Ethanol Production Research Articles

Sustainable waste management: a comprehensive life cycle assessment of bioethanol production from agricultural and municipal waste.

Biofuels have emerged as a promising and eco-friendly alternative to conventional fossil fuels. Biofuel sourced from rice straw (RS) and municipal solid waste (MSW), which are abundant residues from agricultural and municipal activities, present a sustainable solution to address waste management challenges. Utilizing life cycle assessment, this study quantifies the environmental advantages by assessing the reduction in greenhouse gas emissions, energy consumption, and other environmental impacts linked with employing these waste materials for biofuel production. Employing a cradle-to-gate approach as the system boundary for bioethanol production, with the functional unit set as per liter of bioethanol produced, the analysis reveals that the global warming potential (GWP) for ethanol from MSW is 4.4 kg CO2 eq., whereas for RS, it is 2.1 kg CO2 eq. per functional unit. The total environmental impacts were primarily due to enzymatic hydrolysis and electricity consumption for ethanol production from MSW and RS. Despite advancements, fossil fuel consumption remains a potential energy source for biofuel production. The cumulative energy demand stands at 18.6 MJ for RS and 71.5 MJ for MSW per functional unit, underscoring the potential to significantly reduce overall impacts by transitioning to a more environmentally sustainable energy source. The uncertainty analysis acknowledges the inherent uncertainties associated with data, assumptions, and methodologies, highlighting the crucial need for ongoing research and updates to enhance the accuracy of future assessments. This analysis forms the foundation for well-informed decision-making, providing valuable insights for policymakers, industry stakeholders, and consumers.

Cellulosic Ethanol Production from High-Solids Corncob Residues by Simultaneous Saccharification and Fermentation on a Pilot Scale

Cellulosic Ethanol Production from High-Solids Corncob Residues by Simultaneous Saccharification and Fermentation on a Pilot Scale

Development of a Zn-Based Single-Atom Nanozyme for Efficient Hydrolysis of Glycosidic Bonds.

Hydrolytic enzymes are essential components in second-generation biofuel technology and food fermentation processes. Nanozymes show promise for large-scale industrial applications as replacements for natural enzymes due to their distinct advantages. However, there remains a research gap concerning glycosidase nanozymes. In this study, a Zn-based single-atom nanozyme (ZnN4-900) is developed for efficient glycosidic bond hydrolysis in an aqueous solution. The planar structure of the class-porphyrin N4 material approximatively mimicked the catalytic centers of natural enzymes, facilitating oxidase-like (OXD-like)activity and promoting glycosidic bond cleavage. Theoretical calculations show that the Zn site can act as Lewis acids, attacking the C─O bond in glycosidic bonds. Additionally, ZnN4-900 has the ability to degrade starch and produce reducing sugars that increased yeast cell biomass by 32.86% and ethanol production by 14.56%. This catalyst held promising potential for enhancing processes in ethanol brewing and starch degradation industries.

A High-Quality Mixed Matrix Membrane with Nanosheets Assembled and Uniformly Dispersed Fillers for Ethanol Recovery.

A high-quality filler within mixed matrix membranes, coupled with uniform dispersity, endows a high-efficiency transfer pathway for the significant improvement on separation performance. In this work, a zeolite-typed MCM-22 filler is reported that is doped into polydimethylsiloxane (PDMS) matrix by ultrafast photo-curing technique. The unique structure of nanosheets assembly layer by layer endows the continuous transfer channels towards penetrate molecules because of the inter-connective nanosheets within PDMS matrix. Furthermore, an ultrafast freezing effect produced by fast photo-curing is used to overcome the key issue, namely filler aggregation, and further eliminates defects. When pervaporative separating a 5 wt% ethanol aqueous solution, the resulting MCM-22/PDMS membrane exhibits an excellent membrane flux of 1486g m-2 h-1 with an ethanol separation factor of 10.2. Considering a biobased route for ethanol production, the gas stripping and vapor permeation through this membrane also shows a great enrichment performance, and the concentrated ethanol is up to 65.6 wt%. Overall, this MCM-22/PDMS membrane shows a high separation ability for ethanol benefited from a unique structure deign of fillers and ultrafast curing speed of PDMS, and has a great potential for bioethanol separation from cellulosic ethanol fermentation.

