Search Results (237)

The transition to sustainable energy sources has intensified interest in lignocellulosic biomass (LCB) as a feedstock for second-generation biofuels. However, the inherent structural recalcitrance of LCB requires the utilization of an effective pretreatment to enhance enzymatic hydrolysis and subsequent fermentation yields. This manuscript presents a novel, single-step, and optimized nitrogen explosive decompression system (NED 3.0) designed to address the critical limitations of earlier NED versions by enabling the in situ removal of inhibitory compounds from biomass slurry and fermentation inefficiency at elevated temperatures, thereby reducing or eliminating the need for post-treatment detoxification. Aspen wood (Populus tremula) was pretreated by NED 3.0 at 200 °C, followed by enzymatic hydrolysis and fermentation. The analytical results confirmed substantial reductions in common fermentation inhibitors, such as acetic acid (up to 2.18 g/100 g dry biomass) and furfural (0.18 g/100 g dry biomass), during early filtrate recovery. Hydrolysate analysis revealed a glucose yield of 26.41 g/100 g dry biomass, corresponding to a hydrolysis efficiency of 41.3%. Fermentation yielded up to 8.05 g ethanol/100 g dry biomass and achieved a fermentation efficiency of 59.8%. Inhibitor concentrations in both hydrolysate and fermentation broth remained within tolerable limits, allowing for effective glucose release and sustained fermentation performance. Compared with earlier NED configurations, the optimized system improved sugar recovery and ethanol production. These findings confirm the operational advantages of NED 3.0, including reduced inhibitory stress, simplified process integration, and chemical-free operation, underscoring its potential for scalability in line with the EU Green Deal for bioethanol production from woody biomass. Full article

Beer production produces significant amounts of brewers’ spent grain (BSG), a lignocellulosic by-product with important environmental and economic impacts. Despite its high moisture content and rapid microbial breakdown, BSG has a stable, nutrient-rich composition, especially high in protein, fiber, and polyphenolic compounds. While its perishability limits direct use in food systems, BSG is often repurposed as livestock feed. Recent advances in bioprocessing and extraction technologies have expanded their use across different sectors. This review explores the composition of crude BSG and evaluates innovative valorization methods, including recovering bioactive compounds with pharmaceutical and nutraceutical value, and converting them into biofuels such as biogas, biodiesel, and bioethanol. Special focus is given to methods involving enzymatic hydrolysis, fermentation, and chemical extraction to isolate proteins, peptides, amino acids, sugars, and polyphenols. By analyzing emerging applications and industrial scalability challenges, this review highlights BSG’s growing role within circular economy models and its potential to promote sustainable innovations in both the brewing industry and the wider bioeconomy. Full article

The presence of various inhibitory compounds in lignocellulosic hydrolysates poses a significant challenge for bioethanol production, requiring yeasts with exceptional multistress tolerance. This study introduces the novel application and demonstrates the robust performance of the nonconventional yeast Saccharomycodes ludwigii APRE2 for efficient bioethanol production directly from undetoxified sugarcane bagasse hydrolysate (SBH) at 37 °C. This approach critically eliminates the need for the costly detoxification pretreatments often required in industrial processes. Initial experiments confirmed S. ludwigii APRE2’s capability to ferment undetoxified SBH. To optimize fermentation efficiency, a central composite design (CCD) approach was implemented. This statistical method identified the following precise optimal parameters: sugar concentration (143.95 g/L), diammonium phosphate (4.99 g/L), pH (4.98), yeast extract (8.94 g/L), and magnesium sulfate (2.22 g/L). Under these optimized conditions, impressive results were achieved: a maximum ethanol concentration of 38.11 g/L, productivity of 1.59 g/L·h, and yield of 0.45 g/g. Notably, the ethanol productivity and theoretical yield achieved by S. ludwigii APRE2 using this inhibitor-rich, undetoxified SBH (containing acetic acid, formic acid, furfural, and 5-(hydroxymethyl)furfural) were superior to those previously reported for other ethanologenic yeasts under similar challenging conditions. This research establishes S. ludwigii APRE2 as a highly promising and industrially viable candidate for sustainable bioethanol production from lignocellulosic biomass, with its key novelty being its superior performance on undetoxified feedstocks, potentially reducing overall production costs. Full article

