Bioethanol Fermentation Research Articles

A large-area MOF-based membrane for challenging CO2 purification and ethanol/CO2/N2 ternary mixture separation

Bioethanol has garnered widespread attention as a potential substitute for traditional fossil fuels. Focusing on the treatment of bioethanol fermentation exhaust is crucial for optimizing bioethanol recovery and achieving carbon dioxide (CO2) purification. This study successfully achieved the large-scale synthesis of zeolitic imidazolate framework-8 (LSZIF-8), which was then incorporated into polydimethylsiloxane (PDMS) to fabricate large-area ZIF-8/PDMS/PVDF mixed matrix membranes (MMMs) for bioethanol recovery from fermentation exhaust via vapor permeation (VP) processes. The ZIF-8/PDMS/PVDF MMMs exhibited a 1.5-time increase in ethanol permeability and selectivity improved by 1.7 times compared to the PDMS/PVDF membrane. The mass transport behavior of ethanol and CO2 molecules within the membrane, as well as examining the interactions between different components was systematically explored. It delves into the disparities in separation performance between PDMS/PVDF membrane and ZIF-8/PDMS/PVDF MMMs with nitrogen (N2), water vapor as the third component. Notably, high-quality LSZIF-8 crystals serves as a crucial source of raw materials for the continuous preparation of high-performance MMMs, addressing the limitation of traditional nanoparticle fillers in terms of scalability for production. This study paving new avenues for purifying fermentation exhaust and recovering bioethanol, while simultaneously present significant potential for industrial applications.

Bioethanol fermentation integrated with PDMS membrane modified by carbon nanotube and graphene oxide from sugarcane bagasse

Bioethanol fermentation integrated with PDMS membrane modified by carbon nanotube and graphene oxide from sugarcane bagasse

Valorization of process wastes from soft-wheat processing industry through biofuel production.

A substantial amount of process waste is generated during the manufacture of soft-wheat products (SWPs), such as biscuits/cookies, crackers, wafers, and cakes. A small portion of waste is reused in specific biscuits, whereas the rest is usually discarded. This study aimed to investigate the suitability of this waste for the co-production of bioethanol and fatty acid methyl esters (FAMEs or biodiesel). Two groups of waste generated in the SWP industry were included in the study: (a) the waste of low-moisture (<10%) biscuits, crackers, and wafer sheets with no fillings and/or coatings, and (b) the waste of high-moisture (>10%) biscuits, crackers, wafers, and cakes with fillings and/or coatings. The study involved extracting each sample with hexane, and the recovered fat was converted to the FAME through alkali-catalyzed transesterification. The remaining carbohydrate-rich fraction was then converted to bioethanol through amylolytic hydrolysis and yeast fermentation. A great portion (92.42%-93.17%) of the fat was extracted from the wastes and converted to the FAME with adequate yields (13.81-14.55g FAME/g waste, dm) and acceptable conversion efficiencies (85.19%-89.04%). However, bioethanol production from the defatted carbohydrate-rich fractions proceeded rather slowly, yielding only 16.54-18.02 (g ethanol per g of waste, dm), corresponding to fermentation efficiencies ranging from 43.32% to 48.29%. Upon the co-production of FAME and ethanol, a considerable amount (50.93%-53.08%) of waste solids remained in the residue fraction. These findings indicated that production of the FAME with adequate yields and conversion efficiencies is viable from the SWP industry wastes; however, bioethanol yields and fermentation efficiencies are rather limited, which warrants further investigation. PRACTICAL APPLICATION: The soft-wheat processing industry generates 1%-5% of total production as waste. The waste was studied to produce FAME and bioethanol. The fat was extracted from the waste and converted to FAME. Bioethanol yields and fermentation efficiencies are limited due to dough modifiers and antimicrobial additives used in SWP production. Further research is required to improve ethanol yield.

Protein Kinase A Negatively Regulates the Acetic Acid Stress Response in S. cerevisiae.

