Search Results (177)

The economic viability of second-generation (2G) bioethanol production depends on the availability of robust, multistress-tolerant yeast strains capable of withstanding harsh industrial conditions. This study investigates animal manure as a novel ecological niche for discovering such strains, as microbes in these environments naturally adapt to high organic loading and fluctuating temperatures. From eighty-six initial isolates, twenty-nine demonstrated superior xylose fermentation at 37 °C. Eight high-performing isolates (C2-1, B1-2, B1-6, B2-6, B2-8, G1-4, G1-5, and G2-4) exhibited exceptional tolerance to ethanol, high temperatures, and lignocellulosic-derived inhibitors (acetic acid, formic acid, furfural, and vanillic acid). Molecular identification classified isolate C2-1 as Pichia kudriavzevii and the remaining seven as Candida tropicalis. In synthetic media, C. tropicalis B2-8 produced up to 16.33 g/L of ethanol using xylose (60 g/L) as the sole carbon source. While the undetoxified, highly acidic sugarcane bagasse hydrolysate completely inhibited yeast growth, the industrial potential of these strains was successfully validated using the concentrated, undetoxified enzymatic hydrolysate derived from the acid-pretreated sugarcane bagasse solids, which contained 30.15 g/L glucose and 25.58 g/L xylose. P. kudriavzevii C2-1 achieved ethanol titers of 6.02 g/L and 5.71 g/L at 37 °C and 40 °C, respectively. The C. tropicalis strains outperformed P. kudriavzevii, yielding 6.12–6.35 g/L at 37 °C and maintaining 5.75–6.19 g/L at 40 °C. These findings underscore the potential of manure-derived yeasts as resilient biocatalysts. Although their fermentation yields remain relatively low and require further metabolic optimization, their ability to survive and ferment in this concentrated, undetoxified enzymatic hydrolysate at elevated temperatures makes them promising candidates for further development in high-temperature ethanol fermentation (HTEF), offering a potential pathway toward reducing cooling costs associated with 2G biorefineries. Full article

The mitigation of anthropogenic climate change caused by fossil fuel combustion is a critical global challenge that necessitates a transition to renewable energy systems. Bioethanol represents a major renewable fuel, but first-generation production relies on edible feedstocks, which raises concerns regarding food security. Consequently, research is shifting toward second-generation bioethanol produced from abundant non-edible lignocellulosic biomass sources. This review comprehensively examines the potential of Candida krusei (synonyms: Pichia kudriavzevii, Issatchenkia orientalis) to serve as an alternative biocatalyst for second-generation bioethanol production. Compared with the first-generation bioethanol-producing yeast Saccharomyces cerevisiae, C. krusei exhibits superior physiological traits, such as thermo, acid, and inhibitor tolerances, enabling the utilization of several lignocellulosic feedstocks. This review summarizes the taxonomic and physiological characteristics of C. krusei, describes case studies on bioethanol production, and discusses strategies for reducing production costs. Furthermore, the technical and biosafety challenges associated with the industrial deployment of C. krusei are critically examined, including xylose metabolism limitations, scale-up constraints, and the management of its opportunistic pathogenic nature. A life cycle assessment perspective suggests that the unique physiological properties of C. krusei contribute to reducing greenhouse gas emissions and energy consumption throughout the entire production process, from pretreatment to downstream ethanol recovery. 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

In laboratory installations, wastewater from the distillery industry (ethanol stillage and vinasse) is treated via a two-stage combination of microbial sulfate reduction (MSR) and biomethanation, assisted by bioelectrochemical systems (BESs). In the first stage, a sulfidogenic bioreactor with an integrated microbial fuel cell (MFC) is used, which partially oxidizes the produced H₂S and facilitates the conversion of organic compounds. Sulfate removal reaches 95.4% (stillage) and 92.8% (vinasse), with corresponding COD reductions of 30.6% and 36.5%, respectively. The polarization curves, power density, generated current, and coulombic efficiency are analyzed. The sulfidogenic bioreactor consortium is dominated by Deltaproteobacteria, which contributes to acetate accumulation during the MSR stage. Methanogens are dominated by the genus Methanofolis. In the second stage of anaerobic digestion, three treatment options are investigated: direct biomethanation, biomethanation after preliminary MSR, and biomethanation after MSR with a microbial electrolysis cell (AD-MEC). The highest COD conversion rates are achieved in the AD-MEC variants: 91.36% for ethanol stillage and 92.8% for vinasse. Microbial communities are dominated by acetoclastic methanogens of the genus Methanothrix. For stillage treated after MSR, biogas production is nearly double that from direct methanation. For vinasse, the largest amount of biogas is generated during by the integrated MEC system, followed direct methanation. Methane content is the highest in methanation after MSR in AD-MEC (93.4–93.6%). Full article

