Probiotic Attributes of β-galactosidase Positive Dairy Yeasts

Abstract

Functional foods have attracted consumers due to their therapeutic attributes and the use of probiotics in dairy is also increasing day by day. A number of bacteria are contributing as probiotics so far, but yeasts as probiotic are not well explored. Yeasts remained one of the most important industrial microbes that play different roles in enriching foods including dairy products. Additionally, β-galactosidase (β-Gal) is desirable to decrease the lactose to combat the intolerance in consumers. Therefore, present investigation was carried out for screening of β-Gal activity in probiotic dairy yeasts (Kluyveromyces). Isolates (n=112) of yeasts were obtained from different sources and from different dairy products (i.e. dahi, raw milk, lassi, butter milk, cream, etc.). Amongst, 45 isolates were β-Gal positive and when subjected to PCR based identification were found to be Kluyveromyces spp. The isolates with higher β-Gal activity (n=10) were further tested for probiotic attributes. Isolates screened at different pH (i.e. 1.5, 2.5, 3.5 and 6.5) were tolerant to low pH and also exhibited tolerance to bile salts (0.5, 1.0 and 2.0%). Isolates tested for antibiotic susceptibility showed resistance to gentamycin, penicillin, vancomycin etc., but failed to reveal antimicrobial activity against Salmonella typhi, Listeria monocytogenes, Staphylococcus aureus, Bacillus cereus and Escherichia coli. None of the isolates (n=10) produced gelatinase and DNase. The observations indicate that isolates can be used for the development of yeast based probiotic foods, though it need further in vivo evaluation.