Potential For Bioethanol Production Research Articles (Page 1)

Agro-processing residues are often undervalued and improperly disposed of in many developing countries, which contribute to environmental pollution and resource loss. This study evaluated the compositional characteristics and bioethanol production potential of underutilized postharvest residues from Basmati rice and sweet sorghum grown in Kenya. Proximate composition was determined using standard AOAC methods, while FT-IR and HPLC were used to characterize structural carbohydrates and fermentable sugars, respectively. The substrates were pretreated with dilute sulfuric acids (1.2 and 2.25%, w/w), detoxified with 2 M Ca(OH)2, pH 9, saccharified using cellulase enzymes, and fermented with Saccharomyces cerevisiae. Proximate analysis revealed moisture (4.3–9.1%) Protein (3.5–7.4%), fat (0.35–1.2%), ash (8.6–20.2%), and fiber (21.9–34.9%) contents. The substrates contained 32.1–39.7% cellulose, 26.0–29.4% hemicellulose, and 7.5–18.8% lignin. Glucose was the predominant fermentable sugar across all the substrates, with Basmati and Nerica husks containing the highest levels and yielding the greatest ethanol outputs of 8.9% and 8.43%, respectively, under 2.25% acid pretreatment. This study provides baseline data on postharvest residues from Basmati rice and sweet sorghum grown in Kenya and demonstrate their viability as promising feedstock for the production of second-generation bioethanol.

Microalgae are promising feedstocks, holding great potential for bioethanol production. However, microalgal bioethanol production requires the use of different approaches in order to optimize the process. In this study, the bioethanol production capacities of local yeasts (Saccharomyces cerevisiae, Candida boidinii and Kluyveromyces marxianus) from Chlorella vulgaris biomass cultivated with 0.5 g/L carrot pomace sugar was investigated. Onion peel, a common waste product, was used for investigating its potential in improving yeast growth and bioethanol production by K. marxianus. Parameters such as biomass loading (50-200 g/L), onion peel waste concentration (1%-5%), and supplement types (nitrogen sources and mineral salts such as peptone, yeast extract, MgSO4, KH2PO4, CaCl2, ZnSO4) were optimized. Among local yeasts, K. marxianus demonstrated the highest bioethanol production and productivity with a measured value of 4.29 ± 0.25 g/L and 0.36 g/L.h, respectively. Bioethanol concentration and productivity increased to 6.98 ± 0.12 g/L and 0.58 g/L.h, respectively, when 200 g/L biomass loading and 3% onion peel concentration was used. This study demonstrates the high potential of K. marxianus in metabolizing microalgal carbohydrates and the utilization potential of food waste as an inexpensive nutrient source in the fermentation medium.

Shortage of fossil fuels and rising greenhouse gas emissions have increased global interest in biofuel production and renewable energy. This study aimed to isolate, screen, and characterize ethanol-tolerant wild indigenous yeasts with high bioethanol yield from areke, a traditional fermented alcoholic product, collected at different production stages from diverse sites. Methods included isolation, screening based on pH, temperature, ethanol tolerance, carbohydrate assimilation, ethanol production measurement, and molecular identification. From 270 isolates, 10 (3.7%) tolerated 22% ethanol, and 4 (1.5%) tolerated 23% ethanol and were selected for further analysis. Ethanol production from sugarcane molasses was determined using the Hall method and verified with an Ebulliometer. Among these, two isolates (Mda and Dt1e) showed the highest bioethanol yields of 14.3% v/v and 13.2% v/v, respectively, at pH 4.39, 35 °C, and 30° Brix molasses concentration under shaking conditions. Morphological, colony, and molecular analyses identified the isolates as Saccharomyces cerevisiae and Kluyveromyces marxianus. This study demonstrates the presence of highly ethanol-tolerant, acid- and heat-resistant indigenous yeasts with excellent bioethanol production potential, supporting their recommendation for industrial bioethanol production.

