Recent advances in lignocellulosic biomass for biofuels and value-added bioproducts - A critical review

A comprehensive review of sustainable valorisation of lignocellulosic biomass and plastic waste into biofuels and chemicals via co-liquefaction

Liquefaction stands out as a promising strategy within the bioeconomy, offering a pathway to convert waste into valuable fuels and products. However, bio-oil from biomass liquefaction has high oxygen content and poor calorific value, limiting its practical applications. To overcome these challenges, one promising approach is the co-liquefaction of oxygen-rich biomass with hydrogen-rich plastic, offering a sustainable means of producing high-quality oil. This review explores lignocellulosic biomass and plastic co-liquefaction, highlighting its behaviours, reaction pathways, and process parameters' effects. The co-liquefaction process offers significant advantages over lignocellulosic biomass or plastic liquefaction in improving oil quality and yield. Comprehensive studies on the effect of process parameters and reaction pathways are much needed to optimise the conditions and design an efficient and effective co-liquefaction process for lignocellulosic biomass and plastics. Life cycle assessment (LCA) and techno-economic assessment (TEA) are two viable approaches to evaluating the potential environmental impacts and economic performance, respectively. Finally, lignocellulosic biomass and plastic waste co-liquefaction is a viable approach to managing waste and producing valuable materials, which promotes significant values, including resource efficiency, waste reduction, environmental sustainability, and economic opportunities.

Systems Metabolic Engineering of Genome-Reduced Pseudomonas putida for Efficient Production of Polyhydroxyalkanoate from p-Coumaric Acid

Pseudomonas putida KT2440, which harbors native aromatic catabolic pathways, has emerged as a cell factory for funnelling lignin derivatives to medium-chain-length polyhydroxyalkanoates (mcl-PHA). To enhance this bioconversion, we engineered the genome-reduced strain P. putida KTU-U27 (with higher PHA productivity than its parental strain KT2440) to further enhance mcl-PHA synthesis from the lignin-derived aromatic compound p-coumaric acid (p-CA). Three targeted strategies were employed: (i) blocking PHA degradation via deletion of phaZ; (ii) suppressing β-oxidation by deleting fadBA1 and fadBA2; and (iii) enhancing biosynthesis through overexpression of phaC1 and alkK, resulting in the engineered strain KTU-U27ΔZ2BA-P46C1K. Subsequent optimization of the carbon-to-nitrogen (C/N) ratio and high-density fed-batch fermentation further improved PHA productivity. To adapt the substrate toxicity, strain tolerance toward p-CA was augmented by overexpressing the ttg2ABCDE operon and the vacJ gene. Under optimized fed-batch fermentation conditions (initial C/N ratio of 8:4), the final strain KTU-U27ΔZ2BA-P46C1K-P46TJ achieved a cell dry weight of 2050 mg/L with a PHA content of 82.19 wt %, corresponding to a PHA yield of 1685 mg/L, which is the highest reported to date using p-CA as the sole carbon source. This integrated approach of combining genome reduction, metabolic engineering, and bioprocess optimization, provides a scalable platform for mcl-PHA production from lignin-derived aromatics, highlighting the potential of KTU-U27-based chassis for cost-effective lignin valorization.

Near-infrared spectroscopy as a green analytical tool for sustainable biomass characterization for biofuels and bioproducts: An overview

Biomass, a widely used renewable energy source, requires characterization to optimize biofuel and bioproduct processes, customize feedstocks, and ensure economic and environmental sustainability. Conventional wet-chemistry methods for biomass analysis are slow, expensive, and require significant reagents and skilled personnel. In contrast, near-infrared (NIR) spectroscopy, a faster, cost-effective, and reagent-free green technology, enables non-destructive biomass analysis with minimal sample preparation. This study provides an overview of the fundamentals of NIR spectroscopy and explores its recent applications for analyzing various biomass properties important to the biofuel and bioproduct industry. The study also critically evaluates the challenges and opportunities of using NIR spectroscopy for biomass analysis. This review aims to guide future research for rapid and high throughput characterization of biomass in the biomass industry, supporting the United Nations' sustainable development goal (SDG) 7: producing affordable and sustainable energy.

Inulin Dehydration to 5-HMF in Deep Eutectic Solvents Catalyzed by Acidic Ionic Liquids Under Mild Conditions

Valorization of carbohydrate-rich biomass by conversion into industrially relevant products is at the forefront of research in sustainable chemistry. In this work, we studied the inulin conversion into 5-hydroxymethylfurfural, in deep eutectic solvents, in the presence of acidic task-specific ionic liquids as catalysts. We employed aliphatic and aromatic ionic liquids as catalysts, and choline chloride-based deep eutectic solvents bearing glycols or carboxylic acids, as solvents. The reactions were performed in a biphasic system, with acetone as a benign extracting solvent, enabling continuous extraction of 5-HMF. We aimed to find the best experimental conditions for this transformation, in terms of catalyst loading, solvent, reaction time and temperature to achieve an economical and energy efficient process. We also analyzed the results in terms of solvent viscosity and structural organization as well as catalysts acidity, to elucidate which structural features mostly favour the reaction. Under optimized conditions, we obtained a yield in 5-HMF of 71 %, at 80 °C in 3 h. Our system can be scaled up and recycled three times with no loss in yield. Finally, comparison with the literature shows that our system achieves a higher yield under milder conditions than most protocols so far reported for the same transformation.

Insights on comprehensive characterization of distinct growth stages of Sterculia foetida pod as a potential feedstock for bioethanol production

Lignocellulosic biomass explores a sustainable and renewable energy source that could provide a suitable solution to energy demands. However, diversity is the main obstacle that hinders the biorefinery approach to bioethanol production. In this study, the non-edible feedstock, Sterculia foetida pod, green-colored skin (GSFP), and brown-colored skin (BSFP) were used as feedstock for the production of bioethanol. To examine the comprehensive characterization of selected biomass, namely BSFP and GSFP, the various methods, namely physicochemical analysis, proximate analysis, ultimate (CHNS) analysis, bulk density, and calorific value were employed. The functional group analysis, thermal stability, surface morphology, and crystallinity index for biomasses were characterized by FTIR spectroscopy, Thermo-gravimetric (TGA) analysis, scanning electron microscope (SEM), and XRD analysis. The elemental and chemical composition of GSFP and BSFP were extensively evaluated using different methods. The value-added precursors, namely cellulose and lignin isolated from GSFP and BSFP. The cellulose content in GSFP and BSFP pods was found to be 35.28 ± 3.39% and 33.95 ± 4.49% and the lignin content was 17.37 ± 3.54% and 20.79 ± 8.78% respectively. The obtained cellulose from GSFP and BSFP was subjected to two-step acid hydrolysis on different SL ratio (1:10-5:10) to prepare fermentable sugars at different concentration (g/L). Based on the different sugar concentration, the bioethanol concentration (0.91 to 18.78 g/L; 0.23 to 12.23 g/L) and specific bioethanol yield (0.44 to 1.52 g/g; 0.13 to 1.55 g/g) increased for both BSFP and GSFP respectively.

Characterization of a rare trifunctional xylanase from endophytic fungus Chaetomium globosum and its synergistic effect with cellulase cocktail

Multifunctional xylanases present considerable potential across various sectors, including the food, chemical and biorefinery industries. Herein, a novel trifunctional xylanase Xyn1.28, identified from the lignocellulose-degrading endophytic fungus Chaetomium globosum DX-THS3, exhibits high xylanase activity (230.37 ± 2.69 U/mg) along with notable endo-glucanase activity and rare arabinofuranosidase activity, which accounted for 17-33 % and 43 % of the xylanase activity, respectively. When combined with commercial cellulase cocktail Celic CTec2 at a 1:10 activity ratio, a significant synergistic effect enhanced sugar release by 27.5 % during unpretreated corn straw degradation. Alkali-treated corn cob degradation efficiency was also improved, reducing the time to achieve maximum sugar yield by 12 h. The sugar release profiles during the initial degradation stages indicated that Xyn1.28 plays a crucial role in the initial stages of hydrolyzing biomass. Furthermore, molecular docking analysis indicated that the unique site GLN-74 may significantly influence the arabinofuranosidase activity of Xyn1.28 by forming a hydrogen bond with HIS-108. Experiments involving the mutated GLN-74 further confirmed the critical role of this site in the arabinofuranosidase activity of Xyn1.28. Overall, this rare multifunctional endo-xylanase is well-positioned to facilitate the development of efficient lignocellulose degradation systems and advance cost-effective biomass conversion.

