Acid Fermentation Research Articles

Effects of ethanol addition on caproic acid production and rumen microorganism community structure from straw fermentation

In order to enhance caproic acid concentration from wheat straw fermentation and elucidate the microbial community inside the system. This study investigated ethanol addition with different mode for wheat straw co-cultured with rumen fluid. The results showed that segmentation addition of ethanol resulted in a higher caproic acid of 1473 mg/L. The structural characteristics of the microorganism community were further analyzed to reveal the functional of microorganisms in the acid fermentation from straw. Among them, Prevotella had a strong hemicellulose degradation capacity; Corynebacterium, Ureibacillus, and Clostridium_sensu_stricto_12, were correlated with the increasing trend of caproic acid. Control the proper ethanol concentration and optimum fermentation conditions would avoid the biotoxicity for the microorganisms and enhance the product yield.

Optimization of dissolution and fermentation acid production of rhamnolipid-alkali-heat synergistic pretreatment of sludge

With the development of the urban sewage treatment industry, the sludge output has increased year by year, and it has the characteristics of large output and high organic content, and has great potential for resource recovery. However, the biodegradability of sludge is poor, resulting in low added value of resource products. Therefore, it is necessary to treat sludge efficiently and improve the utilization. Based on this, the effects on sludge characteristics and acid-producing fermentation were investigated, and optimal conditions were determined by response surface method. The results showed that: The optimal conditions for experimental optimization are rhamnolipid (RL: 40 mg/gVS) alkali (Alk: 35 mg/gVS), heat: 80 °C. Response surface design optimization results are RL (28.44 mg/gVS), NaOH (35 mg/gVS), heat: 80 °C. In the process of RL-Alk-Heat pretreatment, the organic matter dissolution is Heat > Alk. Also, RL, Alk and Heat all promoted the content of fluorescent substances. From the results of the optimal combination verification test, it showed that SC (Soluble carbohydrate) and SP (Soluble protein) increase. Among them, three-factor treatment is higher than two-factor treatment than single-factor treatment.

Comparison of Saccharification And Lactic Acid Production Efficiencies From Chemically and Biologically Pretreated Wheat Straw

Background In recent times, agricultural waste has been utilized in many industries as an energy source in several processes. Wheat straw, one of the most cost-effective raw material, has a great potential to be utilized as a substrate in fermentation to produce lactic acid. Utilization of agro waste material as the carbon source provides a cheap and environment friendly production of lactic acid. Methods A comparison of chemical and biological pretreatment of wheat straw and the use of pretreated wheat straw hydrolysate in fermentation of Lactobacillus was carried out using optimized process parameters of temperature and ph. Pretreatment methods using dilute acid and white rot fungus Coriolis versicolor were performed on wheat straw as well as the effect of copretreatment with calcium hydroxide on differentially pretreated wheat straw was studied by analyzing sugar and lactic acid concentrations during fermentation. The effect of different pH (7, 8, and 9) on fermentation using dilute acid pretreated wheat straw was observed to lower the lactic production with the increase in ph. Dilute acid pretreatment of wheat straw provided the highest concentration of glucose at 57.2mg/L and subsequently enhanced yield of lactic acid during fermentation while the biologically pretreated wheat straw hydrolysate provided comparatively lower concentration of glucose at 49.2mg/L and thus decreased lactic acid production. Result The final lactic acid concentration of 48.14 mg/L was obtained in dilute acid pretreated wheat straw with Yp/s of 0.915 mg/mg, while the use of biologically pretreated wheat straw hydrolysate provided 39.56 mg/L concentration of lactic acid and an Yp/s of 0.908 mg/mg. However, a reduced lactic acid concentration of 27.03 mg/L and 20.62 mg/L was seen after the co-pretreatment of both dilute acid and fungal pretreated wheat straw with calcium hydroxide respectively, indicating its adverse effects on fermentation process. Conclusion Pretreatment of wheat straw with dilute acid can be considered a good saccharification method to obtain the optimum concentration of lactic acid in microbial fermentation carried out at optimum temperature and pH conditions.

