Bioethanol Production Research Articles

Yeast as a cell factory for fermentative production of ethanol from xylose

BackgroundXylose is the most plentiful pentose sugar found in the lignocellulosic biomass in hemicellulose fractions. This pentose sugar has high potential to use as raw material for bioethanol production, as hemicellulose fractions account for 20–30 % in the lignocellulose biomass. However, bioconversion of xylose into ethanol is challenging for industrial prospective a sonly few microbes encompass the pentose fermentation pathway. MethodsBioconversion of xylose into bioethanol using yeasts is preferred since these organisms are more resistant and have higher ethanol tolerance limit compared to bacteria. During fermentation process xylose is not readily consumed by the microbes like glucose. Metabolic engineering has so far been unsuccessful to furnish adequate outcomes; and one of the reasons of this is the lack of consideration of a range of environmental factors which play potential role fermentative ethanol production form xylose. Significant FindingsThis review focuses on the bioethanol production from xylose highlighting the metabolic engineering segment, when microbes enter into fermenting phase. On this basis, the best possible technology can be evolved for subsequent commercialization of the product.

An alternative process for bioethanol production from marine and freshwater algae using yeast for hydrolysis

This research develops a new process for production of bioethanol from marine and freshwater algae based on hydrolysis using yeast rather than the established methods of enzyme and acid hydrolysis. Yeast were isolated and adapted specifically for this process and the effectiveness of this hydrolysis was evaluated. This method was then evaluated within a full ethanol production process involving ozone pretreatment, and both hydrolysis and fermentation using yeast, under different nutrient supplementation regimes. The process effectiveness was evaluated for species of freshwater (Spirogyra hyalina) and marine (Kappaphycus alvarezii) algae. The yeast-based hydrolysis method outperformed acid and enzyme hydrolysis for both species of freshwater and marine algae, with particularly significant results for the freshwater algae. In the whole of process treatment, the yeast-based hydrolysis approach was effective when combined with ozone pretreatment for marine algae, and without any pretreatment for freshwater algae. The highest ethanol yield was achieved through fermentation with a yeast extract supplement present. These results indicate that ozone pretreatment, hydrolysis using yeast, and fermentation with the use of yeast extract as a nutrient are promising methods for economic ethanol production from seawater algae, and for freshwater algae where ozone pretreatment is not required.

Exploring sago potential in Meranti Islands Regency: A comprehensive analysis for sustainable bioethanol production in Indonesia

Exploring sago potential in Meranti Islands Regency: A comprehensive analysis for sustainable bioethanol production in Indonesia

Biogas Generation from Cotton Waste

Abstract: The anaerobic treatability and methane generation potential of three altered cotton wastes namely, cotton stalks, cotton seed hull and cotton oil cake remained determined in batch reactors. In addition, the effects of nutrient and trace metal supplementation were similarly investigated. The conversion of organics of cotton stem into bioenergy could serve the dual part of renewable energy production and waste reduction. Composition analysis demonstrated that cotton stem is a suitable feedstock for both bioethanol and biogas production. Anaerobic digestion of cotton stem attained 40.35% total biogas with 12.76% increased net CH4 volume compared to co-digestion of cotton stem with buffalo dung. Chopped cotton waste was considered as prospected substrate for biogas production. Cotton stalk was used gradually to exchange gobar content as substrate. During the study of four months the digester performed well till 90% feeding of cotton waste substrate. The maximum biogas generation detected was 1.3 m3 ; this shows that chopped cotton wastehas the potential to generate biogas. However, the digester was choked repeatedly and the concern of repetitive chocking of digester needs to be addressed.