Advanced temperature control in ethanol fermentation using a PSO-PID controller with split-range control strategy

Global energy demand is experiencing a notable surge due to growing energy security. Renewable energy sources, like ethanol, are becoming more viable. In the present study, the application of a PSO-PID (Particle Swarm Optimization – Proportional Integral Derivative) controller with a split-range control strategy was suggested for the regulation of temperature within the fermentation system. To optimize performance, a POS-PID controller with a split-range arrangement utilizing two control valves for hot and cold utilities was constructed. The study began by examining the open-loop dynamic response of the system to inlet temperature and concentration disturbances during ethanol production fermentation. Subsequently, a transfer function model was developed through linearization at the steady-state operating point. The split-range controller structure, implemented by optimizing the PSO-PID controller parameters using PSO, effectively demonstrated temperature control in simulations of a nonlinear model. In this investigation, the ethanol fermentation system was modeled as a CSTR using a modified Monod equation for microbial growth kinetics. Various dynamic behavioral disturbances were explored and verified in the model with plant data in this study. The simulation model results were validated through plant data. The proposed method showed superior closed-loop performance with respect to errors, with the actuators proving to be effective than other reported methods for temperature control.

Use of spent yeasts from bioethanol production plant as low-cost nitrogen sources for ethanol fermentation from sweet sorghum stem juice in low-cost bioreactors

Two spent yeasts from an ethanol production plant, spent yeast after distillation (SY-AD) and spent yeast after fermentation (SY-AF), were used as low-cost nitrogen sources for ethanol fermentation from sweet sorghum stem juice (SSJ) by a commercial dry yeast (Saccharomyces cerevisiae) in air-locked flasks. SY-AF was the more effective nitrogen source for ethanol fermentation, giving ethanol concentration (PE) and ethanol productivity (QE) values of 95.22 g/L and 1.98 g/L·h, respectively. When SY-AF was disrupted by autolysis, and the spent yeast hydrolysate (SYH) obtained was used as a nitrogen supplement. It was found that ethanol production in terms of PE and QE values increased to 102.20 g/L and 2.83 g/L·h, respectively. When three bioreactors, a stirred-tank bioreactor (STR, a typical bioreactor), a column bioreactor with stirrer (CS-R, a tower bioreactor) and an external loop bioreactor (ELR, a low-cost bioreactor with no agitation), were used for ethanol production from the SSJ supplemented with SYH, the fermentation efficiencies of all bioreactors were not different. Appropriate aeration during fermentation (0.31 vvm for 12 h) in the three bioreactors could enhance the QE value, reaching 3.36 g/L·h. Both the CR-S and ELR could be successfully used for ethanol production from SSJ supplemented with SYH.

High-efficiency conversion of corn bran to ethanol at 150 L scale

Fractionated corn bran was processed to maximize ethanol production from starch, cellulose, and xylan. After various bench-scale experiments, an optimized process with dilute acid pretreatment (1.5 % w/w H2SO4) at 90 °C for 60 min was utilized followed by enzymatic hydrolysis using cellulase and hemicellulase for 48 hr. After simultaneous saccharification (regarding starch) and fermentation at 150 L using an engineered yeast, which consumes both glucose and xylose to make ethanol, the 86 % total sugar conversion yield was achieved, including conversions of 95 % for starch, 77 % for cellulose and 77 % for xylan. Also, an accurate mass balance was formulated for ethanol-producing carbohydrates including starch, cellulose, and xylan from feedstock to final ethanol. A highly efficient process of converting corn fiber to ethanol was successfully scaled up to 150 L.

Did the entry of the corn ethanol industry in Brazil affect the relationship between domestic and international corn prices?

