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Fermented foods and beverages are rich source of probiotic microorganisms and yeasts are the most common microorganisms found in these fermented products. Fermented beverages are less explored for probiotics, therefore; the present study was focused on isolation, screening and characterization of probiotic yeast from rice Chhang, a fermented beverage of Lahaul Spiti. Ten yeast isolates were initially isolated from rice Chhang and out of which two isolates Saccharomyces cerevisiae Y196 and Saccharomyces cerevisiae Y197 were selected based on their antimicrobial activity. These two yeast isolates were examined for various probiotic properties such as survival at low pH, bile tolerance, microbial adhesion to hydrocarbons, cholesterol assimilation, exopolysaccharide production and haemolytic activity. Both isolates showed antimicrobial activity against all the tested pathogens used in this study, also showed high acid tolerance at pH 2 and pH 3 and can withstand high bile concentration as compared to control. Percentage of hydrophobicity was found to be 57 % and 41 % in Saccharomyces cerevisiae Y196 and Saccharomyces cerevisiae Y197, respectively. Both isolates were able to show high cholesterol assimilation with a maximum of 90 % in case of Saccharomyces cerevisiae Y197 with taurocholate. They were also found to be positive for exopolysaccharide production and showed no haemolytic activity. Hence, keeping in view the results of present study, these isolates can be proposed for preparation of various probiotic food products. [ABSTRACT FROM AUTHOR]

β-galactosidase also known as lactase (glycoside hydrolase enzyme) has potential uses in the dairy, food, and pharmaceutical industries. Yeast β-galactosidase is an intracellular enzyme which has been isolated from various sources. In this study, different isolates of yeast were assessed for their β-galactosidase productivity, and Kluyveromyces marxianus Y72 resulted in the highest production. β-galactosidase enzyme, which hydrolyses lactose and is largely dependent on its stability under different physical conditions, such as pH, temperature and incubation time. In the present study, the yeast, Kluyveromyces marxianus Y72, was isolated from curd and showed intracellular β-galactosidase activity during the growth phase. To understand further, response surface methodology (RSM) was carried out to optimize the process parameters such as carbon source, nitrogen source, and the growth of Kluyveromyces marxianus Y72 with respect to temperature, pH, and inoculum size. The enzyme activity was maximum (2.65 U/mg dcw) at 30 ˚C, pH 6.0 and at an incubation time of 24 h with galactose (4%) as the carbon source. In conclusion, the current study revealed β-galactosidase from Kluyveromyces marxianusY72 is having significant potential for possible use in various industries. [ABSTRACT FROM AUTHOR]

Response surface methodology (RSM) was used in this study to optimize the fermentation conditions for exopolysaccharides (EPSs) produced by Kluyveromyces marxianus Y72. The results showed that, under the optimal fermentation conditions, K. marxianus Y72 produced mucoid ropy white colonies on ruthenium red skimmed milk agar. Optimal exopolysaccharide production was achieved after 72 h, pH 6.5 and agitation rate 200 rpm with yield of 0.286 ± 0.002 g/L using banana peel extract as a carbohydrate source. The optimal incubation temperature of 25 ˚C showed maximum EPS yield of 0.309±0.005 g/L. Thirty validator runs were carried out using the central composite design (CCD) for the response surface methodology (RSM), which included, carbon concentration, temperature, incubation time, and agitation from one variable at a time (OVAT). EPS was dialysed with 24 kDa membrane for 24 h and the dialyzed EPS was then precipitated with chilled ethanol. By employing the DPPH assay to test the antioxidant activity of crude EPS, 60% activity was achieved, and 74.05% activity was achieved using partially purified EPS at the same concentration of EPS. In crude EPS isolated from K. marxianus Y72, cholesterol adsorption of 64.70% was observed. Antimicrobial activity was also checked against Escherichia coli, Salmonella typhi, Bacillus cereus, Pseudomonas aeruginosa, and Staphylococcus aureus showed negative findings. [ABSTRACT FROM AUTHOR]

The probiotic metabolites called postbiotics synthesized by microorganisms consist of range of molecules namely organic acids, antimicrobial peptides, short-chain fatty acids, exopolysaccharide (EPS), cofactors, vitamins, immune-modulating compounds, enzymes, neurotransmitters etc. LABs are widely recognized as an efficient EPS producer. Hence, the goal of the current study is to statistically maximize the media components for maximum exopolysaccharide production by Lactobacillus plantarum LG138 from primate feces. The de Man, Rogosa and Sharpe (MRS) medium is used for optimization of production process. Batch culture system is used for optimization of exopolysaccharide production in MRS medium using Lactobacillus plantarum LG138. The optimization process of EPS production improved its yield by 2.7-folds (from 12.00 mg/ml to 32.88 mg/ml).The enhanced EPS yield was achieved after optimization of different media components such as sucrose (5%), ammonium sulfate (1.2%), temperature (32.5°C), incubation time (22 h) and pH (6.5) using Response Surface Methodology. The actual experimental value (32.88 mg/ml) was comparable to the predicted maximum EPS production by Lactobacillus plantarum LG138 (32.87mg/ml) under optimal conditions. The in vitro antioxidant assays (free radical scavenging ability and reducing power) revealed antioxidant properties of EPS. These significant activities recommend the possible potential use of EPS in animal food and feed applications. [ABSTRACT FROM AUTHOR]