Gaining insights into the responses of individual yeast cells to ethanol fermentation using Raman tweezers and chemometrics

Saccharomyces cerevisiae is the most common microbe used for the industrial production of bioethanol, and it encounters various stresses that inhibit cell growth and metabolism during fermentation. However, little is currently known about the physiological changes that occur in individual yeast cells during ethanol fermentation. Therefore, in this work, Raman spectroscopy and chemometric techniques were employed to monitor the metabolic changes of individual yeast cells at distinct stages during high gravity ethanol fermentation. Raman tweezers was used to acquire the Raman spectra of individual yeast cells. Multivariate curve resolution-alternating least squares (MCR-ALS) and principal component analysis were employed to analyze the Raman spectra dataset. MCR-ALS extracted the spectra of proteins, phospholipids, and triacylglycerols and their relative contents in individual cells. Changes in intracellular biomolecules showed that yeast cells undergo three distinct physiological stages during fermentation. In addition, heterogeneity among yeast cells significantly increased in the late fermentation period, and different yeast cells may respond to ethanol stress via different mechanisms. Our findings suggest that the combination of Raman tweezers and chemometrics approaches allows for characterizing the dynamics of molecular components within individual cells. This approach can serve as a valuable tool in investigating the resistance mechanism and metabolic heterogeneity of yeast cells during ethanol fermentation.

Utilization of food waste for bioethanol production in a circular bioeconomy approach

Utilization of food waste for bioethanol production in a circular bioeconomy approach

Valorization of Afzelia bella oilseeds cake in bioethanol production using 1-butyl-3-methyl-imidazolium chloride ionic liquid and dilute sulfuric acid pretreatment

The use of renewable feedstocks and the variability of lignocellulosic feedstocks generating fermentable sugars also offer the advantages of the most abundant, sustainable and competitive non-food biomass. The aim of this study is to valorize the oilcake obtained from non-conventional Congolese Afzelia bella oilseeds, after extraction of the oil used in biodiesel production. The conversion of A. bella oilseeds cake into ethanol was carried out using the two methods of pretreatment (with the synthesized ionic liquid 1-butyl-3-methyl imidazolium chloride and dilute sulfuric acid), followed by hydrolysis with dilute sulfuric acid and fermentation by Saccharomyces cerevisiae. The lignocellulosic composition of the sample was 47.98% cellulose, 28.15% hemicellulose and 22.3% lignin. Pretreatment with 1-butyl-3-methyl-imidazolium chloride (ionic liquid) showed an increase in cellulose content of around 4.25% and hemicellulose content of around 7.7%, with simultaneous delignification of 12.25%. In contrast, with dilute sulfuric acid, the lignin and cellulose content of the sample fell to 3.88% and 1.88% respectively. Hemicellulose content, on the other hand, increased by only 3.58%. After dilute acid hydrolysis (5% H2SO4), the values for total reducing sugar, glucose and xylose were 66.06±1.34 mg.g-1; 36.25 ± 1.2 mg.g-1 and 29.71 ± 0.6 mg.g-1 respectively. The percentage conversion of sugars was 55.16 ± 0.5% for cellulose to glucose and 53.76 ± 0.75% for hemicellulose to xylose. The hydrolyzed product of the complex polysaccharide was then converted to ethanol using commercial yeast. Results showed an ethanol yield of around 10.3%, and Fourier Transform Infrared (FTIR) spectroscopy results confirmed bioethanol production. A. bella oilseeds cakes are therefore a potential source for ethanol production.

Optimizing Bioethanol (C2H5OH) Yield of Sweet Sorghum Varieties in a Semi-Arid Environment: The Impact of Deheading and Deficit Irrigation

Bioethanol production offers promise in mitigating environmental impacts from ethanol consumption despite water scarcity. This study endeavors to evaluate the nuanced influence of different deheading times (45 days before harvest, 21 days before harvest, and no deheading) along with varying water regimes on select sweet sorghum cultivars (Honey, Willy, MN1500, and Atlas), focusing on yield traits, theoretical ethanol production, and water productivity. Findings underscore the substantial impact of cultivation practices on bioethanol yield. A water deficit ranging from 30% to 70% resulted in a discernible reduction in stalk yields of 17.86% to 18.54% and in sugar yields of 0.2 to 0.31 Mg ha−1, accompanied by a corresponding decline in theoretical ethanol yield of 120.9 to 180.9 L ha−1. Additionally, notable enhancements in Brix and sugar content of 16.32% to 18.42% and 16.81% to 19.03%, respectively, were observed across both seasons. Of particular significance, the Honey variety, subjected to a 30% water deficit and deheading at 21 days before harvest, demonstrated exceptional growth and yield characteristics. These empirical insights furnish valuable guidance for optimizing sweet sorghum cultivation practices, thereby augmenting sustainable bioethanol production and propelling forward the frontier of renewable energy technologies towards a more environmentally sustainable future.