Lignocellulosic materials, such as soybean hulls, possess a complex and recalcitrant structure that requires efficient pretreatment or enzymatic processing for effective conversion into valuable products. However, pretreatment processes often generate inhibitory byproducts (e.g., furfural, hydroxymethyl furfural (HMF), phenols, and lignin degradation products), which can impede enzymatic activity and increase overall production costs. This study explores soybean hulls, a byproduct of oil and meal production, as a potential high-carbohydrate biorefinery resource, assessing their chemical composition, fermentable sugar recovery, and bioethanol production potential. Soybean hulls (5%, w/v dry basis) were subjected to enzymatic hydrolysis at 50 °C for 72 hours, utilizing a dual impeller mixing system at 250 rpm. An enzyme load of 45 mg enzyme protein per gram of solids was applied using a combination of commercial enzyme preparations, including Cellulase Blend and Multifect Pectinase. Conversion of cellulose, xylan, and arabinan into fermentable sugars was quantified. A moderate enzyme loading of 10 mg enzyme protein/g solids was also tested for comparison. Microbial fermentation was carried out using the xylose-fermenting Escherichia coli FBR5 strain to produce bioethanol. Hydrolysis of untreated soybean hulls resulted in conversion yields of 94.4% for glucan, 72.6% for xylan, and 69.3% for arabinan into glucose, xylose, and arabinose, respectively. In comparison, control experiments without cellulolytic enzymes showed significantly lower conversion yields (14.2%, 20.1%, and 15.5% for glucose, xylose, and arabinose, respectively). A moderate enzyme loading of 10 mg enzyme protein per gram of solids achieved a cellulose conversion of 90.6%, which was nearly equivalent to the conversion obtained with 45 mg enzyme protein/g solids. Microbial fermentation with E. coli FBR5 resulted in 94% theoretical ethanol yield, with a production rate of 0.33 g/L/h and a productivity of 0.48 g ethanol/g sugar. The study demonstrates that enzymatic hydrolysis of soybean hulls, which are rich in cellulose and hemicellulose, can be effectively conducted without the need for pretreatment. The moderate enzyme load used in this study provides a promising platform for efficient sugar release and bioethanol production, presenting a cost-effective and viable approach for utilizing soybean hulls in biorefinery applications.

The cellulase RuCel224, derived from the rumen metagenome, was successfully expressed in Escherichia coli BL21(DE3), with a molecular weight of ~43 kDa, as confirmed by sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis. Substrate specificity assays revealed the highest activity against sodium carboxymethyl cellulose (CMC-Na) (0.861 ± 0.011 U/mg), followed by wheat straw xylan (0.150 ± 0.050 U/mg). RuCel224 exhibited optimal activity at pH 5.0 and 35 °C, retaining over 70% activity between pH 5.0 and 7.0 and 80% activity within the temperature range of 20 to 40 °C. Thermal stability tests showed that RuCel224 retained 80% activity after 30 min at 50 °C. Metal ion analysis demonstrated that Mn²⁺ significantly enhanced RuCel224 activity by 68.5% and 83.1% at 1 mM and 5 mM concentrations, respectively. Hydrolysis efficiency on lignocellulosic substrates revealed the highest reducing sugar release from corn stalk (206.21 ± 19.11 μg/mL), followed by wheat bran (106.63 ± 20.08 μg/mL) and rapeseed straw (93.83 ± 3.57 μg/mL). Overall, RuCel224 is a highly versatile cellulase under mild conditions, demonstrating strong adaptability to agricultural residues. Its superior performance on corn stalk highlights its potential for bioethanol production and other biomass valorization processes.

