Yeast Extract Research Articles

Contribution to the Identification and Study of the Pathogenicity of Bacteria Responsible for Cassava Root Rot in Côte d'Ivoire Production Zones

Background and Objective: Cassava is an important crop for the Ivorian population. However, yields are relatively low. This low productivity is due to cassava root rots, which are sometimes caused by bacteria. The general objective was to identify the main bacterial diseases responsible for cassava tuberous root rot in production areas in Côte d'Ivoire. Specifically, to identify pathogenic bacteria and then to assess the pathogenicity of the bacterial strains isolated. Material and Methods: The plant material consisted of tuberous cassava roots affected by rot. Decay-causing bacteria were isolated on YPGA (Yeast extract Peptone Glucose Agar) culture medium. Strain identification was carried out using the API 20 E and 20NE gallery. Tuberous cassava roots were perforated with a punch and inoculated with bacterial inoculum calibrated to an optical density of 0.2 at a wavelength of 600 nm, corresponding to 108. Results: 174 strains were isolated. The highest proportions of strains were obtained in the localities of Ferké and Man, with 19 and 26% respectively. The bacterial species identified were Roualtella planticola, Serratia liquefaciens, Serratia marcescens, Burkholderia cepacia, Chromobacterium violaceum, Erwinia spp, Enterobacter cloacae, Klebseilla pneumoniae spp ozaenae and Raoutellia ornithinolytica. The Erwinia species was the most frequent in five localities, with proportions of 100 and 71.4% respectively in Agboville and Yamoussoukro. Results showed that 91.5% of bacterial strains tested caused rot (soft or dry). On the other hand, 52.4% of bacterial strains induced dry rot and around 39% induced soft rot. Conclusion: Various bacterial species were identified in this study. In addition, these species vary in their germinative capacity.

Ecuadorian Cacao Mucilage as a Novel Culture Medium Ingredient: Unveiling Its Potential for Microbial Growth and Biotechnological Applications

Cacao mucilage is typically disposed of during processing, yet its abundant content of organic compounds, polysaccharides, and nutrients renders it valuable for various applications. This scientific study investigates the suitability of cacao mucilage as an alternative culture medium for Lactiplantibacillus plantarum, Saccharomyces cerevisiae, and Aspergillus niger, aiming to provide a viable alternative to traditional media. Through a mixed-design approach, the powdered mucilage, peptone, and yeast extract ingredients were optimized using the recovery rates of each micro-organism as the response variable. The optimal formulation of the medium, consisting of 49.6% mucilage, 30% yeast extract, and 20.9% peptone, resulted in remarkable microbial recovery rates. L. plantarum achieved an outstanding recovery rate of 98.18%, while S. cerevisiae and A. niger exhibited recovery rates of 90.57% and 89.90%, respectively. Notably, these recovery rates surpassed those obtained using conventional culture mediums. Thus, cacao mucilage emerges as an effective component for formulating a natural culture medium that facilitates the growth of yeasts, lactic acid bacteria, and fungi. The yeast extract peptone mucilage (YPM) medium demonstrated enhanced growth, particularly for yeasts and lactic acid bacteria, with recovery rates exceeding 90%. Conversely, A. niger displayed a relatively lower recovery rate. These findings emphasize the potential of cacao mucilage as a valuable resource for preparing natural culture media that promotes the growth of yeasts, lactic acid bacteria, and fungi, offering promising prospects for various applications in microbiology and biotechnology.

Enhancing Bioactive Cordycepin Production via Precision Fermentation with an Engineered Aspergillus oryzae

An optimal culture medium and highly stable biometabolites are important in industrial production processes. The response surface methodology with a Box–Behnken design was performed to determine the optimal culture medium of an engineered Aspergillus oryzae strain for cordycepin production by submerged fermentation. The influences of glucose, yeast extract, and adenine concentrations on cordycepin production were explored, and their concentrations were used for experimental design. The results reveal that the optimal culture components involved 30.0 g/L of glucose, 9.8 g/L of yeast extract, and 1.5 g/L of adenine. As predicted, the maximum cordycepin concentration (1724.53 ± 18.30 mg/L) was obtained with a short fermentation time (2 days). A significant increase in cordycepin yield (>50% increase) was observed in the culture grown in the optimized culture medium compared to that grown in the basal medium. A xanthine oxidase inhibitory activity assay demonstrated that the cordycepin product had a pharmacological function. It exhibited strong stability under high thermal and acidic conditions, with over 95% product recovery. The findings of this study are valuable for developing cost-effective processes for producing health-benefiting products.