Comparative assessment of pre-treatment techniques and process economics on marine seaweed, Gelidium pusillum, for enhanced bioethanol production

Many researchers are actively investigating different pre-treatment methods on alternative energy sources for sustainable production of bioethanol. With abundant carbohydrates and ease of cultivation, Gelidium pusillum, seaweed biomass has gained attention as a bioethanol feedstock. In the present study, various combinatorial pre-treatment methods like ultrasonic-acid treatment, microwave-alkali treatment, and steam-organic solvent treatment were carried out on seaweed biomass and compared for their efficiency in bioethanol production. Physico-chemical changes of biomass were characterized using Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy, and X-ray Diffraction. Among all pre-treatment methods, microwave-alkali treatment was found to be the most effective one and yielding fermentable sugars, sugar utilization efficiency, and ethanol concentration of 395 mg/g, 78.33 ± 0.98%, and 5.7 ± 0.19 g/L, respectively. Additionally, the process-economic analysis showed that Gelidium pusillum and microwave-alkali treatment could be scaled up to the industrial level with a production cost of $1.40 per liter of ethanol with minimal ecological impact.

Density and Composition of Cohabiting Bacteria in Chlorella vulgaris CCAP 211/21A Is Influenced by Changes in Nutrient Supply

Microalgae have considerable potential as a renewable feedstock for biochemical and bioethanol production that can be employed in processes associated with carbon capture. Large-scale microalgae cultivations are often non-axenic and are often cohabited by bacteria. A better understanding of the influence of cohabiting bacteria on microalgae productivity is required to develop sustainable synthetic co-culture processes at scale. Nutrient limitation is a frequently employed strategy in algal cultivations to accumulate energy reserves, such as lipids and carbohydrates. Here, a non-axenic culture of an estuarine green microalga, Chlorella vulgaris CCAP 211/21A, was studied under nutrient replete and deplete conditions to assess how changes in nutrient supply influenced the cohabiting bacterial population and its association with intracellular carbohydrate accumulations in the alga. Nutrient limitation resulted in a maximum carbohydrate yield of 47%, which was 74% higher than that in nutrient replete conditions. However, the latter condition elicited a 2-fold higher carbohydrate productivity. Three cohabiting bacterial isolates were cultivable from the three culture conditions tested. These isolates were identified using the 16S rRNA gene sequence to belong to Halomonas sp. and Muricauda sp. The composition of the bacterial population varied significantly between the growth conditions and time points. In all cases and at all time points, the dominant species was Halomonas isolates. Nutrient depletion resulted in an apparent loss of Muricauda sp. This finding demonstrates that nutrient supply can be used to control cohabiting bacterial populations in algal cultures, which will enable the development of synthetic co-culture strategies for improving algae productivity.

Assessment of deep eutectic solvents (DES) to fractionate Paulownia wood within a biorefinery scheme: Cellulosic bioethanol production and lignin isolation

Five deep eutectic solvents (DES) were evaluated to disrupt Paulownia wood structure to produce bioethanol and lignin. The DES formulated with choline chloride:lactic acid provided the most promising result. Temperature (110–130 °C), residence time (30–120 min), molar ratio (1:2–1:9), and liquid-to-solid ratio (8–15 mL/g) were optimized for cellulose recuperation (93% retained in the solid phase) and lignin removal (94% delignification yield). The spent solid was used for bioethanol production, achieving up to 43.6 g ethanol/L (89.7% ethanol yield). Lignin (84% of purity) was isolated from the black liquor and thoroughly characterized by FTIR, 1H NMR, TGA-DTG and SEM, while the liquor after lignin precipitation was chemically characterized for monomers/oligomers, total phenolic content, antioxidant activity and phytochemical profile (highlighting the presence of 25.06, 10.21 and 2.51 mg of syringaldehyde, vanillin and 3,4-dihydroxibenzoic acid per g of initial biomass). Overall, this study show that DES pre-treatment is a promising strategy for simultaneous lignin extraction and cellulose digestibility enhancement.