Enhancement of wheat straw pellet quality for bioenergy through additive blending

Densification of biomass through pelletizing offers a promising approach to producing clean biofuels from renewable resources. This study, which investigates the impact of additive blends on wheat straw pellet making and upgrading the physiochemical properties, has revealed exciting possibilities. Five additives, including sawdust (SD), bentonite clay (BC), corn starch (S), crude glycerol (CG), and biochar (BioC), were chosen for this study. Pellets were made from seven different combinations using a laboratory-scale pellet mill. The resulting pellets' physical and elemental properties were assessed against ISO 17,225-8 standards. Compared to control pellets, additive blends (T3-T7) exhibited significant improvements in mechanical durability (80% to 99%), tensile strength (0.36 MPa to 2.09 MPa), and bulk density (244 kg/m3 to 665.21 kg/m3), all meeting ISO standards. Additionally, these blends maintained low fines content (<2%) and water absorption capacity (<2%, except T1 and T5). Furthermore, fixed carbon content increased from 11.1% to 30.90%, and energy content rose from 17.02 MJ/kg to 20.36 MJ/kg, which showed a significant synergistic effect of blending additives. These findings underscore the potential of wheat straw as a viable biomass source for bioenergy production through pelletization, offering a hopeful outlook for the future of renewable energy. However, further research is necessary to optimize additive mixing ratios for even greater pellet quality.Implications: The study successfully demonstrated that adding specific materials during wheat straw pelletizing significantly improves the quality of the pellets as a biofuel. Here are the key implications of the statement.Wheat straw is a promising biofuel source: Densification through pelletizing makes wheat straw a viable option for renewable energy production.Additives enhance pellet quality: Sawdust, bentonite clay, corn starch, crude glycerol, and biochar improve the pellets' durability, strength, density, and energy content.Improved pellet properties meet industry standards: The resulting pellets meet ISO standards for mechanical strength, bulk density, and fines content.Synergistic effect of blending: Combining different additives leads to a greater improvement than using them individually.Need for further research: Optimizing the ratios of these additives can potentially create even better biofuel pellets.Overall, the study highlights the potential of wheat straw pelletizing with specific additives as a sustainable and efficient biofuel option. There's room for further improvement, but the initial findings are promising.

Efficient pretreatment of Phragmites australis biomass using glutamic acid for bioethanol production by a hybrid hydrolysis and fermentation strategy

Microbial fermentation of renewable lignocellulosic biomass to produce biofuels presents significant environmental advantages. The conversion of cellulose and hemicellulose into fermentable sugars provides essential carbon sources for microbial metabolism. However, the recalcitrance of biomass limits enzymatic accessibility. In this study, mild L-glutamic acid (GA) pretreatment was applied to Phragmites australis residues (reed straw) to fractionate lignin and polysaccharides for enhancing enzymatic hydrolysis. Pretreatment with 0.20 mol/L GA at 180 °C for 50 min (logRo = 4.1) achieved glucan recovery and xylan removal rates of 84.2% and 87.8%. Consequently, glucose and total sugar yields reached 75.5 and 71.2%, representing 5.35- and 5.18-fold increases compared to untreated reed. The 28.7 g fermentable sugars with a high glucose-to-xylose ratio (18.1 g/g) were obtained from 100 g reed. The hydrolysates were subsequently used as substrates for bioethanol production by Saccharomyces cerevisiae, which yielded 12.4-32.3 g/L ethanol via separate hydrolysis and fermentation (SHF). By analyzing bioethanol production of SHF and simultaneous saccharification and fermentation (SSF), an optimized hybrid hydrolysis and fermentation (HHF) strategy was developed. Under HHF process, 48.5 g/L of ethanol was achieved from 20 wt% solid loads. This study demonstrates an efficient approach to convert abundant lignocellulosic waste into fermentable sugars and biofuels.

Biofuel production from waste residuals: comprehensive insights into biomass conversion technologies and engineered biochar applications

Biomass-derived residuals represent a vital renewable energy source, offering sustainable alternatives to mitigate fossil fuel dependency, address climate change, and manage waste. Although biomass generally has a lower calorific value (10-20 MJ kg-1) compared to fossil fuels (40-50 MJ kg-1), its energy recovery potential can be enhanced through advanced conversion technologies such as torrefaction, pyrolysis, and gasification. Additionally, biomass is considered carbon neutral when sourced sustainably, as the CO2 released during combustion is reabsorbed by plants during their regrowth cycle, maintaining a balanced carbon flux in the atmosphere. This review explores the diverse sources of biomass and examines their chemical compositions and inherent properties, emphasizing their transformation into valuable energy carriers and bio-products. It provides a comprehensive analysis of thermochemical, biochemical, and physicochemical conversion technologies, detailing their mechanisms, efficiencies and applications. Special attention is given to biochar, a product of biomass pyrolysis, highlighting its potential in pollution mitigation, carbon sequestration, and as a catalyst in industrial applications. The review delves into synthesis processes of biochar and performance-enhancing modifications, illustrating its significant role in sustainable environmental management. Additionally, the economic and ecological advantages of biomass-derived energy, including reduced greenhouse gas emissions and waste reutilization, are critically evaluated, underscoring its superiority over conventional fossil fuels. Challenges limiting the scalability of biomass energy, such as technology costs, process efficiency, and market dynamics, are addressed, alongside prospective solutions. By consolidating extensive research on biomass conversion technologies and engineered biochar applications, this review serves as a valuable resource for researchers and policymakers. It aims to guide advancements in biomass utilization, fostering a transition toward sustainable energy systems and addressing global energy and environmental challenges.

A distinct autofluorescence distribution pattern marks enzymatic deconstruction of plant cell wall

Achieving an economically viable transformation of plant cell walls into bioproducts requires a comprehensive understanding of enzymatic deconstruction. Microscale quantitative analysis offers a relevant approach to enhance our understanding of cell wall hydrolysis, but becomes challenging under high deconstruction conditions. This study comprehensively addresses the challenges of quantifying the impact of extensive enzymatic deconstruction on plant cell wall at microscale. Investigation of highly deconstructed spruce wood provided spatial profiles of cell walls during hydrolysis with remarkable precision. A distinct cell wall autofluorescence distribution pattern marking enzymatic hydrolysis along with an asynchronous impact of hydrolysis on cell wall structure, with cell wall volume reduction preceding cell wall accessible surface area decrease, were revealed. This study provides novel insights into enzymatic deconstruction of cell wall at under-investigated cell scale, and a robust computational pipeline applicable to diverse biomass species and pretreatment types for assessing hydrolysis impact and efficiency.