A novel thermophilic lignocellulolytic bacterium, Geobacillus stearothermophilus TP-3, was isolated and characterized from the Tapovan hot spring in India. The cellulase production of TP-3 was optimized using a One-Factor-at-a-Time (OFAT) approach followed by a Plackett-Burman design, leading to a three-fold enhancement in enzyme yield. Phylogenetic analysis based on 16S rRNA sequencing revealed high sequence similarity with Geobacillus sp. H6a. The cellulase enzyme exhibited optimal activity at 50 °C under alkaline conditions (pH 8.0) and retained ~68% of its activity across a broad temperature range (40-70 °C) for up to three hours, demonstrating remarkable thermo-alkali stability. The ANOVA revealed that three factors-glucose, carboxymethyl cellulose (CMC), and yeast extract-significantly affected cellulase production, with yeast extract emerging as the most influential factor. Notably, TP-3 efficiently degraded agronomic residues, including wheat bran and sugarcane molasses, highlighting its potential for sustainable agricultural waste valorization and bioethanol production. The exceptional thermostability and lignocellulolytic potential of G. stearothermophilus TP-3 position it as a promising candidate for industrial bioconversion processes.

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.

The potential of bioethanol production in marine yeasts and investigation of the optimal conditions of production in the selected isolates

Elaeis guineensis (E. guineensis) oil palm tree (OPT) presented a novel biomass source, with its OPT sap demonstrating the potential for bioethanol production due to its rich sugar content. The increasing waste of the OPT necessitated exploring ways to maximize its utilization and functionality, making bioethanol production a pertinent avenue for sustainable resource utilization. This study aimed to compare the bioethanol yield concentration production in optimized conditions and non–optimized conditions based on response surface methodology (RSM) data from Box–Behnken design (BBD). This study also investigated the viability of felled E. guineensis OPT sap for bioethanol production on the effect of sugar composition and fermentation conditions. Analysis revealed significant variations in fructose, glucose, and sucrose levels across different trunk segments, with sucrose notably higher in some areas. Using Saccharomyces cerevisiae (S. cerevisiae) Kyokai no. 7 in a 2L bioreactor, the study employed repeated batch fermentation to explore the efficiency of bioethanol yield production across 13 cycles under optimized and non–optimized conditions. The optimized fermentation conditions included a felled E. guineensis OPT sap medium with an initial pH of 6.50, supplemented with 6.80 g/L of peptone and 13.28 g/L of corn steep liquor (CSL) at 30°C. The non–optimized conditions were similar but conducted at room temperature. The maximum bioethanol yield concentration of 35.65 g/L, averaging 23–35 g/L per cycle, highlighted the effectiveness and stability of repeated fermentation under optimized conditions, with the bioethanol yield ranging from 3–4 volume/volume percentage (v/v %). The optimized condition significantly improved bioethanol concentration (38.42 %) and volume content (28.67 %), enhancing production efficiency. Bioethanol yield production was markedly improved under optimized conditions, as confirmed by statistical analysis, while non–optimized settings yielded unstable reported data. This research highlighted the importance of controlled environmental conditions and optimized fermentation processes. The study underscored the potential of felled E. guineensis OPT sap as a biomass source for bioethanol, suggesting promising avenues for the scale–up of bioethanol production in the future.

Sweet sorghum has shown great potential as an alternative and promising bioenergy crop that has high potential for bioethanol production due to its high sugar yield, wide adaptability and drought tolerance, thus it is important to continuously evaluate and select most promising lines. Therefore, this study aimed to assess the agronomic performance, cane yield, and ethanol potential of local and exotic sweet sorghum cultivars under rainfed conditions. The experimental design was a randomized complete block design (RCBD) with three replications. Ten various sweet sorghum cultivars were utilized as treatments viz. Theis, Cowley, SSV74, SSV84, BJ248, Suwan sweet extra, Suwan sweet1 and 2, Suphanburi1 and KKU40 (check variety). The results indicated that several cultivars have noteworthy performances, exhibiting higher total soluble solids, such as cv. Suwan sweet extra, KKU40, Suwan sweet2, and Theis, as well as higher cane yield, including Cowley, SSV84, and Suwan sweet extra. Additionally, superior juice yield was observed in cv. SSV84, Suwan sweet1, Suwan sweet extra and Cowley, while higher theoretical ethanol yields were observed in cv. Suwan sweet extra, KKU40, SSV84, and Suwan sweet2. The consideration of grain yield revealed notable performances in cv. SSV84 and Cowley. Conclusively, both cv. SSV84 and Suwan sweet extra exhibited higher cane (46.72 and 44.03 t ha-1, respectively) and ethanol yields (958.1 and 1155.7 l ha-1) in alignment with the objectives of this study. Noteworthy traits were also identified in KKU40, Cowley, and Suwan sweet2. The findings from this study offer valuable insights for future research in this field, particularly in enhancing varietal performance in specific environments and promoting adaptability across diverse conditions.