The reactive double dividing-wall distillation column (R-DDWDC) can simultaneously integrate and effectively coordinate reaction–separation coupling (RSC) and separation–separation coupling (SSC), thereby offering greater technical advantages and development potential than the conventional reactive distillation column and the reactive single dividing-wall distillation column. However, the application of two dividing walls and the introduction of external recycle flows inevitably lead to multiple candidate configurations of the R-DDWDC, and this significantly adds complexity and computational burden to its synthesis and design. To address the issue, we propose an effective methodology for developing the R-DDWDC, which involves a two-step strategy: the first step is to determine the configuration of external recycle flows by searching for the RSC from non-sharp separation to sharp separation of reaction mixtures, and the second step is to adjust the arrangement of the dividing walls to intensify the SSC. The former serves to provide the greatest flexibility for the inclusion of the SSC, and the latter helps to achieve full coordination with the RSC, thereby allowing the determination of the optimal design with low complexity and computational intensity. The methodology is fundamentally a conceptual design and structural optimization framework that can be implemented using either generic process simulation platforms or custom computational programs. Four representative examples, including the metathesis of 2-pentene; the acetalization of ethanol with butanal; the transesterification of propylene glycol monomethyl ether with methyl acetate; and the esterification of lactic acid with methanol, are selected to assess the derived procedure, and the obtained results confirm its simplicity and efficiency. Because the procedure proposed in this work is independent of the number of components contained in reaction mixtures and their relative volatility rankings, it can be regarded as a general methodology for developing other complicated reactive dividing-wall distillation columns. Full article

Driven by the energy transition within the framework of the United Nations Framework Convention on Climate Change, second-generation (2G) ethanol stands out as a technical and sustainable alternative to fossil fuels. Although first-generation ethanol, produced from saccharine and starchy feedstocks, represents an advance in mitigating emissions, its expansion is limited by competition with areas destined for food production. In this context, 2G ethanol, obtained from residual lignocellulosic biomass, emerges as a strategic route for diversifying and expanding the renewable energy matrix. Thus, this work discusses the current state of 2G ethanol technology based on the gradual growth in production and the consolidation of this route over the last few years. Industrial second-generation ethanol plants operating around the world demonstrate the high potential of agricultural waste as a raw material, particularly corn straw in the United States, which offers a lower cost and significant yield in the production of this biofuel. Similarly, in Brazil, sugarcane by-products, especially bagasse and straw, are consolidating as the main sources for 2G ethanol, integrated into the biorefinery concept and the valorization of by-products obtained during the 2G ethanol production process. However, despite the wide availability of lignocellulosic biomass and its high productive potential, the consolidation of 2G ethanol is still conditioned by technical and economic challenges, especially the high costs associated with pretreatment stages and enzymatic cocktails, as well as the formation of inhibitory compounds that compromise the efficiency of the process. Genetic engineering plays a particularly important role in the development of microorganisms to produce more efficient enzymatic cocktails and to ferment hexoses and pentoses (C₆ and C₅ sugars) into ethanol. In this scenario, not only are technological limitations important but also public policies and tax incentives, combined with the integration of the biorefinery concept and the valorization of (by)products, which prove fundamental to reducing costs, increasing process efficiency, and ensuring the economic viability and sustainability of second-generation ethanol. Full article