Biological-chemical conversion process design and machine learning-related life cycle assessment: Bio-lubricant production in a real case study of South Korea

This study explores the production of poly alpha olefin (PAO) from biomass as an environmentally friendly alternative to fossil fuel-based methods, aiming to reduce greenhouse gas (GHG) emissions. The primary goal is to design a process for converting 2,000 metric tons of biomass into PAO daily, integrating biological and chemical pathways. Environmental impact is assessed through a life cycle assessment (LCA), comparing this biomass-based method with traditional fossil fuel-derived processes. Key findings include the successful production of 458 metric tons of PAO, with the LCA revealing a 34.8% reduction in GHG emissions (9.88 kg CO2-eq./kg of PAO) compared to fossil fuel-based PAO. Sensitivity analyses on the oligomerization yield (60-70%, base case at 65%) and the recycle ratio of glucose in the bioprocess for octanoic acid production show significant environmental benefits when exceeding a 55% recycle ratio. Additionally, an energy scenario analysis predicts the impact of shifting to renewable energy by 2030. In a scenario where all electric utilities are renewable (RE100 scenario), GHG emissions are estimated at 13.07 kg CO2-eq./kg of PAO, further emphasizing the environmental advantage of biomass-based PAO. This study, through its integration of biological and chemical processes and comprehensive LCA, provides critical insights into the potential of biomass-based materials for reducing GHG emissions, making a substantial contribution to future research in high-value material production from renewable resources.

Mycoprotein: A Healthy and Sustainable Source of Alternative Protein-Based Foods

Perhaps the most important challenge currently facing agrifood is how to ensure a more sustainable food system by changing the way we eat. Fermentation of fungi to produce mycoprotein can address this imperative by utilizing an age-old technology and a largely untapped natural resource. In this review, we look at the origins of mycoprotein, fermentation at scale, and downstream applications of mycoprotein as food. We review the advances in our understanding of the underpinning science from fermentation through to food development and the evidence base of research that provides insights into the impacts of diets rich in mycoprotein on both the health of our bodies and the environment. We show that mycoprotein has a valuable and future-facing role as a healthy new protein with a low environmental impact.

Advancing hydrothermal carbonization: Assessing hydrochar's role and challenges in carbon sequestration

The increasing urgency to reduce atmospheric CO2 emissions has driven research into sustainable carbon sequestration technologies, with hydrochar (HC) emerging as a promising material. HC is derived from hydrothermal carbonization (HTC), a thermochemical process that converts biomass into a carbon-rich solid at moderate temperatures and self-generated pressure in an aqueous environment. Due to its unique reaction pathways, HC differs significantly from biochar (BC) derived from pyrolysis in terms of application, performance, and structural characteristics. Despite HC's potential for long-term carbon storage, critical gaps remain in understanding its sequestration mechanisms, influencing factors, and optimization strategies-hindering its effective application. This review critically evaluates HC's carbon sequestration capacity, focusing on overlooked complexities that influence its performance. Key parameters, including feedstock composition, reaction temperature, pH, and residence time, are systematically examined to elucidate their impact on HC's structural integrity and carbon stability. Special attention is given to the role of lignin in enhancing stability and thermal resilience, as well as the concept of carbon-ash recalcitrance, where mineral embedding enhances carbon stability. To assess HC's long-term sequestration effectiveness, this study analyzes key indicators such as thermal stability, chemical resilience, aromaticity, and dissolved organic carbon (DOC) leaching.Besides, this review explores innovative strategies for improving HC's sequestration performance, including HTC liquid recycling, chemical modification, and salinity control. By integrating expert-driven insights and identifying research gaps, this synthesis advances theoretical understanding while outlining future directions for optimizing HC as a sustainable carbon sink. Ultimately, this work establishes HC as a critical material in global carbon management efforts and climate change mitigation.

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.

Zymomonas mobilis: bringing an ancient human tool into the genomic era

Zymomonas mobilis is an ethanologenic bacterium that has been used for over 1500 years to produce alcoholic beverages. Recently, this microbe has become a top candidate for biofuel production due to its efficient metabolism. Z. mobilis is being developed to utilize lignocellulosic biomass as a feedstock and synthesize a range of valuable chemicals and fuels. Genetic and metabolic engineering strategies are crucial to reach these goals. Recent advances include genome engineering, CRISPR editing, and CRISPRi knockdown of genes. Metabolic engineering has enabled redirection of carbon from the natural product ethanol to chemicals such as 2,3-butanediol and polyhydroxybutyrate. The approaches summarized here will streamline the development of Z. mobilis as an industrial chassis for sustainable liquid fuels and chemicals.

Lignin from Plant-Based Agro-Industrial Biowastes: From Extraction to Sustainable Applications

Lignin, the most abundant aromatic polymer in nature, plays a critical role in lignocellulosic biomasses by providing structural support. However, its presence complicates the industrial exploitation of these materials for biofuels, paper production and other high-value compounds. Annually, the industrial extraction of lignin reaches an estimated 225 million tons, yet only a fraction is recovered for reuse, with most incinerated as low-value fuel. The growing interest in lignin potential has sparked research into sustainable recovery methods from lignocellulosic agro-industrial wastes. This review examines the chemical, physical and physicochemical processes for isolating lignin, focusing on innovative, sustainable technologies that align with the principles of a circular economy. Key challenges include lignin structural complexity and heterogeneity, which hinder its efficient extraction and application. Nonetheless, its properties such as high thermal stability, biodegradability and abundant carbon content place lignin as a promising material for diverse industrial applications, including chemical synthesis and energy generation. A structured analysis of advancements in lignin extraction, characterization and valorization offers insights into transforming this undervalued by-product into a vital resource, reducing reliance on non-renewable materials while addressing environmental sustainability.

Can agriculture and food waste be a solution to reduce environmental impact of plastic pollution? zero-waste approach for sustainable clean environment

Agriculture and food waste, especially from fruits, vegetables, and plant byproducts like banana peels, avocado seeds, and durian seeds, have emerged as promising alternatives for bioplastic production. These materials, rich in polysaccharides and cellulose, offer a sustainable solution to reduce plastic pollution and mitigate the environmental impact of traditional plastics. This review focuses on the potential of utilizing agricultural and food waste to create starch-based bioplastics, emphasizing the importance of a zero-waste approach to enhance the economic value of these byproducts while promoting a cleaner environment. We include a SWOT analysis of this innovative approach, assess the environmental implications of bioplastic production, and highlight the potential for turning agricultural waste into a key player in the fight against plastic pollution. This review also explores the future prospects of harnessing agriculture and food waste as valuable resources for sustainable bioplastics, contributing to a greener, more sustainable world.

A Strategy Towards the Valorization of Aloe Vera Rinds to Obtain Crystalline Cellulose: Pretreatment Effects and Elemental Analysis

Although crystalline nanocellulose (CNCs) can be extracted from different resources, the employed pretreatments, which disrupt the inter- and intramolecular physical interactions, depend on the biomass sources. This study aims to valorize Aloe Vera (AV) rinds into cellulose and crystalline nanocellulose (CNC) employing two approaches during hydrolysis: sulfuric acid (CNCSA) and citric acid (CNCCA) after 30, 60, and 90 min of reaction. The effects of pretreatments and hydrolysis time on the functional groups and hydrogen bonding in biomass are discussed. Crystalline structure (polymorph type), crystallinity, thermal stability, morphology, particle size, and metal presence are also analyzed. A transformation from type I into II polymorph was achieved, where the intermolecular interactions governing cellulose were increased in CNCSA and were almost maintained in CNCCA. Properties based on the structure, thermal properties, particle size, and metal presence indicate that the CNCSA30 and CNCCA90 samples displayed potential application as reinforcement agents for other types of polymers having no more melting points of 160 and 220 °C, respectively.

A simple three-dimensional microfluidic platform for studying chemotaxis and cell sorting

Microbial chemotaxis plays a key role in a diversity of biological and ecological processes. Although microfluidics-based assays have been applied to investigate bacterial chemotaxis, retrieving chemotactic cells off-chip based on their dynamic chemotactic responses remains limited. Here, we present a simple three-dimensional microfluidic platform capable of programmable delivery of solutions, maintaining static, stable gradients for over 20 hours, followed by active sorting and retrieval of bacteria based on their chemotactic phenotypes. Using this platform, we revealed the swimming features of individual E. coli cells in response to chemoattractant and observed rapid bacterial adaptation to the gradients. Furthermore, the robust performance of the platform allowed us to investigate complex natural microbial communities. Exemplified by sorting bacteria towards soluble cellulose and lignin compounds, we found only a small percentage (<20%) of chemotactic bacteria from a leaf mould microbiota exhibited cellulolytic or lignin-degradation abilities. These findings highlight that chemotaxis does not always align with degradation abilities. Interestingly, a new Erwinia aphidicola strain was discovered with substantial cellulose degradation capabilities. These results illustrate the strong potential of this microfluidic platform for investigating broad processes involving bacterial chemotaxis and for discovering functional microbes.

