The present study is focused on probiotic characterization of four yeasts viz. VIT-SJSN01, VIT-ASN04, VIT-ASN01 and VIT-ASN03 isolated from food samples based on their auto-aggregation, co-aggregation ability and haemolytic activity. All the yeast strains showed good self-adhering and co-adhering potentiality with a value index of greater than 85%. None of the strains exhibited haemolysis which confirmed their non-pathogenic nature. Yeast strains were encapsulated in sodium alginate, sodium alginate coated with chitosan and sodium alginate-gelatinized with starch. Size and morphology of the beads and capsules were determined using SEM analysis. Encapsulation output and viability under storage condition was investigated. It was found that probiotic yeasts encapsulated in sodium alginate beads, chitosan coated beads and microcapsules showed better survival to simulated gastrointestinal conditions compared to free cells.

In the present study, the cultural conditions for exopolysaccharide (EPS) production from probiotic yeast Lipomyces starkeyi VIT-MN03 were optimized using response surface methodology (RSM) to maximize the yield of EPS. Interactions among the various factors viz. sucrose concentration (1-3 g%), NaCl concentration (2-4 g%), pH (3-5), temperature (20-30°C), and incubation period (20-40 days) during EPS production were studied using Box-Behnken design (BBD). The EPS was purified and characterized using various instrumental analyses. The properties like adhesion, antioxidant, biosurfactant, cholesterol removal, and binding ability to mutagens were also tested for EPS produced. Sixfold increase in EPS production (4.87 g L −1) by L. starkeyi VIT-MN03 was noted under optimized condition. EPS showed a high viscosity (1.8 Pa S −1) and good shearthinning properties. Instrumental analysis showed that EPS was heteropolysaccharide composed of glucan, mannan, and rhamnan. Lipomyces starkeyi VIT-MN03 exhibited good self-adhesion (95%) and co-aggregation ability (93%). Adhesion efficiency for yeast inoculum containing 5.5 × 10 7 CFU mL −1 per 9.2 cm 2 of Caco-2 cell (colorectal adenocarcinoma) was noted. The probiotic EPS displayed strong antioxidant ability to scavenge hydroxyl radical and DPPH by 58% and 71% respectively. In addition, biosurfactant activity (86%) and cholesterol removal (90%) ability of probiotic EPS was also tested. EPS bound cells of L. starkeyi VIT-MN03 showed good binding ability to mutagens. These results support the effectiveness of using RSM for maximum EPS production. To the best of our knowledge, this is the first report on optimization of EPS production by probiotic yeast.

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Objective: The objective of this study was to identify the potential yeast isolates at themolecular level and to evaluate their probiotic characteristics.Methods: Molecular characterization was done for five potential probiotic yeast strains. In vitro assays have been conducted to evaluate the probiotic properties such as NaCl tolerance, autoaggregation, and coaggregation. Hemolytic activity, urease activity, and cytotoxicity tests were carried out for safety assay during the characterization of yeast strains. Results:In this study, the yeast strains, viz., LM, MR, GOI, GII2, and WI was identified at the molecular level and named as Yarrowia lipolytica VIT-MN01, Kluyveromyces lactis VIT-MN02, Lipomyces starkeyi VIT-MN03, Saccharomycopsis fibuligera VIT-MN04, Brettanomyces custersianus VIT-MN05, respectively. Maximum autoaggregation (92%) and coaggregation (97 %) were noted in case of L. starkeyi VIT-MN03. All yeast strains showed nonhemolytic activity. In vitro toxicity assay was performed and all the yeast strains showed nontoxic nature. Conclusion:Five yeast strains have been studied for their probiotic characteristics and identified at molecular level. Out of five yeast strains, three strains showed maximum adhesion ability, which is a prerequisite for colonization and protection of gastrointestinal tract. All the yeast strains are validated as a safe bioresources because of their nonhemolytic activities and nonproduction of urease. It can be concluded that the identified yeast strains can serve as promising probiotics in various fields of food industry.