gaining increased attention as a potential replacement for non-renewable petroleum-based fuels. They are derived from biomass that could either be animal-based or belong to any of the three generations of plant biomass (agricultural crops, lignocellulosic materials, or algae). Over 130 studies including experimental research, case studies, literature reviews, and website publications related to bioethanol production were evaluated; different methods and techniques have been tested by scientists and researchers in this field, and the most optimal conditions have been adopted for the generation of biofuels from biomass. This has ultimately led to a subsequent scale-up of procedures and the establishment of pilot, demo, and large-scale plants/biorefineries in some regions of the world. Nevertheless, there are still challenges associated with the production of bioethanol from lignocellulosic biomass, such as recalcitrance of the cell wall, multiple pretreatment steps, prolonged hydrolysis time, degradation product formation, cost, etc., which have impeded the implementation of its large-scale production, which needs to be addressed. This review gives an overview of biomass and bioenergy, the structure and composition of lignocellulosic biomass, biofuel classification, bioethanol as an energy source, bioethanol production processes, different pretreatment and hydrolysis techniques, inhibitory product formation, fermentation strategies/process, the microorganisms used for fermentation, distillation, legislation in support of advanced biofuel, and industrial projects on advanced bioethanol. The ultimate objective is still to find the best conditions and technology possible to sustainably and inexpensively produce a high bioethanol yield.

Valorization of crop residues and animal wastes: Anaerobic co-digestion technology

To switch the over-reliance on fossil-based resources, curb environmental quality deterioration, and promote the use of renewable fuels, much attention has recently been directed toward the implementation of sustainable and environmentally benign 'waste-to-energy' technology exploiting a clean, inexhaustible, carbon-neutral, and renewable energy source, namely agricultural biomass. From this perspective, anaerobic co-digestion (AcoD) technology emerges as a potent and plausible approach to attain sustainable energy development, foster environmental sustainability, and, most importantly, circumvent the key challenges associated with mono-digestion. This review article provides a comprehensive overview of AcoD as a biochemical valorization pathway of crop residues and livestock manure for biogas production. Furthermore, this manuscript aims to assess the different biotic and abiotic parameters affecting co-digestion efficiency and present recent advancements in pretreatment technologies designed to enhance feedstock biodegradability and conversion rate. It can be concluded that the substantial quantities of crop residues and animal waste generated annually from agricultural practices represent valuable bioenergy resources that can contribute to meeting global targets for affordable renewable energy. Nevertheless, extensive and multidisciplinary research is needed to evolve the industrial-scale implementation of AcoD technology of livestock waste and crop residues, particularly when a pretreatment phase is included, and bridge the gap between small-scale studies and real-world applications.

Lignin reduction in sugarcane by performing CRISPR/Cas9 site-direct mutation of SoLIM transcription factor

Genetic engineering of plant cell walls is limited for reducing lignocellulose recalcitrance, so mild and/or green-like pretreatment is still required for sequential enzymatic saccharification. Here, we report a method to reduce lignin content in sugarcane stalks using the CRISPR/Cas 9 technique. Three target sequences of SoLIM were designed and fused to pRGEB32. The cassette constructs were introduced into sugarcane calli cv. KK3 through Agrobacterium-mediated transformation. We produced one base substitution and one insertion line for the 1st target site; two insertions, one deletion, and one base substitution for the 2nd target site; and one base substitution and insertion for the 3rd target site. qRT-PCR analysis of SoLIM, SoPAL, SoC4H, and SoCAD showeded that downregulation of SoLIM by single nucleotide insertions or deletions reduced the expression of SoPAL, SoC4H, and SoCAD. Consequently, the edited lines contained 9.74 to 51.46% less lignin content compared to that in the wild-type plants. The syringyl/guaiacyl (S/G) ratio of the edited lines ranged between 0.23 and 0.49, while the wild-type was 0.22. The histochemical evaluation and scanning electron microscopy of the cell walls supported this observation. A low lignin content sugarcane will provide a better feedstock for second-generation bioethanol production.