Numerical Modelling and Optimization of Bioethanol Concentration Produced from Local Sawdust following Response Surface Methodology

This work studies the modelling and optimization of bioethanol production from locally sourced saw dust waste. The saw dust samples are obtained from common wood species in the Nigerian tropical rain forest. Nigeria is one of the producers of wooden products in the world. Many species of wood can be found in Nigeria’s tropical rain forest. Some of the most common wood species include; Astonia boonei (duku), Bombax bounopozense (West African bombax), Brachystegia eurycoma (Okwen), Terminalia superba (White afara). Sawdust samples were obtained from a local saw mill in Edo State, Nigeria. The samples were pre-treated, hydrolyzed, fermented and the bioethanol distilled out. Optimization of bioethanol was performed by using Central Composite design of response surface methodology. Four variables such as acid concentration, hydrolyzing time, hydrolysis temperature and fermentation time were considered as influencing factors on the yield of bioethanol. The optimization of ethanol was investigated in this study under the following conditions: acid concentration (0.5-2.5 %w/w), hydrolysis temperature (100-130 °C), hydrolysis time (10-50 minutes) and fermentation time (2-6 days). It was observed from the statistical analysis that the maximum ethanol yield of 24.85 % (g/L) was obtained at optimum acid hydrolysis of acid concentration 2.0 %w/w, Hydrolysis time 40 minutes, Hydrolysis temperature 122.50 °C, and Fermentation time 5 days.

Mechanism of Electron Acceptor Promoting Propionic Acid Transformation in Anaerobic Fermentation

To improve the conversion efficiency of propionic acid in the post-anaerobic fermentation of biogas slurry, the anaerobic fermentation process using biogas slurry with a high acid content was simulated in an anaerobic reactor at 35 ± 0.5 °C using sodium propionate as the sole substrate. The effects of different electron acceptors (NO3−, SO42− and Fe3+) on propionic acid conversion and the succession of microbial community structures were investigated. The results showed that the experimental group with the electron acceptor NO3− exhibited the best anaerobic fermentation effect, with a maximum propionate removal rate of 94%, which was 36% higher than the control group without an electron acceptor. The maximum methane production rate was 307.6 mL/g COD, an increase of 30% compared with the control group. Thauera, Aquabacterium, Desulfomicrobium, Clostridium_sensu_stricto_1, and other functional microorganisms were all enriched. The dominant functional genes related to redox reactions, such as K03711, K00384, and K03406, were highly enriched in the reactor when Fe3+ and NO3− were added. The study shows that adding an electron acceptor can enhance interactions between microorganisms, achieve efficient propionate conversion, and improve methane production in the system.

Impact of Oil Sources on In Vitro Fermentation, Microbes, Greenhouse Gas, and Fatty Acid Profile in the Rumen

This study estimated the effects of oil sources on fermentation characteristics, greenhouse gas, microbial diversity, and biohydrogenation of fatty acids in the rumen. In vitro ruminal incubation was performed with 7 mg of oil source, 15 mL rumen buffer, and 150 mg of synthetic diet at 39 °C for 0, 3, 6, 12, and 24 h. Oil sources consisted of corn oil (CO; linoleic acid (C18:2n-6)), linseed oil (LSO; linolenic acid (C18:3n-3)), or Ca-salts (protected C18:2n-6). The ruminal gas was collected for CH4 and CO2 analysis. Incubated rumen buffer was sub-sampled for the analysis of microbial quantification, fermentation characteristics, and fatty acid profiles. The results showed that Ca-salt increased acetate (p = 0.013), while CO increased propionate (p = 0.007). Fibrobacter succinogenes, Ruminococcus flavefaciens, and R. albus increased (p < 0.05) with Ca-salt after 12 h of incubation, while Streptococcus bovis increased (p < 0.05) by LSO. The CO and Ca-salt resulted in the highest C18:2n-6 (p = 0.002), while LSO resulted in the highest C18:3n-3 (p = 0.001). The Ca-salt had the lowest C18:0 (p = 0.002), but the highest C18:1cis-9 (p = 0.004). In conclusion, Ca-salt supplementation resisted biohydrogenation to some extent, decreased methanogenic archaea and protozoa, and exerted less toxic effects on fibrolytic bacteria.