Optimization of Butanol Production from Mixed Sugars and Sweet Sorghum Bagasse Hydrolysate Using Clostridium beijerinckii TISTR 1461

This study investigated the capability of Clostridium beijerinckii TISTR 1461 to utilize mixed sugars (glucose and xylose) in synthetic media and sweet sorghum bagasse (SSB) hydrolysate for butanol production. Synthetic media containing 60 g/L of glucose and xylose at various ratios were used for butanol production. C. beijerinckii TISTR 1461 preferentially utilized glucose over xylose for butanol production. The highest butanol concentration (PB, 10.25–10.60 g/L), butanol yield (YB/S, 0.27–0.28 g/g), butanol productivity (QB, 0.22 g/L·h), and sugar consumption (SC, 61–63%) were achieved when the glucose content was at least 75% of the total sugars. When an SSB hydrolysate (produced via enzymatic hydrolysis) containing 60.83 g/L of total sugars (glucose:xylose ratio = 88:12, w/w) was used as a substrate for butanol production, the SSB hydrolysate supplemented with 1 g/L of yeast extract and buffers significantly yielded higher PB (15.10 g/L), YB/S (0.31 g/g), QB (0.31 g/L·h), and SC (82%) values compared to the synthetic media. These results indicate that sweet sorghum bagasse hydrolysates containing glucose and xylose mixtures show promise as cost-effective substrates for sustainable butanol fermentation, demonstrating the potential of agricultural residues in biofuel production.

Response surface methodology and repeated-batch fermentation strategies for enhancing lipid production from marine oleaginous Candida parapsilosis Y19 using orange peel waste

Oleaginous yeasts are considered promising sources for lipid production due to their ability to accumulate high levels of lipids under appropriate growth conditions. The current study aimed to isolate and identify oleaginous yeasts having superior ability to accumulate high quantities of lipids; and enhancing lipid production using response surface methodology and repeated-batch fermentation. Results revealed that, twenty marine oleaginous yeasts were isolated, and the most potent lipid producer isolate was Candida parapsilosis Y19 according to qualitative screening test using Nile-red dye. Orange peels was used as substrate where C. parapsilosis Y19 produced 1.14 g/l lipids at 23.0% in batch fermentation. To enhance the lipid production, statistical optimization using Taguchi design through Response surface methodology was carried out. Total lipids were increased to 2.46 g/l and lipid content increased to 30.7% under optimal conditions of: orange peel 75 g/l, peptone 7 g/l, yeast extract 5 g/l, inoculum size 2% (v/v), pH 5 and incubation period 6 d. Furthermore, repeated-batch fermentation of C. parapsilosis Y19 enhanced lipid production where total lipids increased at 4.19 folds (4.78 g/l) compared to batch culture (before optimization). Also, the lipid content was increased at 1.7 folds (39.1%) compared to batch culture (before optimization). Fatty acid profile of the produced lipid using repeated-batch fermentation includes unsaturated fatty acids (USFAs) at 74.8% and saturated fatty acids (SFAs) at 25.1%. Additionally, in repeated-batch fermentation, the major fatty acid was oleic acid at 45.0%; followed by linoleic acid at 26.0%. In conclusion, C. parapsilosis Y19 is considered a promising strain for lipid production. Also, both statistical optimizations using RSM and repeated-batch fermentation are efficient methods for lipid production from C. parapsilosis Y19.

Proteases from an Amazonian Mushroom Species: A Mycotechnological Alternative for the Production of Milk Coagulant.