Bioethanol fermentation from lignocellulosic hydrolysates is negatively affected by the presence of acetic acid. The budding yeast S. cerevisiae adapts to acetic acid stress partly by activating the transcription factor, Haa1. Haa1 induces the expression of many genes, which are responsible for increased fitness in the presence of acetic acid. Here, we show that protein kinase A (PKA) is a negative regulator of Haa1-dependent gene expression under both basal and acetic acid stress conditions. Deletions of RAS2, encoding a positive regulator of PKA, and PDE2, encoding a negative regulator of PKA, lead to an increased and decreased expression of Haa1-regulated genes, respectively. Importantly, the deletion of HAA1 largely reverses the effects of ras2∆. Additionally, the expression of a dominant, hyperactive RAS2A18V19 mutant allele also reduces the expression of Haa1-regulated genes. We found that both pde2Δ and RAS2A18V19 reduce cell fitness in response to acetic acid stress, while ras2Δ increases cellular adaptation. There are three PKA catalytic subunits in yeast, encoded by TPK1, TPK2, and TPK3. We show that single mutations in TPK1 and TPK3 lead to the increased expression of Haa1-regulated genes, while tpk2Δ reduces their expression. Among tpk double mutations, tpk1Δ tpk3Δ greatly increases the expression of Haa1-regulated genes. We found that acetic acid stress in a tpk1Δ tpk3Δ double mutant induces a flocculation phenotype, which is reversed by haa1Δ. Our findings reveal PKA to be a negative regulator of the acetic acid stress response and may help engineer yeast strains with increased efficiency of bioethanol fermentation.

Maximizing biofuel production from algal biomass: A study on biohydrogen and bioethanol production using Mg[sbnd]Zn ferrite nanoparticles

Algal biomass is a promising renewable feedstock for biofuel production that does not compete with food crops or require complex pretreatment like lignocellulosic biomass. This study examined biofuel production from two algae: Alkalinema pantanalense (cyanobacteria) and Chlorella vulgaris (green alga). Although there was no significant difference in their biomass, A. pantanalense showed a higher carbohydrate content (204.96 mg L−1) than C. vulgaris (156.07 mg L−1). To maximize reducing sugar release, three pretreatments were tested: thermotacidic, biological using the new fungal isolate Trichoderma longibrachiatum, and biological with nanoparticles. Biological pretreatment with MgZn ferrite nanoparticles (MZF-nps) at 60 mg L−1 concentration gave the best results, significantly enhancing cellulase, β-glucosidase and filter paper cellulase activities by 20.94 % (A. pantanalense) and 18.63 % (C. vulgaris). For biohydrogen production, the co-culture of Klebsiella pneumoniae and Enterobacter cloacae resulted in faster fermentation and improved hydrogen evolution compared to individual cultures. A. pantanalense and C. vulgaris yields were 35.1 mL g−1 and 26.6 mL g−1 dry weight, with maximal cumulative production of 2478 mL L−1 and 1845 mL L−1, respectively. Optimized Saccharomyces cerevisiae bioethanol fermentation conditions included 72 h incubation, 5 % inoculum, 30 °C, pH 5 under shaking condition, yielded 11.2 g L−1 (A. pantanalense) and 7.2 g L−1 (C. vulgaris). Furthermore, MZF-nps hydrolysate significantly increased bioethanol production, by 4.2-fold (A. pantanalense) to 32.45 g L−1 and 3.48-fold (C. vulgaris) to 28.6 g L−1, compared to thermoacidic pretreatment. In summary, biological pretreatment demonstrates the potential of algal biomass as a renewable feedstock for sustainable biofuel production.