Exploring Food Waste Potential for Bioethanol Production in Sustainable Energy and Emission Reduction

The future of clean energy: Agricultural residues as a bioethanol source and its ecological impacts in Africa

Abstract As the Philippine bioethanol industry concluded its first decade, it is in due time to assess whether the objectives of the Biofuels Act of 2006 (Republic Act No. 9367) are being met. Specifically, the law aims to reduce the country’s dependence on oil importation, mitigate toxic and greenhouse gases (GHGs), and promote the use of biofuels from indigenous resources to boost the country’s rural economy, by mandating biofuels blending to fossil-based fuels for transport use. This study examined the contribution of seven bioethanol production systems to the country’s climate change mitigation efforts by assessing the environmental impacts, particularly the carbon footprint and GHG emission reduction potential of each bioethanol distillery through life cycle assessment (LCA). Results of the environmental impact assessment revealed that the weighted average carbon footprint of the seven bioethanol production systems is at 1,415.66 gCO2e L−1, which ranges from 287 to 1,726 gCO2e L−1, translating to an average GHG reduction potential of 47.54% or an average avoided GHG of 268,091.15 tons CO2e yr−1 for CY 2019-2020. With the environmental hotspots identified, recommendations were made to improve the distilleries’ carbon footprints, and a sensitivity analysis was conducted to quantify the benefits from the recommended strategies. By applying all strategies, the average GHG reduction potential of the seven bioethanol production systems can get as high as 85.63%, which can be translated to an average avoided GHG of 482,933.91 tons CO2e yr−1.

The present work is to investigate the potential bioethanol production from local vegetable wastes as a possible feedstock via the fermentation process. The waste materials were subjected to a pretreatment process before the fermentation process. Conversion of biomass was performed using cost-effective dry yeast such as Saccharomyces cerevisiae for 5 to 7 days. This research aims to determine bioethanol percentage from vegetable wastes. Besides, the fermented solutions were evaluated and analyzed using variations parameters including sugar content, pH value, and yield during yeast fermentation at 32°C for the production of alcohol. It was noted that the sugar content of the feedstocks used was reduced during the fermentation process, whereas the pH values decreased slightly. The decaying vegetables, including beetroot, carrot, and potatoes, recorded a maximum percentage bioethanol yield of 7%, 5%, and 4.3% respectively. Our work exhibits a promising approach for bioethanol production on a large scale from inexpensive organic wastes and yeast. Furthermore, the bioethanol obtained was blended with pure gasoline to produce ethanol-gasoline blended fuel in various proportions of 0%, 3%, 5%, 7%, 9%, 11%, 13%, and 15%. The resulting alternative fuel characteristics were assessed experimentally using (ASTM) standard methods. The bioethanol-gasoline blend properties including Reid vapor pressure (RVP), density, and Research Octane Number (RON) were measured according to ASTM standard methods. Single-cylinder of spark ignition engine was used to study the impact of ethanol/gasoline blends on engine performance. Overall, the results showed that the RON of gasoline was enhanced remarkably with the increase in ethanol ratio.