Catenovulum adriaticum sp. nov., isolated from algae in the harbour of Susak, Croatia.

The use of algae as feedstock for industrial purposes, such as in bioethanol production, is desirable. During a search for new agarolytic marine bacteria, a novel Gram-stain-negative, strictly aerobic, and agarolytic bacterium, designated as TS8T, was isolated from algae in the harbour of the island of Susak, Croatia. The cells were rod-shaped and motile. The G+C content of the sequenced genome was 38.6 mol%. Growth was observed at 11-37 °C, with 0.5-13 % (w/v) NaCl, and at pH 6.0-9.0. The main fatty acids were summed feature 3 (C16 : 1 ω6c and/or C16 : 1 ω7c), summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c), and C16 : 0. The main respiratory quinone was ubiquinone-8. The major polar lipids were phosphatidylethanolamine and phosphatidylglycerol. Analysis of 16S rRNA gene sequences indicated that the newly isolated strain belongs to the genus Catenovulum. Based on 16S rRNA gene sequence data, strain TS8T is closely related to Catenovulum sediminis D2T (95.7 %), Catenovulum agarivorans YM01T (95.0 %), and Catenovulum maritimum Q1T (93.2 %). Digital DNA-DNA hybridization values between TS8T and the other Catenovulum strains were below 25 %. Based on genotypic, phenotypic, and phylogenetic data, strain TS8T represents a new species of the genus Catenovulum, for which the name Catenovulum adriaticum sp. nov. is proposed. The type strain is TS8T (=DSM 114830T=NCIMB 15451T).

Comparative Review on the Production and Purification of Bioethanol from Biomass: A Focus on Corn

In the contemporary era, conventional energy sources like oil, coal, and natural gas overwhelmingly contribute 89.6% to global CO2 emissions, intensifying environmental challenges. Recognizing the urgency of addressing climate concerns, a pivotal shift towards renewable energy, encompassing solar, wind, and biofuels, is crucial for bolstering environmental sustainability. Bioethanol, a globally predominant biofuel, offers a versatile solution, replacing gasoline or integrating into gasoline–ethanol blends while serving as a fundamental building block for various valuable compounds. This review investigates the dynamic landscape of biomass generations, drawing insightful comparisons between the first, second, third, and fourth generations. Amid the drive for sustainability, the deliberate focus on the initial generation of biomass, particularly corn, in bioethanol production is grounded in the current dependence on edible crops. The established utilization of first-generation biomass, exemplified by corn, underscores the necessity for a comprehensive examination of its advantages and challenges, allowing for a nuanced exploration of existing infrastructure and practices. To produce bioethanol from corn feedstock, various milling methods can be employed. Thus, this paper delves into a comparative assessment of dry-milling and wet-milling processes scrutinizing their efficiency, environmental impact, and economic feasibility.

Fungal population and physicochemical properties of bioethanol produced from cassava (<i>Manihot esculenta</i>)