Fungal lignocellulolytic enzymes: an in silico and full factorial design approach

Efficient degradation of lignocellulosic biomass is key for the production of value-added products, contributing to sustainable and renewable solutions. This study employs a two-step approach to evaluate lignocellulolytic enzymes of Ceratocystis paradoxa, Colletotrichum falcatum, and Sporisorium scitamineum. First, an in silico genomic analysis was conducted to predict the potential enzyme groups produced by these fungi. Second, a 2³ full factorial design of solid-state cultivation was employed to investigate the cultivation conditions that optimize enzyme activity. In silico analysis of phytopathogen genomes identified proteins with the potential for biomass degradation. Cellulase and phenoloxidase activities were assessed in culture medium and solid-state cultivation. A 2³ full factorial design was employed for solid-state cultivation to evaluate the cellulose, endoglucanase, and laccase activities. In silico analysis shows that C. falcatum has the most diverse enzyme set for lignocellulosic biomass degradation. In vitro assays corroborate this, demonstrating that C. falcatum produces the highest enzyme quantities, except for cellulase, where C. paradoxa outperforms it. Both C. paradoxa and C. falcatum exhibit cellulase and phenoloxidase activities, but only C. falcatum shows laccase activity. Most favorable enzyme production in solid-state cultivation occurred with 85-95 g 100 g- 1 bagasse moisture and 5 g 100 g- 1 yeast extract, with four-day cultivation period needed for cellulase and endoglucanase in C. paradoxa and 12 days for endoglucanase and laccase in C. falcatum. The in silico and in vitro assays demonstrated that C. falcatum can produce a diverse enzyme set, including laccase, cellulase, and endoglucanase, making it a promising candidate for enzymatic industrial applications.

Advances in fungal sugar transporters: unlocking the potential of second-generation bioethanol production

Second-generation (2G) bioethanol production, derived from lignocellulosic biomass, has emerged as a sustainable alternative to fossil fuels by addressing growing energy demands and environmental concerns. Fungal sugar transporters (STs) play a critical role in this process, enabling the uptake of monosaccharides such as glucose and xylose, which are released during the enzymatic hydrolysis of biomass. This mini-review explores recent advances in the structural and functional characterization of STs in filamentous fungi and yeasts, highlighting their roles in processes such as cellulase induction, carbon catabolite repression, and sugar signaling pathways. The review also emphasizes the potential of genetic engineering to enhance the specificity and efficiency of these transporters, overcoming challenges such as substrate competition and limited pentose metabolism in industrial strains. By integrating the latest research findings, this work underscores the pivotal role of fungal STs in optimizing lignocellulosic bioethanol production and advancing the bioeconomy. Future prospects for engineering transport systems and their implications for industrial biotechnology are also discussed. KEY POINTS: STs present a conserved structure with different sugar affinities STs are involved in the signaling and transport of sugars derived from plant biomass Genetic engineering of STs can improve 2G bioethanol production.

Raw biowaste conversion to high-value compounds for food, cosmetic and pharmaceutical industries

Biowaste valorisation into high-value compounds is one of the main challenges of green chemistry, as chemicals produced from biological sources are identified as key substances in the development of a low-carbon and circular bioeconomy in connection with the transition from fossil to renewable feedstocks. The review summarizes the production of high-value products such as glucose-based chemicals, phenolic compounds and volatile-fatty acids prepared from biomass waste. Biowaste pretreatment methods such as milling, filtration and extraction followed by current non-catalytic methods such as microwave or ultrasound extraction and catalytic methods for the production value-added compounds in the presence of various catalyst types in conventional, nano or enzyme form are listed with a focus on value-added chemicals applied in the food, cosmetic and pharmaceutical industries. The economic feasibility, technical aspects and concept of the biorefinery are briefly mentioned, emphasizing the necessity of life cycle assessment for each bioproduct and technological process. Finally, it provides a future perspective and makes recommendations for potential research strategies, recognizing the importance of utilizing biomass waste for the production of useful compounds as an attractive and environmentally friendly approach whose development should be encouraged. The utilization of biowaste for high-value chemicals production shows high potential, however, there are still many challenges to be resolved throughout the entire production chain, reflecting technological, economic, ecological, sociological and long-term issues.

Bioethanol production from potatoes in India: A SWOT analysis

India is the third-largest energy consumer globally, heavily reliant on imported oil. Projections suggest India's energy consumption will double by 2050, posing challenges to energy security and leading to significant foreign currency outflows. The extensive use of fossil fuels increases carbon emissions, raising environmental and health concerns. In this context, bioethanol production from potatoes offers a promising solution. This paper presents a SWOT analysis of this potential. Strengths include potatoes' widespread availability, high starch content, and compatibility with existing infrastructure. However, weaknesses such as seasonal cultivation, water-intensive farming, and competition with food demand require strategic solutions. Opportunities for bioethanol production from potatoes are numerous, including rural development, reduced fossil fuel reliance, and supportive governmental policies promoting renewable energy. Yet, threats like market fluctuations, technological limitations, and environmental issues related to land use and water consumption challenge the feasibility of this venture. This SWOT analysis provides insights into the strengths, weaknesses, opportunities, and threats associated with bioethanol production from potatoes in India, highlighting the potential and challenges of this renewable energy pathway.

Plant cell wall enzymatic deconstruction: Bridging the gap between micro and nano scales

Understanding lignocellulosic biomass resistance to enzymatic deconstruction is crucial for its sustainable conversion into bioproducts. Despite scientific advances, quantitative morphological analysis of plant deconstruction at cell and tissue scales remains under-explored. In this study, an original pipeline is devised, involving four-dimensional (space  + time) fluorescence confocal imaging, and a novel computational tool, to track and quantify deconstruction at cell and tissue scales. By applying this pipeline to poplar wood, dynamics of cellular parameters was computed and cellulose conversion during enzymatic deconstruction was measured. Results showed that enzymatic deconstruction predominantly impacts cell wall volume rather than surface area. Additionally, a negative correlation was observed between pre-hydrolysis compactness measures and volumetric cell wall deconstruction rate, whose strength was modulated by enzymatic activity. Results also revealed a strong positive correlation between average volumetric cell wall deconstruction rate and cellulose conversion rate. These findings link key deconstruction parameters across nano and micro scales.

From lignocellulosic biomass to single cell oil for sustainable biomanufacturing: Current advances and prospects

As global temperatures rise and arid climates intensify, the reserves of Earth's resources and the future development of humankind are under unprecedented pressure. Traditional methods of food production are increasingly inadequate in meeting the demands of human life while remaining environmentally sustainable and resource-efficient. Consequently, the sustainable supply of lipids is expected to become a pivotal area for future food development. Lignocellulose biomass (LB), as the most abundant and cost-effective renewable resource, has garnered significant attention from researchers worldwide. Thus, bioprocessing based on LB is appearing as a sustainable model for mitigating the depletion of energy reserves and reducing carbon footprints. Currently, the transformation of LB primarily focuses on producing biofuels, such as bioethanol, biobutanol, and biodiesel, to address the energy crisis. However, there are limited reports on the production of single cell oil (SCO) from LB. This review, therefore, provides a comprehensive summary of the research progress in lignocellulosic pretreatment. Subsequently, it describes how the capability for lignocellulosic use can be conferred to cells through genetic engineering. Additionally, the current status of saccharification and fermentation of LB is outlined. The article also highlights the advances in synthetic biology aimed at driving the development of oil-producing microorganism (OPM), including genetic transformation, chassis modification, and metabolic pathway optimization. Finally, the limitations currently faced in SCO production from straw are discussed, and future directions for achieving high SCO yields from various perspectives are proposed. This review aims to provide a valuable reference for the industrial application of green SCO production.