Marine macrophytes are considered promising biomass for bioethanol production. The increases in anthropogenic nutrients and climate change have caused unprecedented blooming of ‘sargasso’ across the Atlantic since 2011. This biomass reaches the Caribbean Sea, stranding in large amounts along shorelines, and creating a serious waste management problem. The knowledge of its chemical composition is important to assess whether this material could serve as feedstock for third-generation bioethanol. The beach-cast marine macrophytes collected on the Mexican Caribbean coast in December 2018 were composed of brown seaweeds and a seagrass (23.5 and 76.5% relative abundance, respectively) including Sargassum fluitans, Sargassum natans I, Sargassum natans VIII, Turbinaria turbinata, and the angiosperm Syringodium filiforme. For valorization purposes, glucans, non-glucans carbohydrates and lignin were determined. Besides its abundance, underutilization, and low-cost this whole biomass may have potential as a promising raw material for third-generation bioethanol because it contains easily fermentable glucose such as mannitol (36.3% in whole biomass and 56% in the Sargassum species) and cellulose (36.3% on average). Other specific carbohydrates such as alginate (20–31%) and fucoidan (9.1–8.2%) were present in smaller amounts but they can also be converted to fermentable sugars with the proper methodology. Some advantages and limitations for the potential production of third-generation bioethanol from this biomass are discussed.

Lack of confidence in potential bioenergy production and net benefit hinders rapid implementations of such sustainable energy productions from different waste sources. With the aim of accelerating real-life implementations of more bioenergy productions, this paper presents development of a simple mathematical model, which can be used to evaluate potential bioethanol production capacity from pineapple waste under different input conditions. Based on an earlier experimental study, the mathematical model was developed depending on three contributing factors; pH, temperature and substrate concentration as considered in the earlier experimental study. Results from the developed mathematical formulation were compared with the experimental data from the earlier original study. It is found that the developed model is quite capable to estimate potential bioethanol productions from pineapple waste. Model estimated results are having a coefficient of correlation of 0.84 with the measured data. Standard errors of the model’s estimations are also quite low; RMSE = 0.49, MAE = 0.39 and RAE = 0.06. To facilitate a wider industrial generation, a basic mathematical model framework for economic analysis is proposed involving evaluation of net present values of expected future yields, as well as costs (initial and maintenance). Such mathematical model of economic analysis will help stakeholders on selecting optimum input parameters in achieving targeted benefit through optimised energy consumption.


 
 
 Increasing population growth, industrialization, and the harmful impacts of fossil fuel burning on the environment fascinated the researchers to find a low-cost, environmentally friendly alternative substitute. A potential substitute feedstock for the synthesis of second-generation bioethanol is the lignocellulosic biomass from invasive weedy plants. The aim of this study was to determine the potential of bioethanol production from two weedy plant species using physical, chemical, and physiochemical pretreatment methods, as well as to optimize the pretreatment and culture conditions to obtain a higher reducing sugar amount and ethanol yield. The collected invasive weedy plants, Chromolaena odorata and Tridax procumbens, were cleaned, then pretreated with different acids and bases (4% v/v) at 121oC for 15 min. Then the filtrate was incubated with Saccharomyces cerevisiae (baker‘s yeast) in the peptone yeast extract and nutrient medium (PYN) at room temperature, the pH was maintained at 5.0. T. procumbens plant substrate with the performic acid pretreatment agent produced a significant amount (0.2%) of ethanol, and further studies were conducted with the same substrate and the pretreatment agent. The conditions were optimized successively by changing one factor at a time while keeping the other variables constant. Several important hydrolysis factors were studied for the optimization, including performic acid concentration (0.2–5%), hydrolysis time (10–60 min), fermentation time (24–120 h), inoculum concentration (1.25–7.5 g/100 ml), and rotation speed (50–250 rpm). The maximum ethanol yield of 0.47% was observed at 0.6% performic acid concentration, 30 min of hydrolysis time, 48 h of fermentation time, 5 g/100 ml of inoculum concentration, and 100 rpm rotation speed with T. procumbens using S. cerevisiae.
 Keywords: Bioethanol, Lignocellulosic biomass, Acid hydrolysis, Saccharomyces cerevisiae
 