Edible mushrooms have been used as sustainable sources of proteases of industrial interest. The aim of this research was to investigate the influence of different culture media on mycelial growth and the potential of an Amazonian mushroom species, Auricularia fuscosuccinea DPUA 1624, in the biosynthesis of bovine milk coagulant enzymes. The species was cultivated on Sabouraud agar, malt, glucose, and peptone agar, malt extract agar, and glucose and peptone agar, supplemented with yeast extract for mycelial development. Enzyme biosynthesis was evaluated by submerged fermentation. Subsequently, the cultures were incubated at 28°C for 8days. Proteolytic and coagulant activities were determined using 1% azocasein solution and milk powder as substrates, respectively. In the results of radial growth speed of A. fuscosuccinea, the values were significant in the GYP and SAB + YE culture media. However, GYP agar favored the growth and mycelial vigor of A. fuscosuccinea; therefore, this medium was selected to obtain inoculum in the tests. In submerged fermentation, the MGYP medium favored the synthesis of proteases for A. fuscosuccinea and synthesized coagulant proteases in 100% of the media, in which significant activity was observed in SAB + YE. The significant production of coagulant proteases of A. fuscosuccinea was obtained under the following conditions: inoculum size 10%, 8days of fermentation period, and 8days of inoculum age. The results indicate that A. fuscosuccinea DPUA 1624 has potential for use in industrial manufacturing, especially in dairy products.

Enhancing Dichlorobenzene Degradation in Sulfate-Rich Groundwater Using Yeast Extract: Performance and Microbial Responses

Enhancing Dichlorobenzene Degradation in Sulfate-Rich Groundwater Using Yeast Extract: Performance and Microbial Responses

Spawn-based pellets of Pleurotus ostreatus as an applied approach for the production of laccase in different types of water.

In recent years, oxidoreductase enzymes such as laccases have received considerable attention for their ability to degrade and eliminate organic micropollutants from contaminated water in a process known as enzyme-based wastewater treatment. Thus, methods to produce high laccase activity in water are a point of focus, with white-rot fungi being highlighted as a tool in this context. This study, therefore, explored the applied approach of direct addition of mushroom spawn of the white-rot fungi Pleurotus ostreatus into water and its potential for laccase production under different conditions. Grain spawn was observed to be preferable to sawdust spawn, resulting in laccase activity of 53.9±5.9U/L and 4.8±0.8U/L, respectively. Laccase activity was induced by adding kraft lignin (4g/L), and an eightfold increase to 446.3±43.1U/L was observed for grain spawn. Lignin accumulated in the spawn over time, resulting in brown pellets composed of spawn, mycelium and lignin. Our results demonstrated that high levels of laccase activity could be obtained in different types of water, including effluent municipal wastewater, using this method. No impact from the addition of inorganic nitrogen (ammonium nitrate, N-levels 14mg/L, 140mg/L) or organic nitrogen sources (urea, yeast extract, wheat bran, N-levels 14mg/L, 140mg/L) was observed for the treatment with grain spawn and lignin, suggesting that stable laccase activity can be expected under these nutritional conditions.

Biochemical mechanism underlying the synthesis of PbS nanoparticle and its in-situ photo effect on Shinella zoogloeoides PQ7

Metal sulfide nanoparticles (NPs) with semiconductor potentials are valuable bioremediation end-products that attract great research interests. However, biochemical mechanisms underlying their biosynthesis and photo-effects remain elusive. In this study, we found that biofilm lifestyle remarkably improved lead resistance and PbS-NP biosynthesis in Shinella zoogloeoides PQ7. Surprisingly, biosynthesis of PbS-NP required more than cysteine and H2S production. Transcriptomic and metabolomic analysis indicated that PQ7 responded to lead stress by changing metabolic activities in ABC transporters, oxidative phosphorylation, EPS production, quorum sensing, protein de novo synthesis, flagella assembly and antioxidative reactions, etc. The elevated EPS production and quorum sensing gene expression echoed the favorable roles of biofilm formation in lead resistance. Biosynthesis of PbS-NP required proper oxygen supply, and was impeded by adding kanamycin or using yeast extract as the sole nutrient supply. Investigations on NAD/NADH, ATP, ROS and GSH productions indicated that biosynthesis of PbS-NP was corelated with cellular respiration, energy metabolism, and redox status. Finally, we proved that PbS-NP had the dose-dependent in-situ photo effect on PQ7’s growth and ROS production. This is the first report that pinpoints the role of cellular respiration in PbS-NP biosynthesis, which is essential for further mechanism study and the development of bioremediation techniques.