After a brief characterisation of lignocellulosic biomass (LCB) in terms of its biochemical structure and the pretreatment techniques used to disrupt lignin structure and decrystallise and depolymerise cellulose, this review considers five main pathways for biochemical biomass conversion: starting with anaerobic digestion to convert various LCB feedstocks into bioproducts; considering the integration of biochemical and thermochemical processes, syngas fermentation, which has been recently developed for biofuel and chemical production, is reviewed; the production of 2G bioethanol and biobutanol from LCB waste is discussed; the literature on biohydrogen production by dark fermentation, photofermentation, and bioelectrochemical processes using microbial electrolysis cells as well as hybrid biological processes is reviewed. The conclusions and future prospects of integrating biochemical and thermochemical conversion processes of biomass are discussed and emphasised. Full article

Lignocellulosic biomass, derived from plant materials, represents a renewable alternative to fossil fuels and plays a crucial role in advancing environmental sustainability. This systematic review investigates recent developments in the conversion of lignocellulosic biomass into biofuels, with a focus on pre-treatment technologies that enhance enzymatic hydrolysis, a critical step in efficient biofuel production. This review addresses two primary questions: (1) What are the most effective pre-treatment methods for enhancing enzymatic hydrolysis in lignocellulosic biomass conversion? (2) How do these pre-treatment methods compare in terms of efficiency, environmental impact, and economic feasibility? Consequently, studies were selected based on inclusion criteria that focus on research investigating these pre-treatment methods and their comparative performance. A structured search of original studies was applied across databases such as Crossref, Google Scholar, Scopus, PubMed, and Semantic Scholar, resulting in the inclusion of 17 peer-reviewed articles published between 2019 and 2024. The findings highlight effective pre-treatment methods that significantly improve enzymatic accessibility and bioethanol yields. However, ongoing challenges such as feedstock variability, process efficiency, and cost-effectiveness remain. These results highlight the need for further research and development to optimize conversion technologies and identify new areas for exploration. Full article

Various pretreatment methods, often employed in wood biorefineries, aim to disrupt the wood architecture, thereby enhancing the efficiency of hemicellulose extraction for increasing the production of bio-ethanol, bio-gas, and bio-oil, as well as improving the pulping process. Pretreatment for the pulping process has advantages such as enhanced yield in biorefined products and reducing chemicals and energy consumption. This study examined the effect of an alkaline hydrolysis of birch sawdust on the chemical composition, aggregation ability, and surface activity of soda lignin obtained by soda pulping. The alkaline hydrolysis of birch sawdust led to a remarkable removal of hemicellulose and reduced its mechanical strength. The resorption of lignin fragments on the lignocellulosic matrix during the hydrolysis was observed. The soda pulping of the original and the treated sawdust was carried out under laboratory conditions at 165 °C for 90 min, using 4.5% sodium hydroxide. A higher yield of soda lignin and pulp was obtained from the treated sawdust. The reduced content of acidic and methoxyl groups in the chemical composition of the soda lignin from the hydrolyzed sawdust was explained by the predominance of polycondensation reactions in forming its primary structure. The changes in size and zeta potential values of the formed lignin particles, as well as in the modality of the size distribution with decreasing pH, were studied. The early-proposed suggestion about the existence of structural complementarity in the formation of the ordered lignin supermolecular structures has been testified. The higher surface activity at the air–water interface for the soda lignin extracted from the hydrolyzed sawdust, compared to the lignin from the original residue, was mainly attributed to a lower content of the acidic groups in its chemical composition, shifting the hydrophilic–hydrophobic balance of its structure toward hydrophobicity. Full article