Aspergillus spp. isolated from the bovine gastrointestinal tract improve organic acid profiles in Urochloa decumbens fermentation

During the dry season, high productivity of cattle cannot be sustained through the supply of tropical forage alone, and microbial additives or probiotics represent potential alternatives to improve the performance of animals raised on pastures. In the present study, we evaluated organic acid profiles following the in vitro fermentation of Urochloa decumbens mediated by Aspergillus spp. isolated from the bovine digestive tract. Twenty fungal isolates were evaluated after 96 and 144 h of fermentation of U. decumbens hay (UDH) in saline solution, Sabouraud dextrose broth, or ruminal fluid. Following fermentation, organic acids in the culture media were detected using high-performance liquid chromatography. The production of major fermentation acids differed across fermentation times, fungal isolates, and culture media. Using UDH in saline solution as the sole substrate, gluconic acid was the major fermentation product of fungal isolates. Fermentation of UDH in Sabouraud dextrose broth produced butyric, citric, and propionic acids. Fermentation of UDH in ruminal fluid produced acetic, propionic, and butyric acids, with significant and positive correlations among their production. Five selected isolates increased propionate proportion relative to the control, indicating potential as additives or probiotics for ruminants receiving fiber-rich diets.

Optimizing volatile fatty acid production from municipal sludge: Linking microbial activity with reactor performance

Literature on optimum levels and combinations of bioreactor operating parameters to maximize volatile fatty acids (VFAs) via anaerobic digestion (AD) is still scant and contradictory. This study investigated the interactive impact of digester sludge retention time (SRT), temperature, and pH on optimizing VFAs production and linking reactor performance to acidogenic activities. VFAs production from municipal sludge was maximized in semi-continuous flow acid fermenters (AFs). Batch fermentation tests were utilized for the specific acidogenesis activity assays (SAdA) with a simpler substrate (glucose and acetic acid) and inocula from AFs. Fermenters operated at high pH of 8, low SRT of 2 days, and varying temperatures of 55 and 45 °C had the highest chemical oxygen demand (COD) solubilization and acidification yields. Similar fermenters had the highest VFAs fold increase (1.7–2.2) over the substrate, largest acetic acid contribution to total VFAs (52–58%), and maximum SAdA extent (368–461 mL H2/g VSS inoculum). Maximum hydrogen production rate indirectly represented substrate utilization rate, growth of the acidogens, and hence the specific activities of the acidogenic bacteria in the AFs. These results suggested that batch acidogenic assays could provide quantitative information regarding the presence and activities of cultures in continuously-fed AD utilizing more complex substrates, e.g. municipal sludge. A multiple linear regression model was derived successfully predicting VFAs fold increase of AFs with an R-squared value of 0.9999. The constructed contour plots predicted higher VFAs at relatively high fermenter pH (7.5–8.0), lower SRT (2–2.2 days), and lower temperatures (45–48 °C).

Insights into the role of biochar on the acidogenic process and microbial pathways in a granular sulfate-reducing up-flow sludge bed reactor

In this study, the effect of biochar on sulfate reduction and anaerobic acidogenic process was explored in a granular sulfate-reducing up-flow sludge bed reactor in both long-term operation and batch tests. Both bioreactors had a high sulfate reduction efficiency of over 95% during the long-term operation, while the reactor with biochar addition showed higher sulfate reduction efficiency and stronger robustness against volatile fatty acids accumulation with a higher organic loading and sulfate loading rate. Batch tests showed that adding biochar significantly lessened the lag phase of the sulfate-reducing process, accelerated the adaption of acidogens, and facilitated both production and utilization of volatile fatty acids. The microbial pathways proved that biochar could regulate the acidification fermentation pathway and facilitate the enrichment of assimilative desulfurization bacteria. Overall, this study revealed that the acidogenic sulfate-reducing metabolic pathway could be enhanced by biochar, offering a potential application for effective sulfate-laden wastewater treatment.

