Isolation and identification of gastric acid-tolerant yeast from tapai

Abstract

Lactobacilli and Bifidobacteria are the most extensively employed bacterial strains in marketable probiotic supplements. However, another probiotic was recently developed from yeast screening based on tolerance against gastric acid. This research aimed to isolate yeasts from traditional Indonesian fermented food (tapai). Screening of probiotic yeasts was based on their survival in gastric acid of pH 2.0. Yeast strains were cultured in malt extract agar, and their phenotype and genotype characteristics were identified. Phenotype characteristics were based on yeast cells’ colony, microscopy, and physiology. Meanwhile, genotype characteristics were determined using the PCR-fingerprinting technique to identify the sequence homology compared to the GenBank database and the phylogenetic tree construction. The result showed that SUL and SM isolates have the highest survival on artificial gastric acid of pH 2.0. The SUL isolate from tapai brand “Sumber Madu” has a morphologically wrinkled colony, no pseudo mycelium, white surface colony, and round cell shape. In contrast, the SM isolate from tapai brand “Sari Madu” has a thin wide colony with no pseudo mycelium, turbid white surface, and oval cell shape. After 2 h incubation on gastric acid, SUL and SM isolates grew up to 6.20±0.35 CFU/mL (survival yeast of 82.71%) and 5.75±0.45 CFU/mL (survival yeast of 79.74%), respectively. The SUL isolate was identified as Kodamaea ohmeri, while the SM isolate was identified as Pichia kudriavzevii.