The quest for affordable and environmentally friendly fuel has led to the production of bioethanol from agricultural products. This study was undertaken to produce alcohol from cassava by the fermentative action of Aspergillus niger and Saccharomyces cerevisiae. The fermentation process comprised of two (2) set ups- one was fermented by Aspergillus niger and the other was fermented by Saccharomyces cerevisiae. The fermentation process lasted for 12 days and it was distilled on the 14th day. The process was monitored and controlled by carrying out physicochemical (pH, temperature, specific gravity, alcohol content) and microbiological analyses using standard methods. There was a decrease in the pH for both set ups during the course of the fermentation. The temperature was between 25.0oC to 30.5oC for both setups. The specific gravity decreased during the course of the fermentation from 1.03 to 0.01 which led to an increase in the alcohol content from 0 to 55% for the setup that involved Aspergillus niger and 1.02 to 0.03 which led to an increase in the alcohol content from 0 to 50% for the setup that involved Saccharomyces cerevisiae. There was an increase in the total fungal count from 4.4 ×102 to 5.9×102 CFU/ml from day1 to 7 and a decrease from 5.9 ×102 to 0 CFU/ml from days 7 to after distillation for the setup that involved Aspergillus niger. There was also an increase in the total yeast count from 1.6 ×102 to 2.9 ×102 from days 1 to 7 and a decrease from 2.9 ×102 to 0 from days 7 to after distillation for Saccharomyces cerevisiae. This study shows that alcohol can be successfully produced from cassava using Aspergillus niger and Saccharomyces cerevisiae.

Efficient enzymatic saccharification of agricultural wastes for the production of bioethanol, D-allulose and lactic acid

The demand for renewable resources to replace fossil fuels has increased. Fruit and agricultural wastes can be fermented to yield biofuels and biochemicals. However, the high cost of the feedstock and limitations of the catalytic process hinder the application of such wastes. Therefore, we aimed to develop an efficient enzymatic saccharification process, without pretreatment, for fruit and agricultural wastes. The conversion rate of the mixed agricultural wastes (MAW) to fermentable sugars was approximately 91 % after 24 h. The ethanol yield increased by 4.5 % after limonene removal. The D-allulose yield in the hydrolysate was 4.6 mg/mL at 4 °C and 3.3 mg/mL at 50 °C, whereas the fructose yield in the sugar medium was 13.2 mg/mL at 4°C, demonstrating a high conversion yield of 73.2 %. Lactic acid was produced at a conversion rate of approximately 67.4 %. Therefore, this study presents a novel approach of the biosynthesis of functional sugars and chemicals from waste biomass, introducing a cost-effective enzymatic saccharification process that bypasses pretreatment, thereby enabling the production of biofuels, biochemicals, and functional sugars and opening up a promising economic opportunity in the field.

Theory to practice: a success in breeding sugarcane variety YZ08-1609 known as the King of Sugar.

Sugarcane, a significant cash crop in tropical and subtropical regions, contributes to 80% of sugar production and 40% of bioethanol production in the world. It is a key sugar crop, accounting for 85% of sugar production in China. Developing new varieties with high yield, high sugar, and better stress resistance is crucial for the sustainable growth of sugar industry. Hybrid breeding is the most widely used and effective method, with over 98% of Chinese sugarcane varieties resulting from this approach. Over the past two decades, Chinese breeders have developed the theory of high-heterogeneous composite high-sugar breeding, leading to the successful breeding of the fifth-generation sugarcane varieties. Among them, YZ08-1609, a complex hybrid of Saccharum spp., was developed by Sugarcane Research Institute (YSRI) of Yunnan Academy of Agricultural Sciences. The average cane yield of YZ08-1609 was 14.4% higher than ROC22. It is highly resistant to mosaic disease, and highly tolerant to drought stress, but moderately susceptible to smut disease. Notably, YZ08-1609 stands out with a sucrose content of 20.3%, setting an international record, earning the reputation as "King of Sugar". To summarize experience and inspire breeding, we provided here the detailed insights into the selection of parents, breeding process, and characteristics of YZ08-1609. Besides, the biological mechanisms underlying its high yield and high sugar was excavated at both transcriptional and metabolic levels. The challenges and prospects in breeding sugarcane varieties especially with high sugar were also discussed, offering a foundation for the future development of high-sugar varieties.