Fermentation in Pineapple Juice Significantly Enhances Ornithine and Citrulline Production in Lactococcus lactis MSC-3G Isolated from Sugarcane.

Lactic acid bacterial (LAB) fermentation of functional amino acids using fruit juices as a cultivation medium is not well-documented. In the present study, we successfully isolated a high ornithine- and citrulline-producing Lactococcus lactis strain, designated MSC-3G, from sugarcane and investigated the ornithine and citrulline production profile using various fruit juices as a cultivation medium. Among fruit juices, pineapple juice exhibited the highest potentiality to initiate ornithine production (56 mM), while the highest citrulline yield was obtained during lime juice cultivation (34.5 mM). Under the optimal cultivation condition, the highest yield of ornithine and citrulline in pineapple juice reached 98.9 ± 2.2 mM and 211.1 ± 35.7 mM, respectively, both of which were significantly higher than that in the well-known industrial strain of Corynebacterium (C.) glutamicum. Additionally, citrulline production was dependent on oxygen supplementation and increased twofold when grown aerobically. Whole genome sequencing showed that the MSC-3G genome possesses the arginine deiminase (ADI) gene cluster arcABD1C1C2TD2. The results of the ADI pathway enzyme activities of MSC-3G showed a significant increase in arginine deiminase activity, while ornithine carbamoyl transferase activity was decreased, which in turn indicates the high citrulline-accumulation ability of MSC-3G when cultivated in pineapple juice.

Comparison of Rhizopus Sp. and Lactobacillus Spp. Performance in Lactic Acid Fermentation of Sugar Palm (Arenga pinnata) Solid Waste

Lactic acid is an important component of the manufacturing polylactic acid (PLA), which can produce by using high-lignocellulosic biomass (such as rice husk), The sugar palm (Arenga pinnata) industry produces an abundant amount of lignocellulosic solid waste. The poor utilization of sugar palm solid waste (SPSW) leads to its potential as a fermentation medium due to its reducing sugar content. Lactic acid fermentation is often conducted using lactic acid bacteria (LAB). However, filamentous fungi such as Rhizopus sp. also have the potential to produce lactic acid in fermentation. In the study, SPSW was pretreated using the acid-organosolv method. First, it was ground and screened up to 100-120 mesh. The output sample of the screener was pretreated chemically using dilute acid (H2SO4) with a solid-to-liquid ratio of 1:5 w/w for 40 minutes at 120°C and organosolv (ethanol 30%) with a solid: liquid ratio of 1:7 w/w for 33 minutes in 107°C. Enzymatic hydrolysis was performed using the cellulase enzyme. The fermentation was conducted using microorganisms of Rhizopus sp. (R. oryzae and R. arrhizus) and Lactobacillus spp. (L. casei and L. rhamnosus) at various fermentation temperatures. The fermentation results were analyzed, with the results showing that the lactic acid concentration produced using Lactobacillus sp. was higher (4.396 g/L for L. casei and 4.089 g/L L. rhamnosus) than that using Rhizopussp. (2.248 g/L for R. oryzae and 2.742g/L for R. arrhizus).