Effect of storage condition on the viability of sago effluents as carbon source in fermentation medium for bioethanol production

In Sarawak, Malaysia, approximately 237 tons/day of sago effluent is commonly discharged into nearby river due to the sago starch extraction process. Due to the high concentration of polymeric compounds, particularly starch, in sago wastewater, which petrifies easily, this condition severely pollutes the environment in the affected area. This study was conducted to determine the viability of using sago effluent as a carbon source and fermentation medium for bioethanol production which indirectly help to minimize the environmental impact as well as the economics of the sago industry. The sago effluent obtained from the local sago mill was analysed for starch content and pH profile while stored at room and cold (4°C) temperature facility. Enzymatic hydrolysis was conducted to convert the residual starch into glucose as carbon source for bioethanol fermentation. Fresh sago effluent can be stored for up to 5 days in cold temperature where the starch content remains constant. The highest starch concentration in sago effluent was 61.33 g/L, in which 50.57 g/L glucose was obtained through the enzymatic hydrolysis process. Hence 82.5% of the starch to glucose conversion yield is revealed. Then, the sago effluent hydrolysate which acts as a carbon source as well as a fermentation medium able to generate 23.14 g/L of bioethanol, displays a 91% theoretical yield of glucose to ethanol. In conclusion, the utilization of sago wastewater as feasible alternative to cheap and locally available and sustainable source of raw materials to produce bioethanol.

Pressure-assisted vacuum filtration fabrication of polymer membranes with enhanced selectivity for the separation of an ethanol/carbon dioxide mixture

The membrane performance and effectiveness of fabrication are significant factors that determine the industrialization of membranes. In this study, a pressure-assisted vacuum filtration method was proposed to fabricate a sub-100 nm thin composite membrane using a homemade polyamide for the separation of an ethanol/carbon dioxide (CO2) mixture. Because during bioethanol fermentation, a large amount of CO2 can be produced, forming fermentation tail gas with vaporized ethanol, which should be separated to recover ethanol and reduce greenhouse CO2 emissions. The fabrication conditions, including the size of the polymer coil and feed pressure, were investigated in detail. Characterization using a dynamic laser scatterometer and low-field nuclear magnetic resonance (NMR) was conducted to reveal the membrane properties. The membrane performance obtained by the pressure-assisted vacuum filtration method was compared with that obtained by the solution casting method, which was demonstrated to be 40 % higher. Meanwhile, when a smaller pore size of the substrate was used, a 56 nm thick composite membrane was obtained with an ethanol/CO2 selectivity of 18 and an ethanol permeance of approximately 35000 GPU (1960 Barrer). Finally, the effects of the operating parameters, such as the feed concentration and stability, on the membrane performance were investigated. This study provides a valuable reference for the fabrication of ultrathin polymer membranes.

Cellulolytic and Ethanologenic Evaluation of Heterotermes indicola's Gut-Associated Bacterial Isolates.

Cellulose is the basic component of lignocellulosic biomass (LCB) making it a suitable substrate for bioethanol fermentation. Cellulolytic and ethanologenic bacteria possess cellulases that convert cellulose to glucose, which in turn yields ethanol subsequently. Heterotermes indicola is a subterranean termite that causes destructive damage by consuming wooden structures of infrastructure, LCB products, etc. Prospectively, the study envisioned the screening of cellulolytic and ethanologenic bacteria from the termite gut. Twenty six bacterial strains (H1-H26) based on varied colonial morphologies were isolated. Bacterial cellulolytic activity was tested biochemically. Marked gas production in the form of bubbles (0.1-4 cm) in Durham tubes was observed in H3, H7, H13, H15, H17, H21, and H22. Sugar degradation of all isolates was indicated by pink to maroon color development with the tetrazolium salt. Hallow zones (0.42-11 mm) by Congo red staining was exhibited by all strains except H2, H7, H8, and H19. Among the 26 bacterial isolates, 12 strains were identified as efficient cellulolytic bacteria. CMCase activity and ethanol titer of all isolates varied from 1.30 ± 0.03 (H13) to 1.83 ± 0.01 (H21) umol/mL/min and 2.36 ± 0.01 (H25) to 7.00 ± 0.01 (H21) g/L, respectively. Likewise, isolate H21 exhibited an ethanol yield of 0.40 ± 0.10 g/g with 78.38 ± 2.05% fermentation efficiency. Molecular characterization of four strains, Staphylococcus sp. H13, Acinetobacter baumanni H17, Acinetobacter sp. H21, and Acinetobacter nosocomialis H22, were based on the maximum cellulolytic index and the ethanol yield. H. indicola harbor promising and novel bacteria with a natural cellulolytic tendency for efficient bioconversion of LCB to value-added products. Hence, the selected cellulolytic bacteria can become an excellent addition for use in enzyme purification, composting, and production of biofuel at large.