Analysis of detoxification kinetics and end products of furan aldehydes in Acinetobacter baylyi ADP1

The efficient utilization of lignocellulosic hydrolysates in bioprocesses is impeded by their complex composition and the presence of toxic compounds, such as furan aldehydes, formed during lignocellulose pretreatment. Biological detoxification of these furan aldehydes offers a promising solution to enhance the utilization of lignocellulosic hydrolysates. Acinetobacter baylyi ADP1 is known to metabolize furan aldehydes, yet the complete spectrum of reaction products and dynamics remains unclear. Here, we determined the detoxification metabolites of furfural and 5-hydroxymethylfurfural in A. baylyi ADP1 and studied the kinetics of detoxification. The results indicate that detoxification in A. baylyi ADP1 follows a typical alcohol-aldehyde-acid scheme, with furoic acid and 5-hydroxymethyl-2-furancarboxylic acid as the final products for furfural and 5-hydroxymethylfurfural, respectively. Both end products were found to be less toxic for cells than their unmodified forms. These findings underscore the potential of A. baylyi ADP1 in detoxifying lignocellulosic hydrolysates for bioprocess applications.

Advancing Lignocellulosic Biomass Fractionation through Molten Salt Hydrates: Catalyst-Enhanced Pretreatment for Sustainable Biorefineries

Developing a process that performs the lignocellulosic biomass fractionation under milder conditions simultaneously with the depolymerization and/or the upgrading of all fractions is fundamental for the economic viability of future lignin-first biorefineries. The molten salt hydrates (MSH) with homogeneous or heterogeneous catalysts are a potential alternative to biomass pretreatment that promotes cellulose's dissolution and its conversion to different platform molecules while keeping the lignin reactivity. This review investigates the fractionation of lignocellulosic biomass using MSH to produce chemicals and fuels. First, the MSH properties and applications are discussed. In particular, the use of MSH in cellulose dissolution and hydrolysis for producing high-value chemicals and fuels is presented. Then, the biomass treatment with MSH is discussed. Different strategies for preventing sugar degradation, such as biphasic media, adsorbents, and precipitation, are contrasted. The potential for valorizing isolated lignin from the pretreatment with MSH is debated. Finally, challenges and limitations in utilizing MSH for biomass valorization are discussed, and future developments are presented.

Sequential pretreatment with hydroxyl radical and manganese peroxidase for the efficient enzymatic saccharification of corn stover

BACKGROUND

White rot fungi produce various reactive oxygen species and ligninolytic enzymes for lignocellulose deconstruction. However, their interactions during the deconstruction of lignocellulosic structural barriers for efficient enzymatic saccharification remain unclear.

RESULTS

Herein, the extracellular enzyme activities and secretomic analysis revealed the sequential expression of hydroxyl radical (⋅OH) and manganese peroxidases (MnPs) for lignocellulose deconstruction by the white rot fungus Irpex lacteus. Subsequently, in vitro functional studies found that ⋅OH possessed the ability to disrupt the smooth surface structure of corn stover, resulting in increased enzymatic saccharification and cellulose accessibility. Purified recombinant MnPs from I. lacteus were able to cleave the β-O-4 bond in phenolic and non-phenolic lignin model dimers without the help of any mediators. Furthermore, the sequential pretreatment of corn stover with ⋅OH and MnP exhibited significant synergistic effects, increasing enzymatic saccharification and cellulose accessibility by 2.9-fold and 1.8-fold, respectively.

CONCLUSIONS

These results proved for the first time the synergistic effects of ⋅OH and MnP pretreatment in improving the enzymatic saccharification and cellulose accessibility of corn stover. These findings also demonstrated the potential application of ⋅OH and MnP pretreatment for the efficient enzymatic saccharification of corn stover.

Microwave-Assisted Pyrolysis-A New Way for the Sustainable Recycling and Upgrading of Plastic and Biomass: A Review

The efficient utilization of organic solid waste resources can help reducing the consumption of conventional fossil fuels, mitigating environmental pollution, and achieving green sustainable development. Due to its dual nature of being both a resource and a source of pollution, it is crucial to implement suitable recycling technologies throughout the recycling and upgrading processes for plastics and biomass, which are organic solid wastes with complex mixture of components. The conventional pyrolysis and hydropyrolysis were summarized for recycling plastics and biomass into high-value fuels, chemicals, and materials. To enhance reaction efficiency and improve product selectivity, microwave-assisted pyrolysis was introduced to the upgrading of plastics and biomass through efficient energy supply especially with the aid of catalysts and microwave absorbers. This review provides a detail summary of microwave-assisted pyrolysis for plastics and biomass from the technical, applied, and mechanistic perspectives. Based on the recent technological advances, the future directions for the development of microwave-assisted pyrolysis technologies are predicted.

Dissolving Chitin by Novel Deep Eutectic Solvents for Effectively Enzymatic Hydrolysis

Chitin is the most productive nitrogen-containing polysaccharide in nature with immense potential for transforming into a range of chemicals. However, its dense crystal structure poses a challenge for depolymerization, limiting its applications. To overcome these challenges, a novel series of deep eutectic solvents (DESs) based on benzyltrimethylammonium chloride (TMBAC) as the hydrogen bond acceptor was developed. These TMBAC-based DESs, in combination with lactic acid, oxalic acid, and malic acid as the hydrogen bond donor demonstrated efficient chitin dissolution, achieving a solubility of up to 12% and an 88% recovery rate of regenerated chitin. The regenerated chitin was characterized using XRD, FT-IR, SEM, and 13C CP-MAS NMR, which indicated the preservation of chitin's chemical structure, a significant decrease in crystallinity, and a reduction in the molecular weight. Furthermore, the enzymatic hydrolysis efficiency of chitin was nearly doubled after treatment with TMBAC-based DESs, surpassing the effectiveness of untreated chitin. This approach holds promise for facilitating subsequent transformation and utilization of chitin.

Biowaste rice husk derived cellulosic hydrogel incorporating industrial cotton waste nonwoven for wound dressing

Bio-wastes are organic materials achieved through biological sources. The rice crop produces a substantial amount of biowaste in the form of rice husk, which is rich in cellulose. In this research, cellulose was extracted from rice husk by alkalization and bleaching process. The rice husk extracted cellulose was further used to develop cellulose hydrogel by using the sol-gel technique. The nonwoven fabric of industrial cotton waste was developed in three different GSM (50, 100, and 150). The nonwoven fabric was incorporated in the cellulose hydrogel having three different concentrations (1 %, 2 %, and 3 %) to develop the hydrogel non-woven cotton fabric composite for sustainable wound dressing applications. Moreover, prepared rice husk extracted cellulose hydrogel loaded with AgNO3 (0.5 %, 1 %, and 1.5 %) for achieving antibacterial characteristics. The Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were employed to confirm the existence of cellulose hydrogel layers within the cotton nonwoven composite. The developed hydrogel S12 exhibited a maximum fluid absorbency of 1281.84 % with a tensile strength of 28.6 N and elongation of 40.96 %. The results show successful rice husk extracted cellulose hydrogel formation, exhibiting structural stability, excellent exudate absorbency and moisture management, antimicrobial efficacy, and sustainability.

