Search Results (206)

Biorefineries that convert the organic fraction of municipal solid waste (OFMSW) into advanced biofuels can integrate waste management with renewable energy production. However, their environmental performance remains insufficiently characterised owing to a scarcity of life cycle assessment (LCA) studies based on real operational data. This study presents a gate-to-gate LCA of a demonstration biorefinery processing source-separated food waste into bio-oils, bioethanol, and biogas. The ReCiPe 2016 Midpoint (H) method was applied across 18 impact categories, with system expansion crediting the displacement of rapeseed oil, maize-derived ethanol, and marginal biogas-derived electricity. The net global warming potential (GWP) was 68.5 kg CO₂ eq per tonne of wet OFMSW (69% reduction from gross), placing the biorefinery 83–93% below landfilling, 63% below incineration with CHP, and above standalone anaerobic digestion systems that lack the energy-intensive drying and enzymatic hydrolysis steps of the present configuration. Bio-oil and bioethanol achieved net-negative GWP per kilogram of product (−0.89 and −0.66 kg CO₂ eq, respectively), whilst eleven of eighteen categories achieved net savings under system expansion. Enzyme production dominated the bioethanol environmental profile (37–94% across categories), whilst drying dominated bio-oil (46–93%). Monte Carlo simulation confirmed that the sign of the net impact stayed unchanged across the entire 95% confidence interval (the interval did not span zero) for 17 of 18 categories. Full article

Agricultural waste valorization offers a sustainable route for developing advanced materials for renewable energy applications. In this study, cellulose nanocrystals (CNCs) were extracted from melon agricultural residues through hydrochloric, sulfuric, and phosphoric acid hydrolysis and incorporated into a poly(vinyl alcohol) (PVA) matrix to fabricate proton exchange membranes for potential applications in glucose biofuel cells. The influence of CNC surface chemistry on membrane morphology, crystallinity, thermal stability, mechanical properties, proton conductivity, and glucose permeability was systematically investigated. CNC incorporation improved membrane compactness, crystallinity, and physicochemical stability compared with neat PVA. Among the developed membranes, PVA/CNC-S exhibited the best overall performance, showing the highest proton conductivity (1.032 × 10⁻² mS·cm⁻¹ at 50 °C) and the lowest glucose permeability (3.25 × 10⁻⁹$\pm 0.15$ cm²·s⁻¹). Furthermore, the composite membranes exhibited enhanced thermal and oxidative stability due to strong intermolecular interactions between PVA and functionalized CNCs. The results reveal that CNC surface chemistry plays a crucial role in regulating membrane transport properties and structural organization. In particular, sulfate-functionalized CNCs improved proton transport while minimizing glucose crossover. These findings highlight the potential of agricultural waste-derived PVA/CNC membranes as sustainable, low-cost, and efficient proton exchange membranes for potential applications in glucose biofuel cells and related bioelectrochemical energy systems. Full article

Xylanases catalyze the hydrolysis of β-1,4-xylosidic linkages in xylan, a major component of plant cell walls, and are widely used in the food, feed, pulp and paper, and biofuel industries. GH11 xylanase from the hemicellulose-degrading bacterium Thermoanaerobacterium saccharolyticum (TsaGH11) exhibits high catalytic activity, making it an attractive enzyme for industrial applications. The flexibility of the thumb domain of TsaGH11 has been investigated under cryogenic and room temperature conditions; however, the substrate recognition mechanism of TsaGH11 at the optimal temperature is unknown. To better understand the molecular mechanism of substrate recognition, the high-resolution crystal structure of TsaGH11 was determined at 1.4 Å resolution. All-atom molecular dynamics simulations at 300, 320, 340, and 360 K revealed that increasing the temperature induced fluctuations in the substrate-recognizing thumb domain. At an optimal temperature of 340 K, the substrate-binding cleft of TsaGH11 predominantly adopted a closed conformation. However, the thumb domain exhibited larger fluctuations at 340 K than at other temperatures, sampling both open and closed conformations, suggesting that substrate recognition in TsaGH11 proceeds through a conformational selection-like mechanism. At 360 K, TsaGH11 unfolded partially at a site opposite the substrate-binding cleft, providing potential targets for protein engineering to improve its thermostability for industrial applications. These findings provide a better understanding of the molecular mechanism of TsaGH11 and offer valuable guidance for the rational engineering of GH11 xylanases for industrial applications. Full article