Deep eutectic solvent cocktail enhanced the pretreatment efficiency of lignocellulose

Pretreatment of lignocellulosic biomass by breaking down its complex structure is an essential step to facilitate enzymatic hydrolysis of lignocellulose and subsequent bioethanol fermentation. Herein, an eco-friendly pretreatment strategy was developed by applying deep eutectic solvent (DES) cocktail. Attributing to the synergistic effect of two DESs (e.g., betaine-glycerol and choline chloride-oxalic acid (or choline chloride-acetamide)), an impressive 89.51% digestibility for glucan and 75.43% for xylan were achieved. Characterization of pretreated corn stover showed that DES cocktail changed substrate surface structure and enlarged structure pores, which could improve the accessibility of cellulase. The pretreated corn stover was also employed in ethanol fermentation and achieved the yield of 73.35%. Recycling experiments demonstrated the potential reusability of DES cocktail in a sustainable manner towards various biomass sources. These findings highlight the effectiveness and versatility of the developed DES cocktail pretreatment method, paving the way for sustainable bioethanol production from lignocellulosic feedstocks.

Rapid screening of toxicity to thermotolerant yeasts: inhibition of growth and fermentation by ionic liquids and zwitterions

We here established rapid screening methods for toxicity of zwitterions and investigated the toxicity to growth and fermentation.

Sustainable strategies to achieve industrial ethanol titers from different bioenergy feedstocks: scale-up approach for better ethanol yield

Hydrothermal pretreatment is a promising approach to lignocellulosic biomass processing for enzymatic hydrolysis and high-yield bioethanol fermentation, as it reduces downstream inhibitor content and the amount of toxic byproducts generated.

A Study on the Potential of Valorizing Sargassum latifolium into Biofuels and Sustainable Value-Added Products.

To increase the limited commercial utility and lessen the negative environmental effects of the massive growth of brown macroalgae, this work illustrates the feasibility of valorizing the invasively proliferated Sargassum latifolium into different value-added products. The proximate analysis recommends its applicability as a solid biofuel with a sufficient calorific value (14.82 ± 0.5 MJ/kg). It contains 6.00 ± 0.07% N + P2O5 + K2O and 29.61 ± 0.05% organic C. Its nutritional analysis proved notable carbohydrate, ash, protein, and fiber contents with a rational amount of lipid and a considerable amount of beneficial macronutrients and micronutrients, with a low concentration of undesirable heavy metals. That recommends its application in the organic fertilizer, food, medicine, and animal fodder industries. A proposed eco-friendly sequential integrated process valorized its biomass into 77.6 ± 0.5 mg/g chlorophyll, 180 ± 0.5 mg/g carotenoids, 5.86 ± 0.5 mg/g fucoxanthin, 0.93 ± 0.5 mg/g β-carotene, 21.97 ± 0.5% (w/w) alginate, and 16.40 ± 0.5% (w/w) cellulose, with different industrial and bioprocess applications. Furthermore, Aspergillus galapagensis SBWF1, Mucor hiemalis SBWF2, and Penicillium oxalicum SBWF3 (GenBank accession numbers OR636487, OR636488, and OR636489) have been isolated from its fresh biomass. Those showed wide versatility for hydrolyzing and saccharifying its polysaccharides. A Gram-negative Stutzerimonas stutzeri SBB1(GenBank accession number OR764547) has also been isolated with good capabilities to ferment the produced pentoses, hexoses, and mannitol from the fungal saccharification, yielding 0.25 ± 0.014, 0.26 ± 0.018, and 0.37 ± 0.020 g ethanol/g algal biomass, respectively. Furthermore, in a pioneering step for valuing the suggested sequential biomass hydrolysis and bioethanol fermentation processes, the spent waste S. latifolium disposed of from the saccharification process has been valorized into C-dots with potent biocidal activity against pathogenic microorganisms.