Valorization of residual lignin from corncob residues into thermosensitive lignin-based "molecular glues" for recycling cellulase

The cost of enzymolysis is a major bottleneck for the industrialisation of lignocellulosic enzymatic hydrolysis technology, and recycling cellulase can reduce this cost. Herein, a sulfobetaine prepolymer (CPS) with terminal chlorine was grafted onto enzymatic hydrolysis residual lignin (EHL) from corncob to construct thermosensitive lignin-based "molecular glues" (lignin-based sulfobetaine polymers, L-CPS) that were used to recover and recycle cellulase. L-CPS2 (1.0 g/L) was added to the corncob residue (CCR) enzymolysis system (50 °C, pH 4.5). After hydrolysis, L-CPS2 co-precipitated with cellulase through hydrophobic binding when cooling to 25 °C. This co-precipitation decreased the amount of cellulase by 40 %. In summary, a thermally responsive lignin-based molecular glue was constructed for green recycling of cellulase, providing a new approach to decreasing the cost of lignocellulosic enzymolysis and high value utilisation of industrial lignin.

Engineered reduction of S-adenosylmethionine alters lignin in sorghum

BACKGROUND

Lignin is an aromatic polymer deposited in secondary cell walls of higher plants to provide strength, rigidity, and hydrophobicity to vascular tissues. Due to its interconnections with cell wall polysaccharides, lignin plays important roles during plant growth and defense, but also has a negative impact on industrial processes aimed at obtaining monosaccharides from plant biomass. Engineering lignin offers a solution to this issue. For example, previous work showed that heterologous expression of a coliphage S-adenosylmethionine hydrolase (AdoMetase) was an effective approach to reduce lignin in the model plant Arabidopsis. The efficacy of this engineering strategy remains to be evaluated in bioenergy crops.

RESULTS

We studied the impact of expressing AdoMetase on lignin synthesis in sorghum (Sorghum bicolor L. Moench). Lignin content, monomer composition, and size, as well as biomass saccharification efficiency were determined in transgenic sorghum lines. The transcriptome and metabolome were analyzed in stems at three developmental stages. Plant growth and biomass composition was further evaluated under field conditions. Results evidenced that lignin was reduced by 18% in the best transgenic line, presumably due to reduced activity of the S-adenosylmethionine-dependent O-methyltransferases involved in lignin synthesis. The modified sorghum features altered lignin monomer composition and increased lignin molecular weights. The degree of methylation of glucuronic acid on xylan was reduced. These changes enabled a ~20% increase in glucose yield after biomass pretreatment and saccharification compared to wild type. RNA-seq and untargeted metabolomic analyses evidenced some pleiotropic effects associated with AdoMetase expression. The transgenic sorghum showed developmental delay and reduced biomass yields at harvest, especially under field growing conditions.

CONCLUSIONS

The expression of AdoMetase represents an effective lignin engineering approach in sorghum. However, considering that this strategy potentially impacts multiple S-adenosylmethionine-dependent methyltransferases, adequate promoters for fine-tuning AdoMetase expression will be needed to mitigate yield penalty.

Renewable hemicellulose-based materials for value-added applications

The importance of renewable resources and environmentally friendly materials has grown globally in recent time. Hemicellulose is renewable lignocellulosic materials that have been the subject of substantial valorisation research. Due to its distinctive benefits, including its wide availability, low cost, renewability, biodegradability, simplicity of chemical modification, etc., it has attracted increasing interest in a number of value-added fields. In this review, a systematic summarizes of the structure, extraction method, and characterization technique for hemicellulose-based materials was carried out. Also, their most current developments in a variety of value-added adsorbents, biomedical, energy-related, 3D-printed materials, sensors, food packaging applications were discussed. Additionally, the most recent challenges and prospects of hemicellulose-based materials are emphasized and examined in-depth. It is anticipated that in the near future, persistent scientific efforts will enable the renewable hemicellulose-based products to achieve practical applications.

Structure changes of lignin and their effects on enzymatic hydrolysis for bioethanol production: a focus on lignin modification

Enzymatic hydrolysis contributes to obtaining fermentable sugars using pretreated lignocellulose materials for bioethanol generation. Unfortunately, the pretreatment of lignocellulose causes low substrate enzymatic hydrolysis, which is due to the structure changes of lignin to produce main phenolic by-products and non-productive cellulase adsorption. It is reported that modified lignin enhances the speed of enzymatic hydrolysis through single means to decrease the negative effects of fermentation inhibitors or non-productive cellulase adsorption. However, a suitable modified lignin should be selected to simultaneously reduce the fermentation inhibitors concentration and non-productive cellulase adsorption for saving resources and maximizing the enzymatic hydrolysis productivity. Meanwhile, the adsorption micro-mechanisms of modified lignin with fermentation inhibitors and cellulase remain elusive. In this review, different pretreatment effects toward lignin structure, and their impacts on subsequent enzymatic hydrolysis are analyzed. The main modification methods for lignin are presented. Density functional theory is used to screen suitable modification methods for the simultaneous reduction of fermentation inhibitors and non-productive cellulase adsorption. Lignin-fermentation inhibitors and lignin-cellulase interaction mechanisms are discussed using different advanced analysis techniques. This article addresses the gap in previous reviews concerning the application of modified lignin in the enhancement of bioethanol production. For the first time, based on existing studies, this work posits the hypothesis of applying theoretical simulations to screen efficient modified lignin-based adsorbents, in order to achieve a dual optimization of the detoxification and saccharification processes. We aim to improve the integrated lignocellulose transformation procedure for the effective generation of cleaner bioethanol.

Applications, challenges and prospects of superabsorbent polymers based on cellulose derived from lignocellulosic biomass

The synthetic superabsorbent polymers (SAPs) market is experiencing significant growth, with applications spanning agriculture, healthcare, and civil engineering, projected to increase from $9.0 billion USD in 2019 to $12.9 billion USD by 2024. Despite this positive trend, challenges such as fluctuating raw material costs and lower biodegradability of fossil fuel-based SAPs could impede further expansion. In contrast, cellulose and its derivatives present a sustainable alternative due to their renewable, biodegradable, and abundant characteristics. Lignocellulosic biomass (LCB), rich in cellulose and lignin, shows promise as a source for eco-friendly superabsorbent polymer (SAP) production. This review discusses the applications, challenges, and future prospects of SAPs derived from lignocellulosic resources, focusing on the cellulose extraction process through fractionation and various modification and crosslinking techniques. The review underscores the potential of cellulose-based SAPs to meet environmental and market needs, offering a viable path forward in the quest for more sustainable materials.

Review of energy self-circulation systems integrating biogas utilization with Powerfuels production in global livestock industry

Energy self-circulation systems, defined as energy systems incorporating the recycling utilization of waste biomass, have been proposed to reduce greenhouse gases emissions from livestock sector. In this study, a comprehensive review of the situation and challenges of biogas utilization in the livestock industry was provided. Moreover, two technological routes were proposed for a circular livestock system combined with Powerfuels production (CP-CLS), starting from biogas combustion for power generation and steam reforming to the sustainable development path of synthesizing, storing, and utilizing Powerfuels. The self-circulation capability and comprehensive benefits of the CP-CLS life cycle was discussed, along with future application scenarios and proposed standards for Powerfuels. To realize this potential, continuous research, development, and policy support are crucial. This study envisions the next generation of energy self-circulation systems, which expects to reduce the negative effect of livestock industry on climate change and promote sustainable development.

Bioaugmentation protocols involving Methanobrevibacter thaueri and Pecoramyces ruminantium for investigating lignocellulose degradation and methane production from alfalfa stalks

Two protocols involving batch cultures were used to investigate the bioaugmentation of methane production by Pecoramyces ruminantium, and Methanobrevibacter thaueri. Protocol I examined the effect of altering the proportion of the microbial constituents in inoculum on alfalfa stalk fermentations and showed a 25 % improvement in dry matter loss in cultures where the inoculum contained just 30 % of co-culture and 70 % of fungal monoculture. Protocol II involved consecutive cultures and alternating inoculations. This protocol resulted in 17-22 mL/g DM methane production with co-cultures a 30 % increase in methane relative to the fungal monoculture. Both protocols indicate that the co-culture rapidly dominated and was more resilient than the monoculture. Synergistic interaction between fungus and methanogen, promoted more efficient lignocellulose degradation and higher methane yield. This study highlighted the potential of microbial co-cultures for enhancing methane production from lignocellulosic biomass, offering a promising bioaugmentation strategy for improving biogas yields and waste valorization.