Preparation and research progress of lignin-based supercapacitor electrode materials

The reserve of lignin in the biological world is the second largest biomass resource after cellulose. Lignin has the characteristics of wide sources, low cost, and rich active components. Due to environmental pollution and energy scarcity, lignin is often used as a substitute good for petrochemical products. Lignin-based functional materials can be prepared by chemical modification or compounding, which are widely used in the fields of energy storage, chemical industry, and medicine. Among them, lignin-based carbon materials have the features of stable chemical properties, large pH application range, ideal electrical conductivity, developed pore size, and high specific surface area, which have great application prospects as supercapacitor materials. This paper mainly introduces the structural properties of lignin, the methods, and mechanisms of carbonization, pore-making, and pore-expansion, as well as the research progress of lignin-based carbon materials for supercapacitors, while looking forward to the future research direction of lignin carbon materials.

Detoxification of corn stover prehydrolysate by different biochars and its effect on lactic acid fermentation

During the utilization of lignocellulosic biomass such as corn stover, many by-products are produced in the pretreatment process that can severely inhibit the activity of microbes in the fermentation step. To achieve efficient biomass conversion, detoxification is usually required before microbial fermentation. In this study, the prehydrolysate from dilute acid pretreatment of corn stover was used as a lactic acid fermentation substrate. Biochars made from corn stover (CSB), cow manure (CMB), and a mixture of corn stover and cow manure (MB) were applied for the detoxification of the prehydrolysate. All three types of biochar had a porous structure with a specific surface area ranging from 4.08 m2 g-1 (CMB) to 7.03 m2 g-1 (MB). After detoxification, both the numbers of inhibitors and their concentrations in the prehydrolysate decreased, indicating that the biochars prepared in this study were effective in inhibitor removal. The concentration of lactic acid obtained from the prehydrolysate without detoxification was only 12.43 g L-1 after fermentation for 96 h with a productivity of 0.13 g (L h)-1. Although the specific area of CMB was the lowest among the three biochars, the CMB-treated prehydrolysate resulted in the highest lactic acid concentration of 39.25 g L-1 at 96 h with a productivity of 0.41 g (L h)-1. The lactic acid bacteria in the CMB-treated prehydrolysate grew faster than the other two biochars, reaching an OD value of 8.12 at 48 h. The results showed promise for the use of agricultural wastes to make biochar to increase the yield of lactic acid fermentation through the detoxification process.

Corn stover variability drives differences in bisabolene production by engineered Rhodotorula toruloides

Microbial conversion of lignocellulosic biomass represents an alternative route for production of biofuels and bioproducts. While researchers have mostly focused on engineering strains such as Rhodotorula toruloides for better bisabolene production as a sustainable aviation fuel, less is known about the impact of the feedstock heterogeneity on bisabolene production. Critical material attributes like feedstock composition, nutritional content, and inhibitory compounds can all influence bioconversion. Further, the given feedstocks can have a marked influence on selection of suitable pretreatment and hydrolysis technologies, optimizing the fermentation conditions, and possibly even modifying the microorganism's metabolic pathways, to better utilize the available feedstock. This work aimed to examine and understand how variations in corn stover batches, anatomical fractions, and storage conditions impact the efficiency of bisabolene production by R. toruloides. All of these represent different facets of feedstock heterogeneity. Deacetylation, mechanical refining, and enzymatic hydrolysis of these variable feedstocks served as the basis of this research. The resulting hydrolysates were converted to bisabolene via fermentation, a sustainable aviation fuel precursor, using an engineered R. toruloides strain. This study showed that different sources of feedstock heterogeneity can influence microbial growth and product titer in counterintuitive ways, as revealed through global analysis of protein expression. The maximum bisabolene produced by R. toruloides was on the stalk fraction of corn stover hydrolysate (8.89 ± 0.47 g/L). Further, proteomics analysis comparing the protein expression between the anatomic fractions showed that proteins relating to carbohydrate metabolism, energy production, and conversion as well as inorganic ion transport metabolism were either significantly upregulated or downregulated. Specifically, downregulation of proteins related to the iron-sulfur cluster in stalk fraction suggests a coordinated response by R. toruloides to maintain overall metabolic balance, and this was corroborated by the concentration of iron in the feedstocks.