Engineering the Lipid and Fatty Acid Metabolism in Yarrowia lipolytica for Sustainable Production of High Oleic Oils

Oleic acid is widely applied in the chemical, material, nutritional, and pharmaceutical industries. However, the current production of oleic acid via high oleic plant oils is limited by the long growth cycle and climatic constraints. Moreover, the global demand for high oleic plant oils, especially the palm oil, has emerged as the driver of tropical deforestation causing tropical rainforest destruction, climate change, and biodiversity loss. In the present study, an alternative and sustainable strategy for high oleic oil production was established by reprogramming the metabolism of the oleaginous yeast Yarrowia lipolytica using a two-layer "push-pull-block" strategy. Specifically, the fatty acid synthesis pathway was first engineered to increase oleic acid proportion by altering the fatty acid profiles. Then, the content of storage oils containing oleic acid was boosted by engineering the synthesis and degradation pathways of triacylglycerides. The strain resulting from this two-layer engineering strategy produced the highest titer of high oleic microbial oil reaching 56 g/L with 84% oleic acid in fed-batch fermentation, representing a remarkable improvement of a 110-fold oil titer and 2.24-fold oleic acid proportion compared with the starting strain. This alternative and sustainable method for high oleic oil production shows the potential of substitute planting.

Estimation of the repair efficiency of collagen matrices on the model of thermal burn

Background. In the world, dozens of new local wound healing agents are developed and improved every year, which undergo preliminary tests on laboratory animals due to the presence of common phases of the course of the wound process with humans.The aim of the study was to evaluate the wound healing effect of matrices obtained on the basis of the recycling of collagen-containing waste.Materials and methods. Collagen matrices are obtained from substandard leather raw materials subjected to treatment with fermented milk composition (KM1) and lactic acid (KM2). The wound healing effect was studied on the model of thermal burns on Wistar rats in 5 groups: 1st – control (natural wound healing); 2nd – experimental 1 (processing KM1); 3rd – experimental 2 (processing KM2); 4th – experimental 3, comparison group (“Levomekol”) and 5th – intact animals (normal, without burns). Wound healing was assessed by the results of planimetry on days 1, 3, 5, 7, 9, and 13 and by histological analysis of the skin tissue on days 6, 13, and 20. On days 6 and 13, the summary antioxidant activity, the total content of leukocytes, erythrocytes, the activity of the catalase enzyme, and the content of malondialdehyde were determined in the blood of rats.Results. With thermal damage to the skin, an IIIA degree burn was formed, accompanied by the development of dry coagulation necrosis. The use of collagen matrices restored the total content of leukocytes, reduced the area of the burn wound, normalized the content of malondialdehyde, the total antioxidant activity and the activity of catalase in the blood. Histomorphometric studies have confirmed the dynamics of skin tissue recovery after a burn. The effectiveness of the use of matrices was comparable to the pharmacopoeial drug “Levomekol”. A higher wound healing effect was noted when using the KM1 matrix.Conclusion. On the model of thermal burn, the wound-healing effect of collagen matrices was established, as evidenced by the results of restoring the number of leukocytes, reducing the area of the burn wound and restoring the histostructure of the skin. One of the molecular and cellular mechanisms of wound healing is the inhibition of lipid peroxidation reactions and the restoration of the antioxidant potential of the body.

Effects of ensiling conditions on pyrrolizidine alkaloid degradation in silages mixed with two different Senecio spp.