Influence of Inhibitors from Microwave Pretreatment of Oil Palm Frond Pulping (OPFP) on Bioethanol Production

This research aims to analyze the influence of inhibitors from microwave pretreatment of oil palm frond pulping (OPFP) on the efficiency of bioethanol fermentation by S.cerevisiae in the simultaneous saccharification and fermentation (SSF) processes. OPFPs were achieved at different ages: 3-4, 4-7, 7-10, 10-20, and 20-25 years old. OPFP was pretreated with a microwave and sulfuric acid (MW/SF), microwave and hydrogen sulfide (MW/HP), and microwave and water (MW/W). The results showed that the main inhibitors formed during the pretreatment process of OPFP were acetic acid, furfural, 5-hydroxymethylfurfural (HMF), furfural, formic acid, and phenol. The pretreatment of OPFP with MW/W had the lowest concentrations of inhibitors compared to the other pretreatment methods. The highest bioethanol yields at all ages of OPFP were in the range of 0.41-0.42 g-bioethanol/g-glucose, corresponding to more than 80% fermentation efficiency. At these conditions, the concentrations of the acetic acid were 0.09-0.19 g/l, HMF =0, furfural =0, formic acid 0.05-0.28 g/l, and phenol 0.22-0.47 g/l. The MW/W was the suitable pretreatment of OPFP for bioethanol production due to the lowest to generate the inhibitor and high ethanol production yield.

Effect of overexpression of partial TDH1 and TDH2/3 gene sequences in a starter strain of industrial bioethanol fermentation on the Brettanomyces bruxellensis contaminant growth.

Selected Saccharomyces cerevisiae strains, such as the commercial Ethanol-Red (ER) strain, are used as starters in the bioethanol industry. Yet, bioethanol fermentations are prone to microbial contaminations, mainly by Brettanomyces bruxellensis and lactic acid bacteria. Chemicals, such as sulphuric acid and antibiotics, are commonly used to combat those contaminations, but they have negative environmental impacts. Recently, ER strain was found to secrete antimicrobial peptides (AMPs) active against B. bruxellensis. Therefore, the partial TDH1 and TDH2/3 genes sequences that codify those AMPs were inserted into the pSR41k plasmid and cloned in ER strains. The relative expression levels (plasmidic/genomic) of those sequences in the respective modified ER strains were quantified by real-time quantitative polimerase chain reaction (RT-qPCR), confirming their overexpression. The effect of the modified strains on B. bruxellensis (Bb) growth was then evaluated during synthetic must (SM) and carob syrup (CS) fermentations, co-inoculated with 105 cells ml-1 of ER and Bb in SM and with 106 of ER and 5×103 cells ml-1 of Bb in CS. Results showed that modified ER strains exerted a much higher inhibitory effect against B. bruxellensis (72-fold in SM and 10-fold in CS) than the non-modified ER strain. In those fermentations, 90-100g l-1 of ethanol was produced in 3-6 days.

Effects of Organic Liquid Waste Derived from Bioethanol Fermentation on Corn Production

The liquid waste (LW) discharged during bioethanol production needs treatment. In this study, LW was applied to corn, and its effects on corn growth, yield, and nitrogen (N) content, as well as on soil chemical properties, were evaluated. Five treatments were applied during corn cultivation: no fertilizer (NF), chemical fertilizer (CF), LW at a standard application rate (LW1.0), LW at 1.7 times the rate of LW1.0 (LW1.7), and split application of LW1.7 (S-LW1.7) in six replications. The amount of N applied was 30 kg 10a−1 for CF and LW1.0, and 51 kg 10a−1 for LW1.7 and S-LW1.7. N was applied separately three times in CF, LW1.0, and LW1.7 and six times in S-LW1.7. A higher corn yield, corn ear weight, and number of leaves was observed in LW treatments than in CF. N content of the corn plant top was higher in S-LW1.7 than in LW1.7; N availability was 56.9% and 40.5% higher, respectively, indicating that split application improved N availability. Soil total N content increased significantly in LW treatments, and soil total carbon content tended to increase in S-LW1.7. Therefore, application of LW could increase corn yield and soil fertility, and its effect could be enhanced by split application.