Industrial biotechnology goes thermophilic: Thermoanaerobes as promising hosts in the circular carbon economy

Transitioning away from fossil feedstocks is imperative to mitigate climate change, and necessitates the utilization of renewable, alternative carbon and energy sources to foster a circular carbon economy. In this context, lignocellulosic biomass and one-carbon compounds emerge as promising feedstocks that could be renewably upgraded by thermophilic anaerobes (thermoanaerobes) via gas fermentation or consolidated bioprocessing to value-added products. In this review, the potential of thermoanaerobes for cost-efficient, effective and sustainable bioproduction is discussed. Metabolic and bioprocess engineering approaches are reviewed to draw a comprehensive picture of current developments and future perspectives for the conversion of renewable feedstocks to chemicals and fuels of interest. Selected bioprocessing scenarios are outlined, offering practical insights into the applicability of thermoanaerobes at a large scale. Collectively, the potential advantages of thermoanaerobes regarding process economics could facilitate an easier transition towards sustainable bioprocesses with renewable feedstocks.

Enzyme immobilization with nanomaterials for hydrolysis of lignocellulosic biomass: Challenges and future Perspectives

Enzyme immobilization has emerged as a prodigious strategy in the enzymatic hydrolysis of lignocellulosic biomass (LCB) promising enhanced efficacy and stability of the enzymes. Further, enzyme immobilization on magnetic nanoparticles (MNPs) facilitates the easy recovery and reuse of biocatalysts. This results in the development of a nanobiocatalytic system, that serves as an eco-friendly and inexpensive LCB deconstruction approach. This review provides an overview of nanomaterials used for immobilization with special emphasis on the nanomaterial-enzyme interactions and strategies of immobilization. After the succinct outline of the immobilization procedures and supporting materials, a comprehensive assessment of the catalysis enabled by nanomaterial-immobilized biocatalysts for the conversion and degradation of lignocellulosic biomasses is provided by gathering state-of-the-art examples. The challenges and future directions associated with this technique providing a potential solution in the present article. Insight on the recent advancements in the process of nanomaterial-based immobilization for the hydrolysis of lignocellulosic biomass has also been highlighted in the article.

Furfural as a low-volume, high-value asset from agricultural residues: A review on production, agricultural applications and environmental sustainability

This comprehensive review explores furfural production from agricultural residues, focusing on its significance as a low-volume, high-value asset crucial for environmental sustainability. It covers diverse production technologies, recent advancements, and applications in agriculture, evaluating furfural's potential to enhance crop resilience and yield. Showing its role in a circular economy, the review discusses how furfural can replace conventional petrochemical processes, thereby reducing environmental impact. Case studies, such as successful implementations with cotton biomass byproducts, illustrate furfural's practical applications and environmental benefits. The study underscores the need for ongoing research, supportive policies, and furfural's growing role in sustainable agriculture and industry. It is focused on furfural's essential contribution to promoting environmental stewardship and sustainable practices. By examining furfural's role as a value-added product from agricultural residues, this review provides insights into its economic viability and potential challenges.

Advanced anaerobic digestion of household food waste pretreated by in situ-produced mixed enzymes via solid-state fermentation: Feasibility and application perspectives

Enzymatic pretreatment is an effective method which can improve the anaerobic digestion (AD) efficiency of household food waste (HFW). As an alternative to expensive commercial enzymes, mixed enzymes (MEs) produced in situ from HFW by solid-state fermentation (SSF) can greatly promote the hydrolysis rate of HFW and achieve advanced anaerobic digestion (AAD) economically sustainable. In this paper, strategies for improving the efficiency of the enzyme-production process and the abundance of MEs are briefly discussed, including SSF, fungal co-cultivation, and stepwise fermentation. The feasibility of using HFW as an applicable substrate for producing MEs (amylase, protease, and lignocellulose-degrading enzymes) and its potential advantages in HFW anaerobic digestion are comprehensively illustrated. Based on the findings, an integrated AAD process of HFW pretreated with MEs produced in situ was proposed to maximise bioenergy recovery. The mass balance results showed that the total volatile solids removal rate could reach 98.56%. Moreover, the net energy output could reach 2168.62 MJ/t HFW, which is 9.79% higher than that without in situ-produced MEs and pretreatment. Finally, perspectives for further study are presented.

Thermodynamic modeling of freeze pretreatment in the destruction of rice straw structure combined with alkaline-hydrothermal method for enzymatic hydrolysis

Freeze pretreatment combined with alkaline-hydrothermal method of rice straw for enzymatic hydrolysis was studied. Crystallization stress in the rice stem pores caused by water freezing at -20- -40 °C was modeled to illustrate the destruction mechanism. The stress was calculated as 22.5-38.3 MPa that were higher than the tensile yield stress of untreated stems (3.0 MPa), indicating ice formation damaging pore structure. After freeze at -20 °C, rice straw was further hydrothermally treated at 190 °C with 0.4 M Na2CO3, achieving 72.0 % lignin removal and 97.2 % cellulose recovery. Glucose yield rose to 91.1 % by 4.3 times after 24 h hydrolysis at 10 FPU loading of Cellic®CTec2 cellulase. The specific surface area of rice straw was 2.6 m2/g increased by 1.2 times after freeze. Freeze combined with alkaline-hydrothermal treatment is a green and energy-efficient method for improving enzymatic hydrolysis.

Establishment of low-cost production platforms of polyhydroxyalkanoate bioplastics from Halomonas cupida J9

Microbial production of polyhydroxyalkanoate (PHA) is greatly restricted by high production cost arising from high-temperature sterilization and expensive carbon sources. In this study, a low-cost PHA production platform was established from Halomonas cupida J9. First, a marker-less genome-editing system was developed in H. cupida J9. Subsequently, H. cupida J9 was engineered to efficiently utilize xylose for PHA biosynthesis by introducing a new xylose metabolism module and blocking xylonate production. The engineered strain J9UΔxylD-P8xylA has the highest PHA yield (2.81 g/L) obtained by Halomonas with xylose as the sole carbon source so far. This is the first report on the production of short- and medium-chain-length (SCL-co-MCL) PHA from xylose by Halomonas. Interestingly, J9UΔxylD-P8xylA was capable of efficiently utilizing glucose and xylose as co-carbon sources for PHA production. Furthermore, fed-batch fermentation of J9UΔxylD-P8xylA coupled to a glucose/xylose co-feeding strategy reached up to 12.57 g/L PHA in a 5-L bioreactor under open and unsterile condition. Utilization of corn straw hydrolysate as the carbon source by J9UΔxylD-P8xylA reached 7.0 g/L cell dry weight (CDW) and 2.45 g/L PHA in an open fermentation. In summary, unsterile production in combination with inexpensive feedstock highlights the potential of the engineered strain for the low-cost production of PHA from lignocellulose-rich agriculture waste.