ABSTRACT Pyrrolizidine alkaloid (PA) producing plants like Senecio jacobaea or Senecio vernalis are undesirable in fields for forage production, since PA are toxic to animals and humans. Previous studies have shown that ensiling can decrease the PA content in forages; however, no direct comparison of diverse PA from different Senecio spp. under various ensiling conditions has been made. Therefore, it was hypothesised that individual PA might react differently to ensiling, and silage inoculation with Lactobacillus will affect PA degradation because of a quick drop in pH, contrastingly to poor silage qualities resulting from contamination with soil. Laboratory scale grass silages were prepared in a multifactorial design with two levels of dry matter contents, four ensiling treatments and two storage durations (10 and 90 d). For each combination, four replicates were prepared individually. Ensiling treatments were (1) 10 ml water per kg fresh matter as control (CON), (2) 10 ml heterofermentative Lactobacillus buchneri strain LN4637 at 3 · 105 cfu/kg fresh matter plus 25 g molasses/kg fresh matter (LBHE), (3) 10 ml homofermentative lactobacilli at 3 · 105 cfu/kg fresh matter plus 25 g molasses/kg fresh matter (LBHO) and (4) 10 g soil/kg fresh matter (SOIL). Treatments affected formation of fermentation acids. Acetic acid was highest with treatment LBHE, and butyric acid was highest with treatment SOIL. All ensiling treatments effectively reduced total PA content by degrading the PA N-oxide (PANO) fraction. In parallel, though, the fraction of the tertiary base forms increased by around one-tenth of the original PANO content. Contents of jaconine and senkirkine were higher after ensiling than before, with regards to the sum of PA and PANO for jaconine, indicating higher stability or new formation through degradation of other PA. Overall, ensiling offers opportunities to decrease the PA-PANO content in feed and therefore lowers the risk of intoxication by Senecio in livestock.

​Optimization of Fermentation Factors for Vinegar Preparation from Sugarcane Jaggery using Response Surface Methodology

Background: Vinegar, an acidic functional fermentation product and known for its diverse health benefits was developed using liquid jaggery. A study was conducted to standardize the method of vinegar production from liquid jaggery using two different sugarcane varieties viz., CoH160 and Co89003. Methods: The submerged fermentation of liquid jaggery was carried out using yeast Saccharomyces cerevisiae and vinegar was produced using Acetobacter aceti. For the computation analysis of an optimized solution, a central composite rotatable design was applied which constituted three variables temperature (°C), inoculum concentration (%) and incubation time (days) and its influence on acetic acid percent as an important response was studied using Response Surface Methodology. Overall, twenty experimental trials were conducted as well as assessed on the vinegar quality indexes. Result: Vinegar prepared with 7.5 per cent inoculum concentration, incubated for a fermentation period of 12.5 days at 28.5°C was selected due to maximum acetic acid concentration achieved ( greater than 3.5% (w/v). The optimized vinegar contained total soluble solids (4.55-4.75 °Brix), reducing sugar (0.26-0.29%), total sugars (2.7-2.8%), titratable acidity (4.72-5.10%), pH (4.28-4.52), ascorbic acid (17.64-19.97%), alcohol content (0.68-0.79%), acetic acid (3.52-3.83%) and total phenols (36.69-38.22 mg/100 ml). The liquid jaggery vinegar had a bright yellow- brown color, cane flavor and vinegar aroma. It was found organoleptically acceptable.

Protein Recovery and Quality of Alfalfa Extracts Obtained by Acid Precipitation and Fermentation

Protein Recovery and Quality of Alfalfa Extracts Obtained by Acid Precipitation and Fermentation

Higher total faecal short-chain fatty acid concentrations correlate with increasing proportions of butyrate and decreasing proportions of branched-chain fatty acids across multiple human studies.

Metabolites produced by microbial fermentation in the human intestine, especially short-chain fatty acids (SCFAs), are known to play important roles in colonic and systemic health. Our aim here was to advance our understanding of how and why their concentrations and proportions vary between individuals. We have analysed faecal concentrations of microbial fermentation acids from 10 human volunteer studies, involving 163 subjects, conducted at the Rowett Institute, Aberdeen, UK over a 7-year period. In baseline samples, the % butyrate was significantly higher, whilst % iso-butyrate and % iso-valerate were significantly lower, with increasing total SCFA concentration. The decreasing proportions of iso-butyrate and iso-valerate, derived from amino acid fermentation, suggest that fibre intake was mainly responsible for increased SCFA concentrations. We propose that the increase in % butyrate among faecal SCFA is largely driven by a decrease in colonic pH resulting from higher SCFA concentrations. Consistent with this, both total SCFA and % butyrate increased significantly with decreasing pH across five studies for which faecal pH measurements were available. Colonic pH influences butyrate production through altering the stoichiometry of butyrate formation by butyrate-producing species, resulting in increased acetate uptake and butyrate formation, and facilitating increased relative abundance of butyrate-producing species (notably Roseburia and Eubacterium rectale).