ONE-SENTENCE SUMMARY

This study elucidates the effects of different sources of corn stover on bisabolene production by engineered Rhodotorula toruloides, highlighting the importance of understanding feedstock variability to enhance bioprocess efficiency and economic outcomes.

Tolerance of engineered Rhodosporidium toruloides to sorghum hydrolysates during batch and fed-batch lipid production

BACKGROUND

Oleaginous yeasts are a promising candidate for the sustainable conversion of lignocellulosic feedstocks into fuels and chemicals, but their growth on these substrates can be inhibited as a result of upstream pretreatment and enzymatic hydrolysis conditions. Previous studies indicate a high citrate buffer concentration during hydrolysis inhibits downstream cell growth and ethanol fermentation in Saccharomyces cerevisiae. In this study, an engineered Rhodosporidium toruloides strain with enhanced lipid accumulation was grown on sorghum hydrolysate with high and low citrate buffer concentrations.

RESULTS

Both hydrolysis conditions resulted in similar sugar recovery rates and concentrations. No significant differences in cell growth, sugar utilization rates, or lipid production rates were observed between the two citrate buffer conditions during batch fermentation of R. toruloides. Under fed-batch growth on low-citrate hydrolysate a lipid titer of 16.7 g/L was obtained.

CONCLUSIONS

Citrate buffer was not found to inhibit growth or lipid production in this engineered R. toruloides strain, nor did reducing the citrate buffer concentration negatively affect sugar yields in the hydrolysate. As this process is scaled-up, $131 per ton of hydrothermally pretreated biomass can be saved by use of the lower citrate buffer concentration during enzymatic hydrolysis.

Melt Spinning Process Optimization of Polyethylene Terephthalate Fiber Structure and Properties from Tetron Cotton Knitted Fabric

Polyester/cotton fabrics with different proportions of Tetron Cotton, TC (35% Cotton/65% PET), and Chief Value Cotton, CVC (60% Cotton/40% PET), were investigated by removing the cotton component under various phosphoric acidic conditions including the use of cellulase enzymes. The remaining polyethylene terephthalate (PET) component was spun using the melt spinning method. Only 85% H3PO4-Enz_TC could be spun into consistent filament fibers. The effects of Acid-Enz TC (obtained from a powder preparation of 85% H3PO4-Enz_TC) at different weight amounts (1, 2, 5, and 10 %wt) blending with WF-rPET powder prepared by white recycled polyester fabric were evaluated for fiber spinnability at different winding speeds of 1000 and 1500 m/min. The results revealed that recycled PET fiber spun by adding Acid-Enz_TC up to 10 %wt gave uniformly distributed filament fibers. A comparative study of the physical, thermal, and mechanical properties also investigated the relationship between the effect of Acid-Enz_TC and the structure of the obtained fibers. Acid-Enz_TC:WF-rPET (5:95) was the optimal ratio. The thermal values were analyzed by DSC and TGA and crystallinity was analyzed by XRD, with mechanical strength closed to 100% WF-rPET. The FTIR analysis of the functional groups showed the removal of cotton from the blended fabrics. Other factors such as the Acid-Enz_TC component in WF-rPET, extraction conditions, purity, thermal, chemical, and exposure experiences also affected the formability and properties of recycled PET made from non-single-component raw materials. This study advanced the understanding of recycling PET from TC fabrics by strategically removing cotton from polyester-cotton blends and then recycling using controlled conditions and processes via the melt spinning method.