 

This study aims to separate and characterise indigenous yeast (IY) from tropical fruit waste. The techniques include isolating and characterising yeast from different kinds of fruit waste, testing yeast for ethanol and glucose tolerance, and producing bioethanol in vitro. Using a microscope and visual inspection, the yeast’s morphological identification is done. Using a spectrophotometer to measure optical density, the tolerance tests for glucose and ethanol are used to select yeast biochemically. With the Gas Chromatography-Flame Ionisation Detector (GC-FID), one can measure the amount of ethanol present. Yeast was isolated using selective media to yield six isolates: code A1 from grapes, codes NG1, NG2 from jackfruit, and codes N1, N2, and N3 from pineapple; mango produced no results. Three isolates with the codes A1, NG1, and NG2 were chosen based on test results for resistance to glucose and ethanol. The Saccharomyces cerevisae bioethanol production test yielded 6.60%, 3.30%, 4.5%, and.4.85% of ethanol for the yeast species coded A1, NG1, and NG2, respectively, in terms of ethanol. According to the study’s findings, yeast bearing the NG2 code may be used in the fermentation process to produce bioethanol.

Rice straw (RS), an agricultural residue rich in carbohydrates, has substantial potential for bioethanol production. However, the presence of lignin impedes access to these carbohydrates, hindering efficient carbohydrate-to-bioethanol conversion. Here, we expressed versatile peroxidase (VP), a lignin-degrading enzyme, in Pichia pastoris and used it to delignify RS at 30 °C using a membrane bioreactor that continuously discarded the degraded lignin. Klason lignin analysis revealed that VP-treatment led to 35% delignification of RS. We then investigated the delignified RS by SEC, FTIR, and SEM. The results revealed the changes of RS caused by VP-mediated delignification. Additionally, we compared the saccharification and fermentation yields between RSs treated with and without VP, VP-RS, and Ctrl-RS, respectively. This examination unveiled an improvement in glucose and bioethanol production, VP-RS exhibiting up to 1.5-fold and 1.4-fold production, respectively. These findings underscore the potential of VP for delignifying RS and enhancing bioethanol production through an eco-friendly approach.

Abstract This study investigates the potential for bioethanol production of six types of typical German leftover baked products: bread rolls, pretzel rolls, fine rye bread, white bread, pastry, and cream cakes. The experimental setup consisted of two experiments—one as a control and another with the addition of diammonium phosphate (DAP) to the mash. In terms of monosaccharide concentration at 30% dry matter (DM), white bread mash exhibited the highest level at 251.5 g/L, while cream cakes mash had the lowest at 186 g/L. The highest ethanol production occurred after 96 h of fermentation with rye bread, yielding 78.4 g/L. In contrast, despite having the highest monosaccharide levels, white bread produced only 21.5 g/L of ethanol after 96 h. The addition of DAP accelerated monosaccharide consumption in all baked products, with cream cakes completing the process in just 24 h. Bread rolls, pretzel rolls, pastry, and white bread fermentations finished within 72 h. Ethanol yields significantly increased in three DAP samples, with pretzel rolls yielding the highest ethanol concentration at 98.5 g/L, followed by white bread with 90.6 g/L, and bread rolls with 87.7 g/L. DAP had a substantial impact on all samples, reducing fermentation time and/or increasing ethanol yield. This effect was particularly pronounced with white bread, where it improved conversion efficiency from 17 to 72%, resulting in 90.6 g/L of ethanol. These results demonstrate that waste baked products hold substantial potential for bioethanol production, and this potential can be further enhanced through the addition of DAP. Graphical Abstract