The introduction of sustainable practices into waste management can have a favorable environmental impact, increase resource value, and yield economic gains. Hydrothermal technologies have strong potential for the production of up-cycled ingredients from biowaste (amino acids, sugars, phenols, pharmacologically active compounds, etc.), enabling high energy recovery (50–80%) from biowaste with net-negative carbon emissions. This review discusses the use of subcritical and supercritical water technologies for sustainable valorization of biowaste and conversion of biomass into high-value chemicals and biofuels. The potential for the extraction/generation of bioactive compounds from plant and animal waste is presented, emphasizing the efficiency, compound stability, and bioactivity of the fractions obtained. The possibilities of simultaneous extraction of added-value compounds and hydrolysis of feedstock biopolymers by these technologies are elaborated. The review further addresses the production of biofuels through hydrothermal carbonization for solid fuels, hydrothermal waste liquefaction for liquid fuels, and supercritical water gasification for gaseous fuels. The paper highlights the environmental and economic advantages of technologies based on sub- and supercritical water over conventional chemical and fermentative routes, emphasizing their contribution to a circular bioeconomy by converting biowaste into value-added products and sustainable energy sources. Full article

Lignocellulosic wastes are low-carbon, renewable and sustainable feedstocks for replacing fossil fuels in the production of energy and chemical products. However, the bioconversion of lignocellulose into biofuels or biochemicals is costly. To address the high cost, this study extracted essential oil (EO) from ginger stalks and leaves (GSL) as an antioxidant to valorize the bioconversion process of GSL. The Box–Behnken design was used to optimize EO extraction, and the maximum EO yield of 2.99% was obtained under the optimal condition of KOH infiltration for 26 h, extraction for 3 h, and an n-hexane-to-GSL ratio of 8 (v/w). With 95% n-hexane recovery and no generation of waste liquid during the extraction process, fugitive emissions and solvent waste were reduced, enhancing sustainability. The EO’s antioxidant activity exceeded that of commercial ginger EO. The combined process of KOH infiltration and n-hexane extraction induced physicochemical changes in GSL and improved its enzymatic hydrolysis efficiency from 2.70% to 69.09%. According to the economic assessment, the bioconversion of GSL into bioethanol would benefit from the EO product, with the on-site production cost of cellulase being no more than 0.98 USD/kg. This study presents a feasible and sustainable case for lignocellulosic biorefining. Full article

To establish a biorefinery within kraft-pulp mills, the extraction of fermentable sugars must be balanced with the preservation of fiber quality for papermaking. This study investigates this trade-off by applying partial enzymatic hydrolysis to unbleached high-kappa eucalyptus kraft pulp to co-produce bioethanol and packaging-grade materials. Although the mass-transfer limitations inherent to the high-consistency strategy (15% solids or 150 g L⁻¹) restrict extensive saccharification (keeping glucose conversion below 5% at 1.5 h), it naturally directs the process toward a low-severity regime essential for fiber conservation. Structural analysis (X-ray diffraction and microscopy) revealed that enzymes preferentially targeted amorphous regions, increasing crystallinity (from ≈74% to ≈82%) but reducing intrinsic fiber strength (tear) over time (dropping from ~5.6 to ~2.3 mN·m²·g⁻¹ within 30 min). However, a strategic window for valorization has been identified. Instead of direct papermaking, hydrolyzed residue is highly effective as a strength-enhancing additive. When blended (20% w w⁻¹) with commercial pulp, the modified fibers improved interfiber bonding, restored the tensile strength, and significantly increased the Burst Index (up to ~1.7 kPa·m²·g⁻¹). These results demonstrate a viable industrial approach using partial hydrolysis to recover hemicellulose-based sugars for biofuels, while transforming the solid fraction into a high-performance reinforcement agent for paper packaging. This approach effectively converts a potential trade-off into a synergistic dual-product stream. Full article