Enhanced carbon dioxide bio-fixation and protein production of Chlorella pyrenoidosa through a highly efficient sequential heterotrophic and photoautotrophic culture strategy

Chlorella pyrenoidosa is one of the most promising microalgae for protein production with carbon dioxide (CO2) bio-fixation. However, the high production cost and low production capability under traditional photoautotrophic culture mode had severely limited its application. Here, a highly efficient sequential heterotrophic and photoautotrophic cultivation strategy was established. Firstly, the heterotrophic seeds culture conditions were optimized with glucose as the carbon source and 1 g L−1 of yeast extract was selected as a useful stimulus to boost cell growth. Then, the heterotrophic cells were transferred to photoautotrophic conditions directly and cultured under varied concentrations of CO2. Moreover, 8 % (v/v) of CO2, high light and high initial cell density were found to be beneficial for cell growth and CO2 sequestration. Finally, different initial nitrogen concentrations and nitrogen feeding strategies were evaluated to increase the protein content to 62.69 % of dry biomass. These results provide feasible strategies for efficient CO2 sequestration and protein production jointly in C. pyrenoidosa.

Utilization of Hydrolysis of Protein Concentrates Prepared From the Waste of Common Carp Fish using Trypsin Enzyme for the Growth of Lactic Acid Bacteria

This study aimed to use trypsin enzyme hydrolysates of protein concentrates prepared from the waste of common carp fish (Cyprinus carpio) for the growth of lactic acid bacteria. Trypsin enzyme has been used in the hydrolysis of acid and base protein concentrates for various times, including 60, 120, and 180 minutes. The solubility and emulsification property of the produced hydrolysates was studied. The EAI and ESI at pH 2 and 12 gave the highest values for solubility, , while the lowest values at pH 4. Hydrolysates were used to prepare culture media as an alternative to the MRS medium. Peptospecial and Beef extract were replaced in the commercial media with hydrolysates, and two types of culture media were prepared, one containing yeast extract and the other without it. The enzymatic reaction time had a significant effect on the number of Lactobacillus acidophilus and Bifidobacterium animalis colonies, and yeast extract had a significant effect on the number of colonies of Lactobacillus rhamnosus GG. In contrast, the enzymatic reaction time had not affected the number of colonies of Lactobacillus plantarum and Bifidobacterium infantis. This study is recommended to study the response of other types of lactic acid bacteria and the suitability of the culture media prepared in this study to their growth requirements.

Optimizing malathion biodegradation by Bacillus cereus via a design of experiment framework

Bacteria have effectively been employed to biodegrade pesticides, and current research was envisioned to investigate malathion degradation by Bacillus sp. isolated from field soils. About 30.87–72.25% biodegradation was observed after 96 h with the Bacillus sp. when malathion was used as sole carbon, which increased to 45.77–100% after 240 h at initial malathion concentrations of 0.005–0.1%, respectively. The influence of co-substrates, pH, pesticide concentration, rpm, temperature, and inoculum doses were examined to further optimize malathion biodegradation, and the effect of these factors was investigated by the Taguchi design of experiments (DOE). The optimal biodegradation conditions were obtained at 0.1% (w/v), glucose and yeast extract, pH − 7, temperature − 40 °C, malathion concentration − 0.03% (v/v), agitation − 150 rpm, and inoculum dose − 2% (v/v). The biodegradation rate was boosted to 98% at optimal conditions within 36 h. Malathion degradation was confirmed by ultra-high performance liquid chromatography (UHPLC) studies, followed by the elucidation of three different biodegradation/transformation pathways through GC/MS analysis. Biodegradation analysis of malathion by GC/MS confirmed the formation of a monocarboxylic acid, malaoxon, mercaptosuccinic acid, and phosphorus moiety. These findings unequivocally corroborate that Bacillus sp. inherits immense potential for biodegrading malathion at a wide range of environmental conditions and provides a workable solution for bioremediation of malathion.