Microbial lactate utilisation and the stability of the gut microbiome.

The human large intestinal microbiota thrives on dietary carbohydrates that are converted to a range of fermentation products. Short-chain fatty acids (acetate, propionate and butyrate) are the dominant fermentation acids that accumulate to high concentrations in the colon and they have health-promoting effects on the host. Although many gut microbes can also produce lactate, it usually does not accumulate in the healthy gut lumen. This appears largely to be due to the presence of a relatively small number of gut microbes that can utilise lactate and convert it to propionate, butyrate or acetate. There is increasing evidence that these microbes play important roles in maintaining a healthy gut environment. In this review, we will provide an overview of the different microbes involved in lactate metabolism within the gut microbiota, including biochemical pathways utilised and their underlying energetics, as well as regulation of the corresponding genes. We will further discuss the potential consequences of perturbation of the microbiota leading to lactate accumulation in the gut and associated disease states and how lactate-utilising bacteria may be employed to treat such diseases.

Optimizing bio-ethanol production from cabbage and onion peels waste using yeast (Saccharomyces cerevisiae) as fermenting agent

Production of bio-ethanol from lingocellulosic materials is providing a long-term sustainable for fuel supply. Cabbage and onion peels waste is one of cheap source of lignocellosic materials to serve as feedstock for bio-ethanol production. With the objective of evaluating its potential for bio-ethanol production, different concentrations (50g, and 100g) of Cabbage and onion peels waste treated with 1% diluted sulfuric acid and untreated were subjected to batch fermentation for 12 days with 0.5% and 1% yeast inoculums. Percent of bio-ethanol production, cell density and reducing sugars were measured at an interval of 4 days starting from the beginning. Results of these study showed that ethanol production was observed starting from the 4th day of fermentation, but its amount peaked 26.51 from 100g substrate with 1% inoculum on the 8th day of fermentation, and declined on 12th days (21.06%) from the same substrate concentration. Pretreated substrate showed significantly higher ethanol production than untreated. In agreement with ethanol production, cell density and reduction in reducing sugar were observed in the same pattern. Compared ethanol production between untreated substrates yield of 20.96%, and treated substrates yielded of 26.51%. Overall, this study showed that acid pre-treatment, inoculum concentration, fermentation period and substrate concentration affect the amount of bio-ethanol production. Finally, it can be concluded that the production of bioethanol from Cabbage and onion peels waste is economically and environmentally viable. Extensive use of these Wastes for bioethanol production may have twofold advantages, viz. reduction of its negative impact on environmental hygiene and generation of bio-ethanol.

Meta-fermentation system with a mixed culture for the production of optically pure l-lactic acid can be reconstructed using the minimum isolates with a simplified pH control strategy.

Meta-l-lactic acid fermentation from non-treated kitchen refuse was reconstructed using a combination of isolated bacterial strains under several pH control strategies. The meta-fermentation system was successfully reconstructed using a combination of Weizmannia coagulans MN-07, Caldibacillus thermoamylovorans OM55-6, and Caldibacillus hisashii N-11 strains. Additionally, a simplified constant pH control strategy was employed, which decreased fermentation time and increased production. The optimum pH (6.5) for the reconstructed meta-fermentation was favorable for the respective pure cultures of the three selected strains. The l-lactic acid production performance of the reconstructed meta-fermentation system was as follows: concentration, 24.5g L-1 ; optical purity, 100%; productivity, 0.341g L-1 h-1 ; yield, 1.06g g-1 . These results indicated that constant pH control was effective in the reconstructed meta-fermentation with the best performance of l-lactic acid production at pH optimal for the selected bacterial growth, while the switching from swing pH control would suppress the activities of unfavorable bacterial species in un-isolated meta-fermentation.