Growing global energy demand and concerns over climate change and fossil fuel depletion have increased interest in sustainable bioproducts such as ethanol. Unlike first-generation (1G) ethanol derived from food crops (e.g., corn), second-generation (2G) ethanol is produced from lignocellulosic biomass, an abundant non-food resource that addresses key sustainability concerns. Consolidated bioprocessing (CBP) integrates enzyme production, hydrolysis, and fermentation into a single step, using either microbial consortia or engineered microorganisms, thereby simplifying the process and potentially reducing costs compared with separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF). However, CBP systems are complex due to dynamic interactions among microbial communities, metabolic pathways, and process conditions. Addressing this complexity requires modeling approaches that capture nonlinear relationships and support robust process optimization. Machine learning (ML)-based models offer data-driven tools to represent complex bioprocess dynamics, improve predictive accuracy, and optimize bioproduct formation, thereby supporting progress toward commercial viability. Although CBP can be applied to a range of bioproducts, this review primarily focuses on lignocellulosic ethanol and closely related biofuels. The review provides a comprehensive overview of key CBP processes, the current state of CBP modeling, major limitations, and the emerging role of ML in addressing modeling challenges. It summarizes recent modeling techniques for CBP, including polynomial models and response surface methodologies, and discusses regression and neural network approaches in detail. Both first-principles and data-driven modeling strategies are considered, highlighting advances that can improve the scalability and efficiency of CBP for bioproduction. Overall, this review offers perspectives on modeling-enabled pathways for utilizing low-cost lignocellulosic biomass in sustainable bioprocessing. Full article

This study evaluated the potential of sawdust as an inducer of carbon for the production of lignocellulolytic (cellulase and xylanase) enzymes by filamentous fungi for biofuel applications. Fourteen soil samples were collected from a phosphate mine in Phalaborwa, South Africa. Filamentous fungi were isolated from these samples using cellulose and xylose media. These isolateswere tested qualitatively and quantitatively for endocellulase and xylanases. Four isolates were found to have promising xylanase activity and these were identified as Amesia atrobrunnea, Penicillium citrinum, Rhizopus azygosporus and Aspergillus quadrilineatus using ITS1/2 sequencing. A time-course assay for xylanase activity revealed that R. azygosporus and A. quadrilineatus exhibited the highest activity. The crude enzymes were extracted from these strains and used for the enzymatic saccharification of the untreated sawdust. The total reducing sugars were estimated using the DNS method. The results for the enzymatic saccharification showed that a high total reducing sugar concentration of 2.35 g/L was released by 20 U/g of crude xylanases from A. quadrilineatus after 60 h of hydrolysis, while the synergistic hydrolysis of sawdust with the commercial cellulase, Celic CTec2, and the crude enzyme of 6 U/g from A. quadrilineatus showed the maximum concentration of total reducing sugars of 1.41 g/L after 72 h. Sawdust proved to be an effective inducer of xylanase production, although it was less effective for cellulase. This study reports that the commercial cellulase was outperformed by the crude enzymes during hydrolysis, highlighting the possibility that commercial enzymes may be replaced by microbial enzymes, thus lowering the environmental hazards of chemical formulations. Sugar yields could potentially be improved through biomass pretreatment, enzyme purification and strain improvement. Full article

The effective utilization of biomass components in the pre-hydrolysis liquor (PHL) of lignocellulose is a crucial way for traditional pulp and paper mills converting into biomass refining facilities. In the present work, separation technologies are summarized and reviewed—including acidification, ethanol precipitation, flocculation and coagulation, adsorption, solvent extraction, enzyme treatment, and oxidation—with regard to component separation and impurity removal. The utilization of hemicelluloses from PHL for the production of furfural, adhesive and biofuel, as well as the application of lignin separated from PHL and the full components utilization of PHL without separation is reviewed and analyzed. Full article