AbstractThis study investigates the relationship between corn prices in Brazil and the international market, considering a rise in corn ethanol production in Brazil's Midwest region since 2017. Did the entry of the corn ethanol industry in Brazil affect the relationship between domestic and international corn prices? A cointegration analysis was made with a monthly time series from May 2005 to August 2023 controlling for different exogenous events or shocks that may have affected global agricultural markets. The study's findings indicate a stable long‐term relationship between the international and Brazilian corn prices, with changes in international prices being predictors of variations in Brazilian domestic prices, while the opposite was not statistically supported. The study also found no evidence to support the claim that the entry of the corn ethanol industry into Mato Grosso state in 2017 impacted the prices paid to local producers. Therefore, the increase in Brazilian corn prices cannot be attributed to additional demand for corn by local mills, an important result that contributes to discussions such as food versus fuel and indirect land use change.

Reduction of sugarcane stillage generation through Heat-Integrated Distillation and Evaporation (HIDiE)

Sugarcane stillage, or vinasse, is the most voluminous byproduct generated in ethanol production, with an average volume ratio of 12:1. Fertigation is the simplest worldwide destination for stillage, but stricter environmental regulations require its distribution over wider areas to avoid soil oversaturation, demanding thus expensive transportation infrastructure. While reducing disposed stillage is critical, current concentration systems are inefficient and require additional energy (steam) and dedicated evaporators, which are prohibitively expensive for most installed industries. This study demonstrates, through performance comparisons with conventional distillation systems (CS), that a novel system, here denoted as HIDiE (Heat-Integrated Distillation and Evaporation), efficiently reduces the volume of stillage still during the stripping step, requiring no additional equipment and resulting in a leaner and cheaper approach. Process simulations in ASPEN Plus V11 software were used to validate premises using thermodynamic analysis and mass and energy balances. HIDiE produces significantly less stillage (1.7 - 7.8 m3/ m3ethanol) than CS (5.4 - 14.5 m3/ m3ethanol) under same steam consumption. Using HIDiE for wine with alcoholic grades ranging from 6 to 14 %v/v can result in gains of 45.7–69.3 %. This novel process concept contributes to the expansion of the economic radius for stillage fertigation, implying significant savings for the industry and the environment.

Utilization of local corn (Zea Mays) wastes for bioethanol production by separate hydrolysis and fermentation

Maize is the second most-common crop globally. Thus, enormous maize cobs are generated annually from maize processing activities which could serve as a potential and non-edible source for biofuel production. The primary aim of this research was to assess the practicality of producing bioethanol from discarded maize cob through a distinct two-step process referred to as separate hydrolysis and co-fermentation. After a 72-hour fermentation period, the greatest ethanol yield of 66.23 ± 8.35 mL/kg was obtained. This was followed by 54.33 ± 7.27 35 mL/kg after 48 h, and 21.68 ± 2.97 35 mL/kg after 24 h. Importantly, all ethanol yields at different time points exhibited statistical significance at p < 0.05. Moreover, the study revealed a robust positive correlation (r = 0.99, p < 0.01) between glucose and Total reducing Sugars (TRS) yields, and negative correlations were observed between ethanol yield and glucose (r = -0.97, p < 0.05) as well as ethanol and TRS (r = -0.98, p < 0.05). The results indicate the potential of maize cob waste as a valuable resource for bioethanol production. Significant enhancements in operational processes are necessary to enhance the economic feasibility of producing ethanol from maize cobs. Nigeria's utilization of waste for biofuel production is bolstered by substantial policy and financial backing for renewable fuels. The economic viability of ethanol production from maize cobs relies heavily on its competitiveness relative to other waste treatment methods and the effectiveness of policy measures.