Efficient co-fermentation of glucose and xylose remains a critical hurdle in second-generation bioethanol production. In this study, we evaluated two non-Saccharomyces yeasts—Wickerhamomyces anomalus UEMG-LF-Y2 and Diutina rugosa UEMG-LF-Y4—under mixed-sugar conditions. D. rugosa exhibited superior xylose metabolism and ethanol productivity, achieving a maximum volumetric productivity (Q_P) of 0.55 g/L·h in a medium containing 20 g/L glucose and 40 g/L xylose. Its highest ethanol yield (Y_P/S) reached 0.45 g EtOH/g sugar, comparable to results from engineered Saccharomyces cerevisiae strains. By contrast, W. anomalus displayed lower ethanol yields (0.24–0.34 g/g) and greater sensitivity to catabolite repression induced by 2-deoxyglucose (2-DG). Xylose consumption by D. rugosa exceeded 80% in high-xylose media, while W. anomalus left residual xylose under all tested conditions. A strong inverse correlation (r < −0.98) between ethanol accumulation and xylose uptake was observed, especially for W. anomalus, indicating ethanol-induced inhibition as a key challenge. These findings highlight the potential of D. rugosa as a robust non-Saccharomyces platform for lignocellulosic bioethanol processes, whereas W. anomalus may benefit from further metabolic or process optimizations. Future research should address ethanol tolerance, inhibitory byproducts, and large-scale feasibility to fully exploit these strains for second-generation bioethanol production. Full article

This study assesses the sustainability of bioethanol production from multiple agricultural feedstocks, including corn stover, wheat straw, and rice husk, using a life cycle assessment (LCA) method. The process focuses on converting lignocellulose biomass into bioethanol through advanced biotechnology, enriching energy security and supporting sustainable development in Pakistan. The process includes various stages of feedstock utilization, including cultivation, harvesting, transportation, preprocessing, and conversion, eventually yielding 1 kg of bioethanol with different inventories for each of the three feedstocks. A comparative analysis of the three feedstocks reveals that the wheat straw showed the highest environmental impacts, while rice husk exhibits the least environmental impacts and emerges as a more sustainable and viable option for bioethanol production. The economic assessment revealed the feasibility of bioethanol production, achieving a daily revenue of $9600 and a monthly income of $211,200, based on 22 working days in a single 8 h shift. The total initial capital investment cost was estimated at $478,515, while operational costs were calculated at $225,921. The external cost of the plant was evaluated at $14.23. Transitioning from grid-mix to renewable energy, such as photovoltaic systems, showed a reduction among three feedstocks. Therefore, bioethanol production not only addresses waste management challenges but also contributes to waste-to-energy conversion and renewable energy generation, aligning with public health goals and sustainable development. The findings highlight the potential of bioethanol production as a strategic solution to manage agricultural waste sustainably and reduce greenhouse gas emissions. Full article

Interest in the production of bioethanol from inedible biomass is growing worldwide because of its sustainable supply and lack of competition with food supplies. Candida krusei (also known as Pichia kudriavzevii or Issatchenkia orientalis) is one of the most suitable thermotolerant yeasts used in the simultaneous saccharification and fermentation process for bioethanol production. In the production of bioethanol from lignocellulosic biomass as a feedstock, various environmental conditions occur, and the stress tolerance capacity of C. krusei, especially its low pH and tolerance to inhibitors, limits its practical application. In this study, to select a suitable second-generation bioethanol-producing strain, the tolerance capacity of five available C. krusei strains (NBRC0584, NBRC0841, NBRC1162, NBRC1395 and NBRC1664) was characterized. Spot assay and growth experiment results showed that among the five C. krusei strains, C. krusei NBRC1664 showed superior tolerance capacity for low pH and inhibitors. Furthermore, this strain efficiently produced ethanol from glucose under low pH conditions with or without sulfate. A comparative analysis of the draft genome sequences suggested that Opy2, Sln1 and Cdc24 in the HOG pathway are conserved only in C. krusei NBRC1664, which may contribute to its superior tolerance to low pH levels. Moreover, amino acid sequence alignment showed that aldehyde dehydrogenase family proteins, which catalyze the degradation of cyclic aldehydes, are commonly conserved in C. krusei. In addition, the increased transcription levels in C. krusei NBRC1664 could play a role in its higher tolerance to inhibitors. These results suggest that C. krusei NBRC1664 is a more suitable strain for application in industrial processes for second-generation bioethanol production. Full article