Esterases catalyze the hydrolysis and transesterification of short-chain fatty acid esters, and microbial esterases are used in the production of biofuels, cosmetics, food, and pharmaceuticals. The soil strain Bacillus paralicheniformis T7 secretes enzymes with esterase activity; however, many bacterial enzymes remain insufficiently studied. Therefore, this study aimed to identify and characterize novel GDSL esterases produced by B. paralicheniformis. Protein mass spectrometry, combined with proteomics and genomics, identified genes encoding two GDSL esterases, which were cloned into the pET-28c(+) vector. The resulting proteins were obtained in Escherichia coli BL21(DE3) as the recombinant esterases rEST-24 and rEST-28. These recombinant GDSL esterases showed maximum activity at 40 °C and pH 7.0. Moreover, Ca²⁺, Zn²⁺, Cu²⁺, and Fe²⁺ ions inhibited their activity, and rEST-28 was resistant to the detergents Tween-20, Tween-80, and Triton X-100. High-yield esterase activity was detected in bacteria cultured on feather medium and nutrient broth, and submerged fermentation of the B. paralicheniformis T7 strain on feather medium enabled the production of an esterase extract exhibiting activity of 17,618 ± 610 U/g. These results suggest that the B. paralicheniformis T7 strain can produce esterases and shows promising potential for application in technologies that degrade fatty acid esters using hydrolytic enzymes. Full article

Alkaline pretreatment of wheat straw could significantly augment enzymatic hydrolysis for producing fermentable sugars, which is a pivotal process for the conversion of lignocellulosic biomass into advanced biofuels, biomaterials, or biochemicals. Yet, the enzymatic conversion process system is complex and multivariate, and study on the interaction mechanism of the key parameters in enzymatic hydrolysis is still lacking. Therefore, in this work, multivariate data analysis (MDA) (i.e., principal component analysis (PCA) and partial least square (PLS)) was conducted to reveal the inherent relationship and the significance of these factors in a modified alkali pretreatment system. A robust model, developed from 140 enzymatic hydrolysis datasets, was validated with an additional 20 datasets, demonstrating the predictive prowess of the PLS model. MDA identified that cellulase dosage, mechanical refining, dye adsorption value, and solid content were paramount variables. The integration of cellulase and xylanase notably elevated sugar yields and the conversion rates of carbohydrates, surpassing those of single enzyme treatments. The model’s predictive accuracy, reflected in the close alignment between observed and predicted data, underscores its suitability for optimizing and controlling the enzymatic hydrolysis process. This study paves a way for data-driven strategies to enhance industrial bioprocessing of lignocellulosic feedstocks. Full article

The continuous fossil fuel exhaustion, as well as the increasing environmental challenges that are occurring globally, has underscored the need for research on alternative pathways of producing biofuels that will minimize aviation emissions over the next decades. The present review explores the employment of diverse waste sources as feedstock and enzymes as catalysts as environmentally friendly methods for producing sustainable aviation fuels (SAF). To achieve this goal, a comprehensive review was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. The results demonstrated that waste feedstocks catalyzed by enzymes represent an innovative alternative for SAF production. Specifically, the combination of enzymatic hydrolysis and microbial fermentation demonstrated considerable effectiveness in transforming complex waste feedstocks, such as lignocellulosic biomass, municipal solid waste, and food waste, into SAF precursors, including bio-isobutene and fatty acid methyl esters. Moreover, employing Chlorella variabilis fatty acid photodecarboxylase enzymes for photoenzymatic decarboxylation demonstrated significant conversion efficiency, particularly under gentle conditions, low energy consumption and remarkable selectivity. However, further research and development of the reviewed methods are necessary to enable the industrialization of these technologies. Full article