Harnessing Ulva ohnoi for eco-friendly bioethanol production via hydrothermal pretreatment

BackgroundThe increasing demand for renewable energy sources has sparked interest in biofuels derived from green seaweeds, owing to their abundance and high carbohydrate content. Ulva ohnoi, harvested from Taiwan's shores, presents a promising candidate for bioethanol production due to its favorable characteristics. MethodsIn this study, Ulva ohnoi underwent hydrothermal pretreatment at temperatures of 120 °C, 150 °C, and 180 °C for 20 min. The pretreated slurry obtained at 180 °C was subjected to enzymatic saccharification at pH 4.8 and 50 °C for 72 h. This process resulted in the production of 5.8 g/L of glucose, which was subsequently concentrated to 18.86 g/L. Significant FindingsFermentation of the concentrated sugar fractions using Saccharomyces cerevisiae WLP 300 at 30 °C for 24 h yielded remarkable ethanol yields of 0.39 and 0.43 g/g of sugar. These yields approached the maximum theoretical values of 76.1% and 84.58%, respectively. Additionally, the study reported a maximum ethanol productivity of 0.54 g/L/h in the 12th hour in the concentrated fraction. These findings underscore the potential of Ulva ohnoi as a sustainable biofuel and clean energy source, aligning with Sustainable Development Goal 7 (SDG 7) of ensuring access to affordable, reliable, sustainable, and modern energy for mankind.

Energy assessment and heat integration of biofuel production from bio-oil produced through fast pyrolysis of sugarcane straw, and its upgrading via hydrotreatment

Sugarcane processing is one of the most important economic activities in Brazil, producing ethanol and sugar for domestic and international markets. Utilising the lignocellulosic residues of this industry, specifically bagasse and straw, would increase the second-generation biofuel production without increasing the sugarcane planted area. Among the processes available, the fast pyrolysis is a thermochemical conversion process that produces mainly bio-oil, a liquid with several advantages over solid biomass, regarding transportation, pumping, storage, and handling. Moreover, the bio-oil can be upgraded to obtain biofuels of higher added-value. Among feasible upgrading technologies, the hydrotreatment is one of the most promising methods for eliminating the reactive functionalities of the bio-oil by removing oxygen or cracking large molecules in the presence of hydrogen; however, this comes at the expense of a significant hydrogen consumption. Thus, the aim of this study is to evaluate the biofuel production through the fast pyrolysis of sugarcane straw, followed by the upgrading of the produced bio-oil via hydrotreatment. The evaluation is carried out by way of energy and mass balances of the processes, performed using the software Aspen Plus. Furthermore, the possibilities of integrating the bio-oil production and upgrading into the conventional ethanol and sugar production process will also be assessed through heat integration, applying the Pinch analysis. Results showed the potential for renewable gasoline and diesel production with yields of 0.086 kg/kg of dry straw and 0.08 kg/kg of dry straw, respectively. Additionally, integrating the pyrolysis process, including the bio-oil upgrading, into the ethanol production process can achieve a liquid fuel production (ethanol, gasoline and diesel) of 2289.8 MJ/t cane, which represents an increase of 29 %, while the surplus electricity increases in 5.3 %, when compared to the conventional ethanol production plant.

Incorporation anthracene and Cu to NH2-Zr-UiO-67 metal-organic framework: Introducing the simultaneous selectivity and efficiency in photocatalytic CO2 reduction to ethanol