Cellulase-immobilized chitosan-coated magnetic nanoparticles for saccharification of lignocellulosic biomass

Devising and consolidating cost-effective and greener technologies for sustainable energy production pertain to some of the most pressing needs of the present times. Bioconversion of abundantly available lignocellulosic materials into fermentable sugars to produce biofuels involves the cost-extensive requirement of hydrolytic enzymes called cellulases. Cellulases are highly selective and eco-friendly biocatalysts responsible for deconstruction of complex polysaccharides into simple sugars. Currently, immobilization of cellulases is being carried out on magnetic nanoparticles functionalized with suitable biopolymers such as chitosan. Chitosan, a biocompatible polymer, exhibits high surface area, chemical/thermal stability, functionality, and reusability. The chitosan-functionalized magnetic nanocomposites (Ch-MNCs) present a nanobiocatalytic system that enables easy retrieval, separation, and recycling of cellulases, thereby offering a cost-effective and sustainable approach for biomass hydrolysis. These functional nanostructures show enormous potential owing to certain physicochemical and structural features that have been discussed in a comprehensive manner in this review. It provides an insight into the synthesis, immobilization, and application of cellulase immobilized Ch-MNCs for biomass hydrolysis. This review aims to bridge the gap between sustainable utilization and economic viability of employing replenishable agro-residues for cellulosic ethanol production by incorporating the recently emerging nanocomposite immobilization approach.

Conversion of low-rank coal and sewage sludge into syngas for H2SO4 production and straw hydrolysis

This study investigates the potential of using sewage sludge and low-rank coal for the sustainable production of sulfuric acid, which can then be used for the hydrolysis of straw through ASPEN PLUS simulation. Pyrolysis and gasification processes were used to convert sewage sludge and low-rank coal into syngas, which were then purified and oxidized to produce H2SO4 and NH3 gas. The pyro-gasification enhanced syngas yield. The effects of key process parameters such as temperature, steam-to-biomass ratio, equivalence ratio, and feedstock composition on the yield and composition of syngas and H2SO4 coupled with minor parameters like pressure were investigated. The simulation was conducted over the temperature and pressure range of 400 - 900°°C and 70 - 150 kPa respectively. While the steam-to-biomass ratio and equivalence ratio were respectively varied from 0.66 - 1.65 and 0.14 - 0.35. Part of the 1012.88 kg/h of H2SO4 produced was used to hydrolyze straw, producing glucose as a valuable feedstock for biorefineries. About 3989.10 kg/h of NH3 was produced. Results showed that the use of sewage sludge and low-rank coal as feedstocks for syngas production can be a sustainable and cost-effective alternative to traditional fossil fuels. The resulting H2SO4 can also be used for various other applications, such as in the production of fertilizers and detergents. Overall, this study agrees with the literature, demonstrates the potential of integrating biomass and waste resources for the sustainable production of high-value chemicals and fuels, and contributes to the field of sustainable chemical and energy production while addressing environmental and economic considerations.

Current Status and Challenges for Metal-Organic-Framework-Assisted Conversion of Biomass into Value-Added Chemicals

Owing to the abundance of availability, low cost, and environmental-friendliness, biomass waste could serve as a prospective renewable source for value-added chemicals. Nevertheless, biomass conversion into chemicals is quite challenging due to the heterogeneous nature of biomass waste. Biomass-derived chemicals are appealing sustainable solutions that can reduce the dependency on existing petroleum-based production. Metal-organic frameworks (MOFs)-based catalysts and their composite materials have attracted considerable amounts of interest in biomass conversion applications recently because of their interesting physical and chemical characteristics. Due to their tunability, the catalytic activity and selectivity of MOF-based catalyst/composite materials can be tailored by functionalizing them with a variety of functional groups to enhance biomass conversion efficiency. This review focuses on the catalytic transformation of lignocellulosic biomass into value-added chemicals by employing MOF-based catalyst/composite materials. The main focus is given to the production of the platform chemicals HMF and Furfural from the corresponding (hemi)cellulosic biomass, due to their versatility as intermediates for the production of various biobased chemicals and fuels. The effects of different experimental parameters on the conversion of biomass by MOF-based catalysts are also included. Finally, current challenges and perspectives of biomass conversion into chemicals by MOF-based catalysts are highlighted.