This study investigates the effect of hot water extraction (HWE). The research investigates how different biomass fractions (0–4 mm, 4–8 mm, and 8–16 mm) respond to hydrothermal treatment, with cellulose content analyzed using the Kürschner–Hoffer method. Results indicate that cellulose loss varies across fractions, with the highest degradation observed in the 8–16 mm fraction and the lowest in stalks thinner than 4 mm. The HWE process removes both hemicellulose and lignin selectively, which helps improve enzyme accessibility and maximize bioethanol yields. The absence of fermentation inhibitors suggests that HWE is an effective alternative to acid-based pretreatment. Based on these findings, optimizing process parameters for sustainable bioethanol production from hemp biomass may be possible. Optimal HWE conditions and alternate pretreatment methods should be evaluated in future research to maximize efficiency and industrial feasibility. Full article

The effective utilization of nonfood biomass for bioethanol production represents a promising strategy for sustainable energy development. Moreover, limited research has been conducted on broom grass (Thysanolaena latifolia) as a potential feedstock for bioethanol production, particularly regarding the effects of NaOH autoclave pretreatment on its enzymatic digestibility and fermentability. This study optimized sodium hydroxide (NaOH) pretreatment combined with autoclaving to enhance the enzymatic digestibility of broom grass biomass. The effects of NaOH concentration (1–4%) and temperature (110–130 °C) on biomass composition, structural features, and enzymatic hydrolysis were systematically evaluated. Pretreatment with 2% NaOH at 120 °C emerged as optimal, achieving 74.7% lignin removal and 93.2% glucan recovery, thereby significantly improving enzymatic hydrolysis efficiency (88.0%) and glucose recovery (33.3%). Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses revealed that these improvements were attributed to the increased surface porosity and the selective removal of amorphous components while maintaining cellulose crystallinity. The pretreated biomass hydrolysate exhibited excellent bioethanol production. Fermentation using Saccharomyces cerevisiae TISTR 5339 achieved an 86.4% ethanol conversion rate, yielding 147 g of bioethanol per 1000 g of pretreated biomass and representing a 2.6-fold increase compared to untreated feedstock. These findings demonstrate the potential of the NaOH autoclave pretreatment in enhancing bioethanol production from broom grass biomass, aiding the advancement of sustainable and cost-effective lignocellulosic biorefinery processes. The utilization of broom grass for bioethanol production presents an opportunity to valorize this multifaceted plant and expand its potential beyond its traditional uses. Full article

The integrated production of ethanol fuel through the simultaneous use of various by-products and waste materials is an intriguing concept, as it maximizes the raw material potential while addressing the challenge of managing waste biomass from different technological processes. The efficient utilization of lignocellulosic waste depends on employing a pretreatment method that enhances the susceptibility of structural polysaccharides to hydrolysis. The aim of the study was to assess the possibility of the simultaneous use of corn stillage biomass and beet molasses as raw materials for the production of ethanol fuel. The research focused on optimizing the process conditions for the acid pretreatment of stillage biomass and the enzymatic hydrolysis of cellulose and evaluating the effectiveness of two fermentation strategies: SHF (Separate Hydrolysis and Fermentation) and SSF (Simultaneous Saccharification and Fermentation). The highest hydrolysis susceptibility was observed in biomass pretreated with 2% v/v H₃PO₄ for 30 min at 121 °C. The maximum glucose concentration of about 12 g/L (hydrolysis efficiency about 35.5%) was achieved even with the lowest enzyme dose, i.e., 7.5 FPU per gram of biomass. The yeast also showed high fermentation activity in media prepared from stillage biomass and molasses, producing about 50 g/L of ethanol regardless of the fermentation strategy used. The complete fermentation of carbohydrates assimilated by yeast confirmed the complementarity of the two raw materials used to prepare fermentation media, emphasizing the high potential of the proposed technological solution for ethanol fuel production. Full article