Metal-organic frameworks (MOFs) are considered promising candidates for photocatalytic CO2 reduction (PCR) into valuable organic fuels. However, compared to numerous reports regarding CO, CH4, and CHOOH generation, the explored MOFs have shown limited success in producing alcohols, particularly EtOH, through the PCR strategy. Existing MOFs also suffer from insufficient selectivity and efficiency. This study addresses these limitations by implementing a dual modification strategy on NH2-Zr-UiO-67 MOFs. This strategy involves synthesizing four MOF derivatives with different ratios of redox-active metal sites (Cu) to light absorption antenna (anthracene): 1:1, 2:1, 1:2, and 1:3. The as-synthesized MOFs (denoted as Cu/An (X:X)@NZU67 exhibited a remarkable capability for PCR-to-EtOH, without requiring a photosensitizer. The optimal amount of anthracene plays a crucial role in several aspects: improving light absorption, enhancing CO2 adsorption capacity, and promoting charge transfer/separation. Efficient charge transfer is critical for facilitating the multi-step electron transfer pathway required for ethanol synthesis. Notably, Cu/An (1:2)@NZU67 achieved an ethanol productivity of 624.17 µmolh−1g−1 for EtOH, which is, to the best of our knowledge, the highest efficiency reported for MOFs in PCR-to-EtOH conversion so far. Besides significant performance, the MOF showed 100% selectivity for EtOH production. This work represents a significant milestone in the field of PCR-to-EtOH transformation by providing a new perspective for designing MOF photocatalysts that can simultaneously improve both selectivity and efficiency.

Multi-stage process for mixed microbial culture production of polyhydroxyalkanoates from sugarcane stillage: Assessment of external nutrient supplementation

Sugarcane stillage is an abundant wastewater from ethanol production. It has drawn considerable interest as a potential feedstock for biotechnological processes aiming at the recovery of energy and value-added products. In this study we explored the use of stillage for the production of polyhydroxyalkanoates (PHA), which are microbial bioplastics with potential to replace conventional plastics in specific applications. As stillage is nutrient deficient, we investigated the impact of external nutrient supplementation on the selection of PHA-producing mixed cultures. Cultures selected under four different total-chemical-oxygen-demand-to-nitrogen ratios (COD.t/N) (15, 30, 40 and 80) were evaluated according to their PHA production performance and microbial composition. The experimental results demonstrated that the most favorable PHA production was achieved for the biomass selected under strict carbon-limiting conditions, with a COD.t/N ratio of 15. This resulted in an overall PHA volumetric productivity of 2.10 g PHA L−1 d−1, a maximum intracellular PHA content of 0.65 g PHA g VSS−1 and a PHA storage yield of 0.71 g CODPHA g CODH.Org−1. The resulting PHA was a copolymer of 3-hydroxybutyrate (73 %mol) and 3-hydroxyvalerate (27 %mol) monomers. The microbial consortium was enriched by members of the Brevundimonas genus, known PHA producers, with a relative abundance of 26.4 %.

Advancements in High Gravity Fermentation Strategies for Optimizing Ethanol Production from Sugarcane-Based Substrates

Advancements in High Gravity Fermentation Strategies for Optimizing Ethanol Production from Sugarcane-Based Substrates

High-quality draft genome sequence of Paenibacillus sp. RC80, a candidate for biofuel production.

Paenibacillus sp. RC80 was isolated from temperate deciduous forest soil in New England. The assembled genome is a single contig with 5,977,337 bp and 97.15% estimated completion. RC80 contains features for 2,3-butanediol dehydrogenase production and pathways involved in ethanol production.

Differential impacts of furfural and acetic acid on the bioenergetics and fermentation performance of Scheffersomyces stipitis

Lignocellulosic material is a leading carbon source for economically viable biotechnological processes; however, compounds such furfural and acetic acid exhibit toxicity to yeasts. Nonetheless, research about the molecular mechanism of furfural and acetic acid toxicity is still scarce in yeasts like Scheffersomyces stipitis. Thus, this study aims to elucidate the impact of furfural and acetic acid on S. stipitis regarding bioenergetic and fermentation parameters. Here, we provide evidence that furfural and acetic acid induce a delay in cell growth and extend the lag phase. The mitochondrial membrane potential decreased in all treatments with no significant differences between inhibitors or concentrations. Interestingly, reactive oxygen species increased when the inhibitor concentrations were from 0.1 to 0.3 % (v/v). The glycolytic flux was not significantly (p > 0.05) altered by acetic acid, but furfural caused different effects. Ethanol production decreased significantly (4.32 g·L-1 in furfural and 5.06 g·L-1 in acetic acid) compared to the control (26.3 g·L-1). In contrast, biomass levels were not significantly different in most treatments compared to the control. This study enhances our understanding of the effects of furfural and acetic acid at the mitochondrial level in a pentose-fermenting yeast like S. stipitis.