Chronic ethanol exposure and genetic factors interact to drive neuroadaptations in alcohol use disorders (AUD). However, the system-level coordination of molecular responses across brain regions remains unclear. The 5-HT system and BDNF are key regulators of neuroplasticity in alcoholism. The 5-HT₇ receptor modulates both behavior and serotonin signaling. We investigated midbrain 5-HT₇ overexpression in C57BL/6 mice given 5-week ethanol access. Our results showed complex, region-specific changes in 5-HT and BDNF signaling, as well as selective behavioral alterations. Ethanol abolished the antidepressant-like effect of 5-HT₇ overexpression and increased anxiety-like behavior, without affecting baseline locomotion or novel object recognition. At the molecular level, ethanol suppressed 5-HT₇-mediated CREB/BDNF signaling and differentially regulated 5-HT_1A and 5-HT_2A expression across regions. To extract general principles, we used integrative systems analysis based on population-averaged generalized estimating equations (GEE), and mapped effects in the (t₁, t₂) plane. We identified two regularities: first, regional specificity of responses, and second, divergence across regulatory levels, with opposing effects more frequent at the mRNA level and concordant effects more common at the protein level. These findings suggest that neuroadaptation to combined 5-HT₇ and ethanol factors follows region- and level-specific rules, rather than a single global program, underscoring the value of integrative analysis. Full article

The objective of this study was to valorise eggshell waste (ESW) by investigating its biosorption properties and evaluating its efficiency as a sustainable biosorbent for the removal of the synthetic dye Congo Red (CR) from model CR solutions and synthetic wastewater with the addition of CR. Batch biosorption experiments were conducted to investigate the influence of several factors on the biosorption process, including ESW concentration (1–15 g L⁻¹), contact time (1–360 min), temperature (15, 25, 35, 45 °C) and initial CR concentration (10–100 mg L⁻¹). Desorption experiments were performed using ultrapure water, 0.1 M NaCl, 50% ethanol, 0.1 M HCl, or 0.1 M NaOH as solvents. A higher ESW concentration improved CR removal, but the amount of CR adsorbed on ESW decreased. The dye uptake by ESW was increased with prolonged contact time and temperature increase. When the effect of CR initial concentration was investigated, the results indicated that the process is concentration-dependent and that overall, CR uptake by ESW was higher in synthetic wastewater than in the model dye solution. The biosorption process was better described by the Langmuir isotherm model than by the Freundlich model, indicating monolayer adsorption. Kinetic analysis showed that the pseudo-second-order model provided a better fit than the pseudo-first-order model. Desorption of CR from ESW under the applied experimental conditions was generally low (0.67–27.13%). Full article

The valorization of lignocellulosic biomass has been attracting interest in several industrial areas due to its potential to produce high-value-added compounds. Among these products, lignocellulosic enzymes stand out, capable of degrading biomass into fermentable polysaccharides, essential to produce second-generation ethanol and other bioproducts. The genus Pleurotus spp., a macrofungus with a high enzyme production capacity, has been consolidating itself as a promising alternative in the bioconversion of lignocellulosic residues. Contextually, this review explores for the first time the level of technology readiness associated with the production of enzymes by Pleurotus spp., in addition to addressing advances in patent filings and the role of these enzymes in the conversion of lignocellulosic biomass. Through a technological analysis based on a critical evaluation of 250 studies indexed in the database Scopus^® between 2015 and 2025, from which 16 studies were selected for a detailed and rigorous assessment of enzyme production by Pleurotus spp., it was observed that technological progress remains at the laboratory scale, in TRL 3 and 4, with few studies at the TRL 5 scale. In addition, the factors that may be affecting the increase in technological readiness of microbial enzyme production at pilot and industrial scales are discussed. The valorization of lignocellulosic biomass and the production of enzymes by macrofungi represent a promising path towards sustainability and cost reduction; however, significant challenges remain related to pilot-scale studies and increasing the level of technological maturity of these processes by Pleurotus spp., requiring further investigation of these processes to standardize and enable their industrial scale-up. Full article