Influence of the elicitors on the accumulation of secondary metabolites and antioxidant activities in the <em>Polyscias fruticosa </em>(L.) Harms <em>in vitro</em> roots

Polyscias fruticosa (L.) Harms, belonging to the Ginseng family (Araliaceae), is a valuable medicinal plant in Vietnam. Recognized in the Vietnamese Pharmacopoeia, it is esteemed for its antioxidant, anti-inflammatory, and antipyretic properties, making it a significant contributor to traditional medicine. This research contributes to the understanding of elicitor-induced changes in antioxidant activity, and secondary metabolite content of in vitro root extract of P. fruticosa. The results showed that the antioxidant activity of the root extract tested by DPPH radical scavenging assay with an IC50 value of 1.28 mg/mL in the baseline and the lowest IC50 value of 0.89 mg/mL in the medium treated with yeast extract (YE). The highest total phenolic and flavonoid content were displayed in jasmonic acid-treated samples at 24.31 ± 2.86 mg gallic acid/g extract and 29.25 ± 0.26 mg quercetin/g extract, respectively. The highest saponin was also produced in roots elicited by jasmonic acid, where it reached about 167.19 ± 3.29 mg aescin/g extract. Furthermore, investigation with antioxidant enzyme activities showed another superiority when using elicitors YE (64.4 ± 3,14 U/mg protein) and mannitol (Man) (65.39 ± 3.85 U/mg protein) in peroxidase (POD) activity and using jasmonic acid (8.87 ± 0.74 U/mg) in catalase (CAT) activity. Lastly, TPC and TFC exhibited a positive correlation of r = 0.53 while the TPC and DPPH scavenging activity and TFC and POD showed a remarkably negative correlation of r around -0.8. In conclusion, this study highlights the advancements in eliciting root cultures to enhance specific phytochemicals and antioxidant activity. The information provided holds significant value and will be of interest to scientists engaged in plant biotechnology, particularly in the elicitation of medicinal plant roots.

Culture of Bacillus subtilis and Saccharomyces cerevisiae from byproducts of the enzymatic extraction of Atlantoraja castelnaui oil

The growing trend in global fish consumption has led to the generation of a large amount of waste and byproducts with negative economic and environmental impacts. The production of fish oil from fish processing residues seems to be a sustainable and future opportunity to provide valuable fatty acids for animal and human consumption. In parallel, this alternative valorization of fish waste has increased the demand to explore sustainable extraction methods. Enzymatic hydrolysis is an efficient, rapid and reproducible method for the extraction of oils from fish guts, producing an aqueous phase rich in proteins and soluble compounds. In this work, a highly soluble aqueous phase obtained from the enzymatic extraction of the liver oil of the ray Atlantoraja castelnaui was tested as a source of nutrient for the growth of Bacillus subtilis and Saccharomyces cerevisiae. Culture media were supplemented with the aqueous phase at a final concentration of 10 mg ml-1 total protein. The growth pattern and biomass yield of yeasts cultured in yeast extract peptone-dextrose (YPD) medium did not show statistically significant differences (p: 0.05) with the diluted medium and the aqueous fraction (AF) supplemented medium. Similar results were obtained for B. subtillis and its positive control in Luria Bertani (LB) medium. In both cases, the ability of these inexpensive media to support the growth of microorganisms was demonstrated. Results suggested that the remaining aqueous phase of the discards from A. castelnaui oil production can be used as an alternative substrate for microorganism culture purposes. In this way, a residue destined for disposal could become a product with added value achieving a good result in the context of circular economy.

Cold-active lipase from Psychrobacter alimentarius ILMKVIT and its application in selective enrichment of ω-3 polyunsaturated fatty acids in flax seed oil.