Sequential Process of Subcritical Water Hydrolysis and Hydrothermal Liquefaction of Butia Capitata Endocarp to Obtain Fermentable Sugars, Platform Chemicals, Bio-oil, and Biochar

Butia capitata endocarp (BCE) is a biomass residue with the potential to produce a wide variety of bio-products. The processing of BCE in a sequential process of subcritical water hydrolysis (SWH) and hydrothermal liquefaction (HTL) was investigated to obtain fermentable sugars, platform chemicals, bio-oil, and biochar. The SWH was evaluated at 230 and 260 °C and solvent: feed mass ratios (R) of 10 and 20 for the production of fermentable sugars and platform chemicals. The solid residue from SWH was sequentially submitted to the HTL at 330 and 360 °C for bio-oil and biochar production. The results were analyzed by comparing the sequential (SWH/HTL) and individual (HTL only) processes. The highest yields of fermentable sugars (5.26 g/ 100 g BCE) were obtained for SWH at 260 °C and R-20 with higher contents of xylose (2.64 g/100 g BCE) and cellobiose (1.75 g/100 g BCE). The highest yields of platform chemicals (2.44 g/100 g BCE) were obtained for SWH at 260 °C and R-10 with higher contents of acetic acid (1.78 g/100 g BCE) and furfural (0.54 g/100 g BCE). The highest yield of bio-oil (25.30 g/100 g BCE) occurred in HTL individual process at 360 °C and R-20. Sequential process SWH/HTL showed a decrease in bio-oil yield but maintained a similar biochar yield compared to HTL, in addition to the production of fermentable sugars and platform chemicals.

Integral multi-valorization of agro-industrial wastes: A review

Agriculture and industries related to the agriculture sector generate a large amount of waste each year. These wastes are usually burned or dumped, causing damage to the environment, the economy and society. Due to their composition, they have great potential for obtaining high value-added products in biorefineries. This fact, added to the growing demand for energy and chemicals from fossil resources, is driving the interest of the scientific community in them. Biorefinery processes are hardly profitable when applied individually, so a better alternative is to develop integrated multi-feedstock and multi-product biorefinery schemes using all biomass fractions in a zero-waste approach. However, for industrial scale application, extensive research, scale-up studies, and techno-economic and environmental feasibility analyses are needed. This review compiles information on integrated multi-biorefinery processes from agro-industrial wastes to shed light on the path towards sustainable development and circular bioeconomy.

Barriers to commercial deployment of biorefineries: A multi-faceted review of obstacles across the innovation chain

Realizing integrated biorefineries producing multiple fuels, chemicals and materials from sustainable biomass feedstocks holds promise for transitioning industries onto low-carbon trajectories. However, widespread commercial implementation remains elusive despite two decades of technological advancements. This review synthesizes current literature to provide a comprehensive analysis of key multi-dimensional barriers inhibiting the scale-up of biorefineries. The review discusses the technical challenges around biomass conversion processes. Economic viability concerns such as high capital costs and lack of market competitiveness are also assessed. The review also evaluates the regulatory and policy complexities that poses risks and uncertainties in the scaling up of biorefineries. Socio-political acceptance hurdles including community engagement and public perception are also reviewed. The interconnected nature of these challenges is emphasized and strategies are recommended to enable full potential realization, covering areas such as enhanced stakeholder collaboration, advanced process intensification, supportive policy frameworks, innovative financing models and strategic marketing initiatives. International pilots and cross-sectoral knowledge exchange are highlighted as priority enablers. In conclusion, this review synthesizes insights from extensive demonstration efforts to identify priorities and pathways for accelerating the global commercial transition towards sustainable biorefinery implementation. It aims to inform strategic decision-making and collaborative actions amongst stakeholders in research, industry and policy domains.

Ectopic Production of 3,4-Dihydroxybenzoate in Planta Affects Cellulose Structure and Organization

Lignocellulosic biomass is a highly sustainable and largely carbon dioxide neutral feedstock for the production of biofuels and advanced biomaterials. Although thermochemical pretreatment is typically used to increase the efficiency of cell wall deconstruction, genetic engineering of the major plant cell wall polymers, especially lignin, has shown promise as an alternative approach to reduce biomass recalcitrance. Poplar trees with reduced lignin content and altered composition were previously developed by overexpressing bacterial 3-dehydroshikimate dehydratase (QsuB) enzyme to divert carbon flux from the shikimate pathway. In this work, three transgenic poplar lines with increasing QsuB expression levels and different lignin contents were studied using small-angle neutron scattering (SANS) and wide-angle X-ray scattering (WAXS). SANS showed that although the cellulose microfibril cross-sectional dimension remained unchanged, the ordered organization of the microfibrils progressively decreased with increased QsuB expression. This was correlated with decreasing total lignin content in the QsuB lines. WAXS showed that the crystallite dimensions of cellulose microfibrils transverse to the growth direction were not affected by the QsuB expression, but the crystallite dimensions parallel to the growth direction were decreased by ∼20%. Cellulose crystallinity was also decreased with increased QsuB expression, which could be related to high levels of 3,4-dihydroxybenzoate, the product of QsuB expression, disrupting microfibril crystallization. In addition, the cellulose microfibril orientation angle showed a bimodal distribution at higher QsuB expression levels. Overall, this study provides new structural insights into the impact of ectopic synthesis of small-molecule metabolites on cellulose organization and structure that can be used for future efforts aimed at reducing biomass recalcitrance.

A Multiomics Perspective on Plant Cell Wall-Degrading Enzyme Production: Insights from the Unexploited Fungus Trichoderma erinaceum

Trichoderma erinaceum is a filamentous fungus that was isolated from decaying sugarcane straw at a Brazilian ethanol biorefinery. This fungus shows potential as a source of plant cell wall-degrading enzymes (PCWDEs). In this study, we conducted a comprehensive multiomics investigation of T. erinaceum to gain insights into its enzymatic capabilities and genetic makeup. Firstly, we performed genome sequencing and assembly, which resulted in the identification of 10,942 genes in the T. erinaceum genome. We then conducted transcriptomics and secretome analyses to map the gene expression patterns and identify the enzymes produced by T. erinaceum in the presence of different substrates such as glucose, microcrystalline cellulose, pretreated sugarcane straw, and pretreated energy cane bagasse. Our analyses revealed that T. erinaceum highly expresses genes directly related to lignocellulose degradation when grown on pretreated energy cane and sugarcane substrates. Furthermore, our secretome analysis identified 35 carbohydrate-active enzymes, primarily PCWDEs. To further explore the enzymatic capabilities of T. erinaceum, we selected a β-glucosidase from the secretome data for recombinant production in a fungal strain. The recombinant enzyme demonstrated superior performance in degrading cellobiose and laminaribiose compared to a well-known enzyme derived from Trichoderma reesei. Overall, this comprehensive study provides valuable insights into both the genetic patterns of T. erinaceum and its potential for lignocellulose degradation and enzyme production. The obtained genomic data can serve as an important resource for future genetic engineering efforts aimed at optimizing enzyme production from this fungus.

A review of nanotechnology in enzyme cascade to address challenges in pre-treating biomass

Nanotechnology has become a revolutionary technique for improving the preliminary treatment of lignocellulosic biomass in the production of biofuels. Traditional methods of pre-treatment have encountered difficulties in effectively degrading the intricate lignocellulosic composition, thereby impeding the conversion of biomass into fermentable sugars. Nanotechnology has enabled the development of enzyme cascade processes that present a potential solution for addressing the limitations. The focus of this review article is to delve into the utilization of nanotechnology in the pretreatment of lignocellulosic biomass through enzyme cascade processes. The review commences with an analysis of the composition and structure of lignocellulosic biomass, followed by a discussion on the drawbacks associated with conventional pre-treatment techniques. The subsequent analysis explores the importance of efficient pre-treatment methods in the context of biofuel production. We thoroughly investigate the utilization of nanotechnology in the pre-treatment of enzyme cascades across three distinct sections. Nanomaterials for enzyme immobilization, enhanced enzyme stability and activity through nanotechnology, and nanocarriers for controlled enzyme delivery. Moreover, the techniques used to analyse nanomaterials and the interactions between enzymes and nanomaterials are introduced. This review emphasizes the significance of comprehending the mechanisms underlying the synergy between nanotechnology and enzymes establishing sustainable and environmentally friendly nanotechnology applications.