Lignin is the most structurally complex component of lignocellulosic biomass. Each year, thousands of tons of lignin-rich residues from enzymatic hydrolysis are generated in sugarcane-based cellulosic ethanol biorefineries. The current study specifically utilizes lignin extracted from sugarcane bagasse as the primary feedstock for biochar production, rather than employing the raw bagasse itself. This study investigates, through pyrolytic thermal treatment of two lignin sources, the production of biochars and the evaluation of their potential applications. Kraft commercial lignin and sugarcane bagasse lignin samples, along with their corresponding biochars, were characterized by elemental and proximate analyses, higher heating value determination, spectroscopic techniques, thermogravimetric analysis, X-Ray diffraction, scanning electron microscopy coupled with energy-dispersive spectroscopy, and true density measurements. The results revealed a lower contamination level associated with the extraction process and confirmed the amorphous nature of sugarcane bagasse lignin and its derived biochar. An O/C ratio of approximately 0.3 was obtained for the sugarcane bagasse lignin biochar based on both elemental and Raman spectroscopy analyses. Both elemental composition assessment and Raman spectroscopic analysis indicated that all biochar specimens exhibited hydrogen-to-carbon (H/C) ratios exceeding 0.5. The analyses, therefore, indicated that the biochar derived from sugarcane lignin exhibited higher energy density, moderate stability and a high carbon content. The proposed approach thus provides promising alternatives for the valorizing lignin residues derived from second-generation ethanol production processes. Full article

Brewer’s spent grain (BSG), the main lignocellulosic by-product of the beer industry, represents an abundant yet underutilized resource with high potential for valorization. This study presents an integrated biorefinery approach to convert BSG into second-generation (2G) ethanol, bioactive vinasse for plant growth promotion, and fungal biomass as a potential mycoprotein source. The biomass was first subjected to biological delignification using the white-rot fungus Ganoderma lucidum, after which two valorization routes were explored: (i) evaluation of the fungal biomass as a mycoprotein candidate and (ii) alcoholic fermentation for ethanol production. For the latter, three pretreatment strategies were assessed (diluted sulfuric acid and two deep eutectic solvents (DESs) based on choline chloride combined with either glycerol or lactic acid) followed by a one-pot enzymatic saccharification and fermentation using Kluyveromyces marxianus SLP1. The highest ethanol yield on substrate (Y_P/S) was achieved with [Ch]Cl:lactic acid pretreatment (0.46 g/g, 89.32% of theoretical). Vinasse, recovered after distillation, was characterized for organic acid content and tested on Solanum lycopersicum seed germination, showing promising biostimulant activity. Overall, this work highlights the potential of BSG as a sustainable feedstock within circular economy models, enabling the production of multiple bio-based products from a single residue. Full article

The global sparkling wine market continues to grow steadily, reaching approximately 24 million hectoliters in 2023, with an annual increase of around 4% despite a general decline in overall alcoholic beverage consumption. This growth highlights the importance of employing diverse yeast strains to improve product variety and quality. Flor yeasts are specialized strains of Saccharomyces cerevisiae that develop a biofilm on the surface of certain wines during biological ageing. They possess unique physiological properties, including high ethanol tolerance and the capacity to adhere, which supports wine clarification. They also have the ability to contribute unique volatile compounds and aroma profiles, making them promising candidates for sparkling wine production. This study evaluated two flor yeast strains (G1 and N62), which were isolated from the Pérez Barquero winery during the second fermentation process using the traditional method. Sparkling wines were produced by inoculating base wine (BW) with each strain, and the wines were monitored at 3 bar CO₂ pressure and after 9 months of ageing on lees. Comprehensive metabolomic analysis was performed using GC-MS for volatile compounds and HPLC for nitrogen compounds, with statistical analysis including PCA, ANOVA, Fisher’s LSD, and correction FDR tests. Strain N62 demonstrated faster fermentation kinetics and higher cellular concentration, reaching 3 bar pressure in 27 days compared to 52 days for strain G1. Both strains achieved similar final pressures, 5.1–5.4 bars. Metabolomic profiling revealed significant differences in the profiles of volatile and nitrogen compounds between the two strains. G1 produced higher concentrations of 3-methyl-1-butanol, 2-methyl-1-butanol, and acetaldehyde, while N62 generated elevated levels of glycerol, ethyl esters, and amino acids, including glutamic acid, aspartic acid, and alanine. These findings demonstrate that both flor yeast strains successfully complete sparkling wine fermentation while producing distinct metabolic signatures that could contribute to unique sensory characteristics. This supports their potential as alternatives to conventional sparkling wine yeasts for enhanced product diversification. 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