Lignocellulosic bioethanol is a promising renewable energy source that can reduce greenhouse gas emissions and improve energy security. However, its commercialization faces significant economic and environmental challenges, including high feedstock costs, complex pretreatment processes, expensive enzyme formulations, and substantial energy and water requirements. This review examines the key factors affecting its viability, including feedstock costs, enzyme efficiency, co-product generation, greenhouse gas emissions, water use, energy efficiency, and land use impacts. Recent advancements in pretreatment technologies, enzyme recycling, genetically engineered microbial strains, and fermentation strategies are discussed for their potential to improve process efficiency and reduce production costs. This review also explores co-product valorization, including lignin and biogas utilization, which can enhance the economic sustainability of bioethanol production by generating additional revenue streams, offsetting operational costs, and improving overall process efficiency. Identifying research gaps, it highlights the need for cost-effective feedstock supply chains, advanced enzyme technologies, and optimized fermentation methods. Additionally, the role of life cycle assessments and government policies, including subsidies, is considered in shaping production costs and the environmental impact. By integrating economic and environmental perspectives, this review provides insights into advancing the sustainable production of lignocellulosic bioethanol, emphasizing the importance of continued innovation to overcome existing challenges. Full article

The increasing demand for renewable energy sources has led to significant interest in second-generation biofuels derived from lignocellulosic biomass and waste materials. This review underscores the pivotal role of lignocellulosic biomass valorization in meeting global energy needs, mitigating greenhouse gas emissions, and fostering a circular bioeconomy. Key pretreatment methods—including steam explosion, pressure treatment, and chemical pretreatment—are analyzed for their ability to enhance the accessibility of cellulose and hemicellulose in enzymatic saccharification. Advances in cellulolytic enzyme development and fermentation strategies, such as the use of genetically engineered microorganisms capable of fermenting both hexoses and pentoses, are discussed in detail. Furthermore, the potential of biorefinery systems is explored, highlighting their capacity to integrate biomass valorization into biofuel production alongside high-value bioproducts. Case studies and recent trends in bioethanol and biogas production are examined, providing insights into the current state of research and its industrial applications. While lignocellulosic biofuels hold considerable promise for sustainable development and emissions reduction, challenges related to cost optimization, process scalability, and technological barriers must be addressed to enable large-scale implementation. This review serves as a comprehensive foundation for bridging the gap between laboratory research and industrial application, emphasizing the need for continued innovation and interdisciplinary collaboration in biofuel technologies. Full article

Specialty Saccharomyces cerevisiae strains have emerged as key contributors to innovations across various industries, offering unique functionalities that extend beyond conventional applications. This review explores the diverse roles of specialty S. cerevisiae in nutrition, winemaking, and bioethanol production. In the field of nutrition, yeast biomass serves as a sustainable and nutrient-dense source of proteins, vitamins, and bioactive compounds, presenting potential as a functional food ingredient. S. cerevisiae can bioaccumulate trace elements like selenium, zinc, and chromium, offering health benefits, but challenges in toxicity and biomass recovery must be addressed for safe use in supplements. In winemaking, S. cerevisiae enhances flavor profiles, improves fermentation efficiency, and reduces undesirable compounds, contributing to premium wine quality. The potential of S. cerevisiae in novel applications is vast, including the development of low-alcohol wines, cryotolerant strains for improved fermentation at lower temperatures, and reduced chemical additives, highlighting its versatility in enhancing wine quality and sustainability. Furthermore, specialty S. cerevisiae plays a pivotal role in bioethanol production, with strain selection and further improvement leading to enhanced yield and efficiency, particularly from lignocellulosic biomass. By examining the latest innovations in each of these areas, this review highlights the versatility and potential of specialty S. cerevisiae in advancing sustainable development and enhancing product quality across sectors. Full article