Mechanism of furfural toxicity and metabolic strategies to engineer tolerance in microbial strains

Lignocellulosic biomass represents a carbon neutral cheap and versatile source of carbon which can be converted to biofuels. A pretreatment step is frequently used to make the lignocellulosic carbon bioavailable for microbial metabolism. Dilute acid pretreatment at high temperature and pressure is commonly utilized to efficiently solubilize the pentose fraction by hydrolyzing the hemicellulose fibers and the process results in formation of furans-furfural and 5-hydroxymethyl furfural-and other inhibitors which are detrimental to metabolism. The presence of inhibitors in the medium reduce productivity of microbial biocatalysts and result in increased production costs. Furfural is the key furan inhibitor which acts synergistically along with other inhibitors present in the hydrolysate. In this review, the mode of furfural toxicity on microbial metabolism and metabolic strategies to increase tolerance is discussed. Shared cellular targets between furfural and acetic acid are compared followed by discussing further strategies to engineer tolerance. Finally, the possibility to use furfural as a model inhibitor of dilute acid pretreated lignocellulosic hydrolysate is discussed. The furfural tolerant strains will harbor an efficient lignocellulosic carbon to pyruvate conversion mechanism in presence of stressors in the medium. The pyruvate can be channeled to any metabolite of interest by appropriate modulation of downstream pathway of interest. The aim of this review is to emphasize the use of hydrolysate as a carbon source for bioproduction of biofuels and other compounds of industrial importance.

Quantitative Analysis of The High-Yield Hydrolysis of Kelp by Laminarinase and Alginate Lyase

Kelp is an abundant, farmable biomass-containing laminarin and alginate as major polysaccharides, providing an excellent model substrate to study their deconstruction by simple enzyme mixtures. Our previous study showed strong reactivity of the glycoside hydrolase family 55 during hydrolysis of purified laminarin, raising the question of its reactivity with intact kelp. In this study, we determined that a combination of a single glycoside hydrolase family 55 β-1,3-exoglucanase with a broad-specificity alginate lyase from the polysaccharide lyase family 18 gives efficient hydrolysis of untreated kelp to a mixture of simple sugars, that is, glucose, gentiobiose, mannitol-end glucose, and mannuronic and guluronic acids and their soluble oligomers. Quantitative assignments from nanostructure initiator mass spectrometry (NIMS) and 2D HSQC NMR spectroscopy and analysis of the reaction time-course are provided. The data suggest that binary combinations of enzymes targeted to the unique polysaccharide composition of marine biomass are sufficient to deconstruct kelp into soluble sugars for microbial fermentation.

Sustainable biohydrogen production from lignocellulosic biomass sources - metabolic pathways, production enhancement, and challenges

Hydrogen production from biological processes has been hailed as a promising strategy for generating sustainable energy. Fermentative hydrogen production processes such as dark and photofermentation are considered more sustainable and economical than other biological methods such as biophotolysis. However, these methods have constraints such as low hydrogen yield and conversion efficiency, so practical implementations still need to be made. The present review provides an assessment and feasibility of producing biohydrogen through dark and photofermentation techniques utilizing various lignocellulosic biomass wastes as substrates. Furthermore, this review includes information about the strategies to increase the productivity rate of biohydrogen in an eco-friendly and sustainable manner, like integration of dark and photofermentation techniques, pretreatment of biomass, genetic modification of microorganisms, and application of nanoadditives.