Enhanced reducing sugar production by blending hydrolytic enzymes from Aspergillus fumigatus to improve sugarcane bagasse hydrolysis.

Biomass pretreatment for the production of second-generation (2G) ethanol and biochemical products is a challenging process. The present study investigated the synergistic efficiency of purified carboxymethyl cellulase (CMCase), β-glucosidase, and xylanase from Aspergillus fumigatus JCM 10253 in the hydrolysis of alkaline-pretreated sugarcane bagasse (SCB). The saccharification of pretreated SCB was optimised using a combination of CMCase and β-glucosidase (C + β; 1:1) and addition of xylanase (C + β + xyl; 1:1:1). Independent and dependent variables influencing enzymatic hydrolysis were investigated using response surface methodology (RSM). Hydrolysis using purified CMCase and β-glucosidase achieved yields of 18.72mg/mL glucose and 6.98mg/mL xylose. Incorporation of xylanase in saccharification increased the titres of glucose (22.83mg/mL) and xylose (9.54mg/mL). Furthermore, characterisation of SCB biomass by scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy respectively confirmed efficient structural disintegration and revealed the degree of crystallinity and spectral characteristics. Therefore, depolymerisation of lignin to produce high-value chemicals is essential for sustainable and competitive biorefinery development.

A Genomewide Evolution-Based CRISPR/Cas9 with Donor-Free (GEbCD) for Developing Robust and Productive Industrial Yeast.

Developing more robust and productive industrial yeast is crucial for high-efficiency biomanufacturing. However, the challenges posed by the long time required and the low abundance of mutations generated through genomewide evolutionary engineering hinder the development and optimization of desired hosts for industrial applications. To address these issues, we present a novel solution called the Genomewide Evolution-based CRISPR/Cas with Donor-free (GEbCD) system, in which nonhomologous-end-joining (NHEJ) repair can accelerate the acquisition of highly abundant yeast mutants. Together with modified rad52 of the DNA double-strand break repair in Saccharomyces cerevisiae, a hypermutation host was obtained with a 400-fold enhanced mutation ability. Under multiple environmental stresses the system could rapidly generate millions of mutants in a few rounds of iterative evolution. Using high-throughput screening, an industrial S. cerevisiae SISc-Δrad52-G4-72 (G4-72) was obtained that is strongly robust and has higher productivity. G4-72 grew stably and produced ethanol efficiently in multiple-stress environments, e.g. high temperature and high osmosis. In a pilot-scale fermentation with G4-72, the fermentation temperature was elevated by 8 °C and ethanol production was increased by 6.9% under the multiple stresses posed by the industrial fermentation substrate. Overall, the GEbCD system presents a powerful tool to rapidly generate abundant mutants and desired hosts, and offers a novel strategy for optimizing microbial chassis with regard to demands posed in industrial applications.

Biochemical and Biorefinery Platform for Second-Generation Bioethanol: Fermentative Strategies and Microorganisms

Bioethanol is the most commonly used biofuel. It is an alternative to replace fossil fuels in renewable energy; it can be produced from lignocellulosic feedstock using a biotechnological process. Their participation of microorganisms is crucial in the bioconversion process of fermentation for ethanol production and can involve bacteria, fungi, and yeasts. However, when working within bioethanol processes from lignocellulose feedstock, microorganisms face some challenges, such as high temperature, high solids content, and the ability to ferment sugars for high ethanol concentration. Such challenges will depend on operative strategies, such as simultaneous saccharification and fermentation, separate hydrolysis and fermentation, semi-simultaneous saccharification and fermentation, and consolidated bioprocessing; these are the most common configurations. This review presents different trends of the microbial role, biochemical application, and fermentation operative strategies for bioethanol production of the second generation.