The conversion of lignocellulosic biomass into high-value fermentation products generates a lignin-rich hydrolysis residue (LRR), which is predominantly combusted for process heat, offering limited valorization potential. This study investigates the hydrothermal carbonization (HTC) of this residue derived from forest residue biomass (FRB) to produce high-energy-density hydrochar. HTC, a thermochemical conversion process conducted in the presence of water, enables direct processing of wet lignin-rich residues without the need for drying or solvent-based lignin extraction or purification, thereby reducing costs and complexity. Experiments were conducted at 200–280 °C, with a fixed reaction time of 1 h, and the resulting hydrochars were thoroughly characterized for their chemical composition, structural morphology, and thermal behavior. Thermogravimetric analysis confirmed improved pyrolysis properties of the HTC products. Hydrochar yield decreased by 26.26% as the temperature increased from 200 to 280 °C, accompanied by marked improvements in fuel quality. The maximum higher heating value, observed at 280 °C, was 1.75 times greater than that of raw LRR. Elemental analysis and a Van Krevelen evaluation confirmed enhanced carbonization, as evidenced by increasing carbon content and decreasing oxygen content. The specific surface area peaked at 2.66 m²/g at 200 °C before declining with further temperature increases. This study demonstrates a sustainable pathway for valorization of lignin-rich residues from lignocellulosic biorefineries into solid biofuels, advancing circular bioeconomy and offering insights into using HTC for energy and environmental applications. Full article

The global demand for sustainable energy has accelerated the development of biofuels, aiming to reduce fossil fuel reliance and environmental impact. Second-generation ethanol (2G), produced from lignocellulosic biomass such as sugarcane bagasse and straw, is a promising alternative aligned with the circular economy. Its production relies on pretreatments to improve the enzymatic access to polysaccharides. Among the available methods, the organosolv (O) and hydrothermal (H) pretreatments are effective in separating the biomass into cellulose-rich pulps and hemicellulosic liquors. In this study, these pretreatments were applied to sugarcane bagasse (SCB) and straw (SS), aiming to obtain hemicellulosic fractions for bioconversion. The characterization of pretreated biomasses showed increased cellulose content, indicating successful delignification. After the lignin precipitation, the hemicellulosic liquors were submitted to enzymatic hydrolysis, with increases in the total reducing sugar (TRS) concentrations, from 11.144 to 13.440 g·L⁻¹ (SBO), 16.507 to 22.492 g·L⁻¹ (SBH), 8.560 to 9.478 g·L⁻¹ (SSO), and 14.164 to 22.830 g·L⁻¹ (SSH), with highlights for the hydrothermal pretreated hydrolysates in the improvement of sugar release. HPLC confirmed these gains, notably in the xylose content. The results indicated the potential of hemicellulosic liquors for the fermentation of pentoses, supporting integrated bioethanol production. This approach promotes the efficient use of agro-residues and strengthens the role of biofuels in low-carbon and sustainable energy systems. Full article

There is an increasing industrial demand for sustainable resources for lipid-based biofuels and platform chemical production. A promising, CO₂-efficient resource is autotrophically cultivated microalgae, either for direct single-cell oil (SCO) production or as a biomass substrate for fermentative SCO production via organisms like yeasts. Regarding the latter, chemical biomass hydrolysis typically results in high sugar yield and high salt concentrations due to the required neutralization prior to fermentation. In contrast, enzymatic hydrolysis is often lacking in mass efficiency. In this study, the enzymatic hydrolysis of both nutrient-replete and lipid-rich autotrophic Microchloropsis salina biomass was optimized, testing different pre-treatments and enzyme activities. Hereby, the protease treatment to weaken the cell wall integrity and the dosing of the Cellic CTec3 was identified to have the highest effect on hydrolysis efficiency. Sugar yields of 63% (nutrient-replete) and almost 100% (lipid-rich) could be achieved. The process was successfully scaled-up in mini bioreactors at a 250 mL scale. The resulting hydrolysate of the lipid-rich biomass was tested as a substrate of the oleaginous yeast Cutaneotrichosporon oleaginosus in a consumption-based acetic acid fed-batch setup. It outperformed both the model substrate and the glucose control, demonstrating the high potential of the hydrolysate as feedstock for yeast oil production. The presented sequential and circular SCO-producing value chain highlights the potential for mass- and space–time-efficient biofuel production, combining the autotrophic cultivation of oleaginous algae with decoupled yeast oil fermentation for the first time. Full article