Synergistic Effects of Torrefaction and Alkaline Pretreatment on Sugar and Bioethanol Production from Wood Waste

Abundant availability of lignocellulosic biomass (LCB) coupled with diverse pretreatment methods have made it a promising option for energy production. However, it faces several challenges, some of which can be overcome by integrating pretreatment processes. The present study aims to optimize the integration of two different pretreatment methods—torrefaction (to reduce moisture content and fractionate biomass) and alkaline pretreatment of wood waste (to delignify biomass)—and utilize it for bioethanol production. Pretreatment performance was evaluated based on delignification, biomass hydrolysis, and bioethanol production. Initially, torrefaction was performed in a continuous reactor at a temperature range of 225–300 °C, followed by optimization of the critical parameters of alkaline pretreatment of torrefied wood waste (TWW), that is, the temperature, reaction time, solid–liquid ratio, and alkali concentration. Subsequently, the chemical and carbohydrate compositions of raw wood waste (RWW) and TWW were studied, followed by enzymatic hydrolysis and bioethanol fermentation. Integrated pretreatment positively impacted the cellulose and glucose contents of raw and torrefied biomass at lower temperatures. The enzymatic hydrolysis of TWW treated with alkali produced higher levels of glucose and bioethanol than (stand-alone) TWW. These results can be used as a basis for choosing the most suitable pretreatment for enhanced biomass conversion.

Bioethanol Production from Non-Conventional Yeasts Wickerhamomyces anomalus (Pichia anomala) and Detection of ADH1 Gene

Bioethanol is an organic compound resulted from the fermentation of sugar substrates by microorganisms which is used as alternative energy sources. During bioethanol fermentation yeast are exposed to various fermentation stresses, including temperature, osmotic, and oxidative stresess. Such conditions may decrease ethanol production. We previously isolated fermentation-stress tolerance yeast isolates from traditional Balinese beverages, identified as Wickerhamomyces anomalus BT2, BT5, and BT6. However no data available regarding the bioethanol production of those isolates. Our study indicates that these strains could utilize various sugar substrates (glucose, xylose, maltose, sucrose) in oxidative fermentative media. The highest value of substrate utilization efficiency following 48 hours fermentation was shown by BT6 on glucose (61.02%), BT 2 on xylose (55.44%) and maltose (60.90%). Measurement of ethanol production by Gas Chromatography showed that the strains were able to produce higher ethanol on the glucose substrate than other substrates. For instance, BT6 could produce the highest ethanol production (5.00 g/L) amongst strains tested by using glucose as substrate. Yet, the particular strains could only produce 0.30 g/L and 0.65 g/L by using xylose and maltose, respectively. For further genetic engineering purposes, we detected ADH1 gene from all three isolates, with high homology to the alcohol dehydrogenase from Saccharomyces cerevisiae, Geobacillus stearothermophilus and Pseudomonas aeruginosa. Further strain development can be carried out targeting the ADH1 gene, important for ethanol fermentation.

Use of Distiller´s Dried Grains with Solubles (DDGS) from corn or wheat in broiler diets

The production of grain-based bioethanol is increasing due to the rising demand for biofuels and the global decline in fossil fuel sources. Distiller’s dried grains with solubles (DDGS) from corn or wheat are the main by-product of bioethanol fermentation, primarily through dry milling technology, and have been used as low-cost animal feed. With the increase in ethanol production from grains, the production of DDGS from corn or wheat also increases. Several studies have found that DDGS has high nutritional value but variable composition, and researchers have found ways to enhance its quality and safety. Various approaches have been proposed to improve the digestibility and nutritional value of DDGS. However, despite its high nutritional value, DDGS has not yet been fully studied and is less utilized in broiler feeding. The benefits and risks associated with the use of DDGS have been studied for a long time, but more research is needed to establish quality and safety standards for DDGS. This review aims to highlight the challenges of using DDGS in broiler chicken nutrition.