Brazil is a leading producer of multi-purpose crops—such as corn, soybean, and sugarcane—used for human consumption, animal feed, and biofuel production. This study generated agricultural inventories for these three crops based on state-level information. For sugarcane, we used primary data submitted by ethanol producers to RenovaBio. For soybean and corn, we retrieved and updated data from a previous study, which gathered information through panel consultations with farmers and sector experts. We also calculated the greenhouse gas (GHG) emissions associated with the crops using the Life Cycle Assessment (LCA) method. Our analysis revealed significant variability in emissions across states, especially for corn and sugarcane. Without considering direct land use change (dLUC), the states with the highest and lowest emissions for each crop were as follows: (i) sugarcane: Paraíba at 54 and Goiás at 37, with a national average of 42 kg CO₂e/t cane; (ii) soybean: Maranhão at 344 and Minas Gerais at 300, average of 323 kg CO₂e/t soy; (iii) first-crop corn: Maranhão at 416 and Mato Grosso at 264, average of 300 kg CO₂e/t corn; (iv) second-crop corn: Paraná at 306 and Minas Gerais at 153, average of 255 kg CO₂e/t corn. Emissions were inversely related to crop yields, with the exception of second-crop corn. In general, lower yields were observed in states of the Northeast region (e.g., Maranhão and Paraíba), which face challenges due to irregular climate patterns and water deficits. For sugarcane cultivated in the same region, emissions from straw burning had a significant impact, with the practice being applied to more than 60% of the crop area. If dLUC emissions were included, variability would increase dramatically—particularly for corn and soybean in some states—due to patterns of cropland expansion into native vegetation areas over the 2000–2019 period. In particular, total soybean emissions would range from 471 in Paraná to 2173 in Maranhão, with a national average of 1022 kg CO₂e/t soy. These findings can be valuable as references for life cycle databases, for the development of state-specific emission factors for biofuels produced from the investigated crops, and as supporting information for decarbonization programs. Full article

Producing second-generation (2G) bioethylene through the dehydration of 2G bioethanol is a challenge, requiring the effective use of catalysts as an alternative to fossil-based ethylene production. This work evaluates the production of bioethylene from the catalytic dehydration of 2G bioethanol [from pine sawdust produced via a simultaneous saccharification and fermentation SSF process (53%)] using γ-Al2O3; ZSM-5, NH₄⁺Y, H-ZSM-5, and H-Y zeolite as catalysts. Yields of 94.6% (at 372 °C) and 85.5% (at 473 °C) of 2G bioethylene were obtained when using H-ZSM-5 and H-Y zeolite, respectively. These results demonstrate that the H-ZSM-5 zeolite showed the best performance for 2G bioethanol dehydration, producing high 2G bioethanol conversion and 2G bioethylene selectivity at a lower reaction temperature. Ethylene production from the catalytic dehydration of commercial (96%) and diluted (53%) ethanol was evaluated as a reference, along with the effects of the weight hourly space velocity (WHSV) and ethanol concentration. Varying the WHSV from 2.37 to 4.73 h⁻¹ at 312 °C and using commercial ethanol at 96%, produced similar ethanol conversion of 100% and ethylene yield of 100%. At 290 °C, with a WHSV of 2.37 h⁻¹ and 53% diluted commercial ethanol, H-ZSM-5 converted 76.83% of the ethanol and produced a 75.8% ethylene yield. A study based on density functional theory (DFT) has shown that diethyl ether is a key intermediate in the conversion mechanism on H-ZSM-5, proceeding through an ethoxide intermediate in the rate-determining step, with an apparent activation energy of 25.4 kcal mol⁻¹. Full article