Sustainability Assessment of 2G Bioethanol Production from Residual Lignocellulosic Biomass

The development of sustainable biofuels can help to reduce the reliance on fossil fuels and mitigate the impact of climate change. This study analyzes bioethanol production from agro-forestry residual biomass, namely eucalyptus residues and corn stover. The study includes process simulation using Aspen Plus software, followed by economic analysis and life cycle assessment (LCA) with the help of SimaPro software and by applying the environmental footprint (EF) 3.0 method. The economic analysis on the biorefinery’s economic viability, equipment, and production costs reveals a positive decision for bioethanol production from eucalyptus residues due to logistical and transportation costs. The minimum ethanol selling price (MESP) obtained was 2.19 €/L and 2.45 €/L for eucalyptus residues and corn stover, respectively. From the LCA with a functional unit of 1 MJ of ethanol, bioethanol production from eucalyptus residues results in a single score impact of 37.86 µPt, whereas for corn stover, it is 33.47 µPt. In the climate change impact category, the eucalyptus residues scenario has an impact of 0.264 kg CO2 eq/MJ ethanol while corn stover leads to 0.254 kg CO2 eq/MJ ethanol. In-situ enzyme production, heat integration, and the use of renewable energy sources were also analyzed. Combining in situ enzyme production with renewable energy sources lowers CO2 equivalent emissions by 89% for both feedstocks, in comparison to the base-case scenario.

Bioethanol from Arthrospira platensis biomass using a combined pretreatment

With the aim to reduce the reliance on gasoline by supporting efficient bioethanol production to meet the biofuel goal of 46 % in the transportation sector by 2050, the present study proposes a combined pretreatment of microwave-assisted acid hydrolysis for bioethanol production, which was applied to commercially-produced microalgal biomass of Arthrospira platensis. The Separated Hydrolysis and Fermentation (SHF) method was applied to prevent sugar loss and produce a higher bioethanol yield. After examining the effect of acid concentrations (0, 0.1, 0.2, and 0.3 M) and hydrolysis duration (30, 60, 90, 120, and 180 min) on the fermentable sugars, it was discovered that both operation parameters had a major impact on the synthesis of monosaccharides. With a 0.3 M H2SO4 concentration and a 90-minute hydrolysis time at 100 °C, the maximum concentration of fermentable sugars of 11.60 g/L was obtained. Regarding the fermentable sugar yield, the suggested combined pretreatment (78.4 %) outperforms the literature-reported single pretreatment of acid hydrolysis (55 %), under comparable operating settings. After 96 h of anaerobic fermentation with Saccharomyces cerevisiae, the hydrolysate of the fermentable sugars produced 0.06 g ethanol/g biomass, corresponding to 0.35 g ethanol/g total carbohydrates in Arthrospira platensis.

Pretreatment of lignocellulosic biomass for bioethanol production

This review surveys recent progress in pretreatment methods for enhancing bioethanol production from lignocellulosic biomass. Various pretreatment techniques, including physical, chemical, and biological approaches, are evaluated for their efficacy in breaking down biomass structure and improving enzymatic digestibility. Key parameters influencing pretreatment effectiveness and integration with downstream processes are discussed. The review highlights promising strategies and identifies areas for further research to optimize bioethanol production from lignocellulosic feedstocks.

Grades of cassava starch (flours) as sustainable substrates for use in neutral spirit and biofuel production—Industry approach

One way to mitigate the adverse impacts of climate change is through aggressive replacement of fossil energy sources with plant derived renewable energy. The potential of different grades of cassava starch, including decayed cassava starch, as viable alternative and cheaper source of renewable raw materials for bio-ethanol production was studied. The global population keeps expanding and poverty levels keep increasing. Conflict in the use of food-grade cassava starch as raw material for bio-ethanol production will pose a threat to food security. The highest alcohol yield (AY) of 539 LA/t dm was obtained from food grade cassava starch. Food grade cassava starch per-boiled for 5 min produced lower AY (524 LA/t dm). Cassava starch per-boiled for more than 5 min gave much lower AY (507 LA/t). The mildly decayed cassava starch gave a relatively higher AY of 491 LA/t dm than the more decayed cassava substrate that produced AY of 453 LA/t dm. The AY value obtained from the more decayed cassava starch is similar to the AY values obtained with some cereals. Decayed cassava is not fit for human consumption, would not compete with food requirements. This will assist in food security, secure our environment from pollution and other adverse effects.