Isolation and selection of probiotic lactic acid bacteria from naturally fermented milk

Abstract

This study aimed to isolate and evaluate probiotic lactic acid bacteria (LAB) strains from naturally fermented cow’s milk in Thai Nguyen. From five collected milk samples, five LAB strains were isolated and had their biological characteristics evaluated. All strains were capable of producing lactic acid under in vitro culture conditions. Among them, strain LAB-TNSC-29 showcased outstanding performance, with high lactic acid production (2.96 mg/100 ml), strong survival under low-pH conditions (3.23 log CFU/ml), and notable probiotic properties, including inhibition of pathogenic bacteria (Escherichia coli, Streptococcus gallinarum,
and Staphylococcus aureus) and co-aggregation with E. coli at 48.35%. Analysis of the 16S rRNA gene sequence (1483 bp) revealed that this strain shared 99.39% sequence similarity with Lactobacillus acidophilus CIP 76.13T. Simultaneously, the phylogenetic tree revealed that strain LAB-TNSC-29 belongs to the genus of Lactobacillus and forms a monophyletic clade with Lactobacillus acidophilus CIP 76.13T. Therefore, LABTNSC-29 was identified as Lactobacillus acidophilus LAB-TNSC-29, holding strong potential for application in the production of probiotic formulations.