Lipases are one of the ubiquitousenzymes thatbelong tothehydrolases familyand have a wide variety of applications. Cold-active lipases are of major attraction as they can act in lower temperatures and low water conditions because of their inherent greater flexibility. One of the novel applications of lipase is the enrichment of ω-3 polyunsaturated fatty acids (PUFA) in plant and fish oils. This study is aimed at theisolation and identification of cold-active lipase producing bacterium from marine sources, preliminary optimization of medium constituents and conditions, purification of lipase using chromatographic techniques, biochemical characterization, and ultimately theexploration of its application in the enrichment of ω-3 PUFA in flax seed oil. Psychrobacter alimentarius ILMKVIT was identified as the potential cold-active lipase producing bacterium based on its lipolytic activity in rhodamine B agar, titrimetric, and p-nitrophenyl palmitate (p-NPP) assays. One factor at a time (OFAT) analysis, revealed, an incubation time of 4.5days, alkaline pH of9,thetemperature of 25°C, peptone, and yeast extract as nitrogen sources, olive oil as inducer sources, 1% inoculum size, and NaCl as mineral sources as optimum production medium constituents and conditions for lipase production. Lipase purification was achieved by ion exchange and gel-filtration chromatography with a 9.27% yield and 37.51-fold purification. Biochemical characterization reported that the lipase is cold-active, alkaline, enhanced by Fe3+ metal ions, and tolerant to organic solvents, detergents, and inhibitors. P. alimentarius ILMKVIT lipase-hydrolysis followed by urea complexation of flax seed oil resulted in the enrichment of ω-3 PUFA, especially α-linolenic acid (ALA). Hence, the novel cold-active lipase from P. alimentarius ILMKVIT could be used to enrich ω-3 PUFA in flax seed oiland developed further as a prominent nutrient supplement for health benefits.

Gamma-aminobutyric acid fermentation and its fermented extracts on α-glucosidase inhibition and anti-obesity effect.

Levilactobacillus brevis KCL010 was fermented in a simple medium containing 8% (w/v) of rice bran extract. We modified the carbon, nitrogen, and initial pH conditions using 10g/L of sucrose, 10g/L of yeast extract, and 5.0 of pH, respectively. To minimize the pH increase due to decarboxylation, we fermented 100mL of modified synthetic medium containing citrate-phosphate buffer (CPB, pH 5.0) of 25-200mM in 250mL Erlenmeyer flasks. After 72h of fermentation with 50mM CPB, the maximum GABA concentration and conversion efficiency were 3.42g/L and 22.39%. Furthermore, the potential α-glucosidase inhibitory activity, MTT assay, and oil red O staining were determined by fermented extracts of L. brevis KCL010. At the highest concentration of 500μg/mL, the α-glucosidase inhibition percentages for non-fermented rice bran (NFRB), rice bran fermented by L. brevis (RBFL), and GABA (analytical standard) extracts were 55.03%, 58.37%, and 59.48%, respectively. All extracts exceeded 80% viability, suggesting that there was no cytotoxic to 3T3-L1 adipocytes. The rice bran fermented by L. brevis (RBFL) extract shows a high inhibition of lipid accumulation by 29.33% compared to those of extracts.

Efficacy of Hovenia dulcis Fruit Extract in Hangover Mitigation: Double-Blind Randomized Clinical Evaluation.

The fruit of Hovenia dulcis Thunb. (HD) is renowned for its medicinal properties and is rich in bioactive compounds, traditionally used in East Asian medicine as a natural antidote for alcohol intoxication. A randomized, double-blind, crossover, placebo (PLA)-controlled clinical trial was conducted to compare the effects of beverages containing 0.475% HD (HDB), HD combined with 0.1% Pueraria lobata extract (HDPB), and HD combined with 0.02% glutathione yeast extract (HDGB) with the PLA on the symptoms of a hangover. Subjects (n = 30) were randomized into six test groups consuming three beverages, including the PLA. After ingestion, blood alcohol and blood acetaldehyde concentrations were measured at 0, 0.25, 0.5, 1, 2, 4, 6, and 15 h post-alcohol consumption. No significant differences in hematology tests and vital signs were observed amongst the treatment groups; however, at 0.5 and 6 h, the blood alcohol concentrations of the HDB and HDPB groups were significantly lower compared to the PLA group (p < 0.05). Additionally, the blood acetaldehyde concentrations in the HDPB group showed significantly lower values than the PLA after 6 h (p < 0.05). These findings suggest that HD may aid in alcohol detoxification and limit acetaldehyde accumulation. This indicates the potential for HD as a functional food ingredient for alleviating hangover symptoms.

Resistant Rhodococcus for Biodegradation of Diesel Fuel at High Concentration and Low Temperature.