Novel endolysin LysMP for control of Limosilactobacillus fermentum contamination in small-scale corn mash fermentation

BackgroundTraditional bioethanol fermentation industries are not operated under strict sterile conditions and are prone to microbial contamination. Lactic acid bacteria (LAB) are often pervasive in fermentation tanks, competing for nutrients and producing inhibitory acids that have a negative impact on ethanol-producing yeast, resulting in decreased yields and stuck fermentations. Antibiotics are frequently used to combat contamination, but antibiotic stewardship has resulted in a shift to alternative antimicrobials.ResultsWe demonstrate that endolysin LysMP, a bacteriophage-encoded peptidoglycan hydrolase, is an effective method for controlling growth of LAB. The LysMP gene was synthesized based on the prophage sequence in the genome of Limosilactobacillus fermentum KGL7. Analysis of the recombinant enzyme expressed in E. coli and purified by immobilized metal chelate affinity chromatography (IMAC) showed an optimal lysis activity against various LAB species at pH 6, with stability from pH 4 to 8 and from 20 to 40 °C up to 48 h. Moreover, it retains more than 80% of its activity at 10% ethanol (v/v) for up to 48 h. When LysMP was added at 250 µg/mL to yeast corn mash fermentations containing L. fermentum, it reduced bacterial load by at least 4-log fold compared to the untreated controls and prevented stuck fermentation. In comparison, untreated controls with contamination increased from an initial bacterial load of 1.50 × 107 CFU/mL to 2.25 × 109 CFU/mL and 1.89 × 109 CFU/mL after 24 h and 48 h, respectively. Glucose in the treated samples was fully utilized, while untreated controls with contamination had more than 4% (w/v) remaining at 48 h. Furthermore, there was at least a fivefold reduction in lactic acid (0.085 M untreated contamination controls compared to 0.016 M treated), and a fourfold reduction in acetic acid (0.027 M untreated contamination controls vs. 0.007 M treated), when LysMP was used to treat contaminated corn mash fermentations. Most importantly, final ethanol yields increased from 6.3% (w/v) in untreated contamination samples to 9.3% (w/v) in treated contamination samples, an approximate 50% increase to levels comparable to uncontaminated controls 9.3% (w/v).ConclusionLysMP could be a good alternative to replace antibiotics for mitigation of LAB contamination in biofuel refineries.

Performance of combined hydrochemo-mechanical pretreatment of rice straw for bioethanol production

Pretreatment was an inevitable process in the biorefinery process of lignocellulosic biomass utilization. Generally, biomass was considered an essential carbon source that could be converted into several bio-based products such as biofuels and biochemicals. This study aimed to evaluate the performance of combined hydrochemo-mechanical pretreatment of rice straw for bioethanol production. Rice straw was pretreated with autoclave followed by ball-milling pretreatment. The hydrochemical pretreatment was performed in an autoclave with different concentrations of NaOH (1 and 10%) at 121 °C for two different durations (30, 60 min). The pretreated biomasses were then subjected to ball-milling pretreatment for size reduction and subsequently hydrolyzed via enzymatic and bioethanol fermentation. The obtained results indicated that the highest reducing sugars were 0.4513 kg reducing sugar/kg biomass obtained by 1% of NaOH at 121 °C, 30 min, which provided the highest energy efficiency and the lowest waste generation was 0.1423 kg reducing sugar/kWh and 0.2570 kg of waste/kg reducing sugar respectively. Moreover, the highest bioethanol yield was 0.0491 kg/kg biomass obtained from a similar condition. Additionally, the combined pretreatment suggested that it could be an alternative pretreatment for a lignocellulosic biorefinery in industrial applications.