Preliminary evaluation of probiotic potential of yeasts isolated from bovine milk and curd of Sri Lanka

There has been mounting interest in the health benefits associated with live microorganisms commonly known as probiotics. Many probiotic bacterial species have been identified. However, the potential of yeasts as a source of probiotics has not been well explored. The present study was carried out to screen and identify potential probiotic yeasts from selected dairy sources available in Sri Lanka. Yeasts from raw bovine milk and curd were isolated, purified, selected and phenotypically characterized by performing morphological, physiological and biochemical tests. Isolates were assessed for their ability to survive under simulated gastro-intestinal conditions to explore their probiotic potential. Approximately, 190 colonies similar to yeast were isolated and 45 isolates of the division Ascomycota were selected and coded for convenience (SLDY_001-SLDY_045). Most promising probiotic isolates (20) were genotypically identified to be species of Pichia (55%), Candida (30%), and Kluyveromyces (15%) of the family: Saccharomycetaceae. Considering a threshold of >95% similarity to the type strain, eight different yeast species were identified. Isolates (SLDY_005, SLDY_006 and SLDY_039) of Kluyveromyces marxianus species showed the highest probiotic potential from the pool. The strain confirmation and in-vitro/in-vivo safety assessment of these isolates will further verify their suitability as probiotic starter cultures to be used in local food and pharmaceutical industries