The resistance of 16 Rhodococcus strains to diesel fuel was studied. The minimal inhibitory concentrations of diesel fuel against Rhodococcus were 4.0-64.0 vol. % and 0.5-16.0 vol. % after 7 days of incubation in Luria-Bertani broth and a mineral "Rhodococcus-surfactant" medium, respectively. The three most resistant strains (R. ruber IEGM 231, IEGM 442 and Rhodococcus sp. IEGM 1276) capable of overcoming the toxicity of diesel fuel at a high (8.0 vol. %) concentration and at a low (4 °C) temperature were selected. Respiration activities, growth kinetics, and changes in the diesel fuel composition during the biodegradation process were elucidated using gas chromatography with mass spectrometry, respirometry, and Bradford analysis. Growth conditions were optimised for the improved biodegradation of diesel fuel by Rhodococcus cells using multifactor analysis. They included the simultaneous addition of 1.3 g·L-1 of granular sugar and 0.25 g·L-1 of yeast extract. The twofold stimulation of the biodegradation of individual hydrocarbons in diesel fuel (n-pentadecane, n-hexadecane and n-heptadecane) was demonstrated when glycolipid Rhodococcus-biosurfactants were added at a concentration of 1.4 g·L-1. A total removal of 71-91% of diesel fuel was achieved in this work.

Optimization of bioethanol production using stress-tolerant yeast strains isolated from household alcoholic beverages (Tella, Tej, and Areke) and molasses (as substrate)

Background Yeast strains that are tolerant to several environmental stresses are extensively employed to produce bioethanol from sugar-rich feedstock. Bioethanol production efficiency in Metehara and Fincha Sugar Factories (the two major sugar factories in Ethiopia) is 50% lower than that of similar factories in other parts of the world. Methods In our previous research findings, five wild indigenous strains of multi-stress tolerance yeast were isolated from traditional fermented alcoholic beverages (Tella, Tej, and Areke) in Ethiopia to the purpose of evaluate their potential use for bioethanol using sugarcane molasses as a substrate. Result The optimal parameters for maximum ethanol production were pH of 4.5, 25°Brix, 30°C, 4.0 g/l ammonium sulfate, supplement with yeast extract, and 72 h of incubation period. Under these optimum conditions, 13.13 ± 0.08% (v/v) ethanol was obtained. The yield of hydrous and anhydrous bioethanol from fermented molasses samples were produced at 94.20–95.60% (v/v) and 99.05–99.56% (v/v), respectively. Conclusion According to this finding, Saccharomyces cerevisiae isolate MUT15, Saccharomyces cerevisiae isolate MUT18F, and Saccharomyces cerevisiae isolate R9MU strains have been good candidates for production of industrial bioethanol.

Decolorization of Reactive Dyes by Bacteria Isolated from Textile Dye-Contaminated Soil

Textile dye-contaminated soil samples were collected for the isolation of heterotrophic bacterial population. The isolates were screened primarily for dye decolorization using Luria Bertani broth containing 100 mgL-1 of selected reactive dyes namely Blue FNR (BF), Novacron Navy (NN), or Novacron Deep Cherry (NDC). Secondary screening of dye-decolorizing bacterial isolates was carried out in Bushnell Haas medium. The decolorization efficiency of the isolates was estimated spectrophotometrically. The selected isolates were identified by the analysis of their cultural, biochemical, and molecular characteristics. Among 38 bacterial isolates from the dye-contaminated soil, two bacterial genera Klebsiella pneumoniae strain OS-3 and Bacillus tropicus strain OS-8 were found to have strong ability in selected dye-decolorization. The optimum pH and temperature for dye decolorization in static conditions by both isolates were found to be 6-8 and 37°C within 72 hours, respectively. Efficient dye decolorization was observed under static condition in compared to shaking culture. Both isolates were able to induce decolorization in the presence of co-substrate. Starch, sucrose and glucose as a carbon source and yeast extract as an organic nitrogen source induced the efficiency of Blue FNR, Novacron Navy and NDC dyes decolorization, respectively by both isolates. On the other hand, it was observed that the percentage of dye degradation decreased in the presence of inorganic nitrogen source in the medium. Both isolates retained efficiency to decolorize selected reactive dyes by 70-80% at 5% salinity. The strong decolorizing ability in natural conditions indicates that both bacteria could be used in dye-polluted wastewater treatment. Chittagong Univ. J. B. Sci. Vol. 12 (1 &amp; 2): 91-102, 2024