Isolation and characterization of lactic acid bacteria from homemade curd samples of Jammu district

Abstract

Homemade curd is a naturally fermented dairy product that serves as an important habitat for diverse lactic acid bacteria (LAB), many of which are valuable for probiotic and functional food applications. In the present investigation, homemade curd samples were collected from different localities of Jammu district to explore indigenous LAB diversity. A total of 10 samples were processed under aseptic conditions, and serial dilutions were plated on de Man, Rogosa, and Sharpe (MRS) agar for isolation. From these samples, 20 morphologically distinct bacterial colonies were recovered. All isolates were initially characterized by Gram staining and catalase tests, which confirmed that they were Gram-positive, catalase-negative, and non-spore-forming, typical of LAB. Detailed morphological and biochemical analyses were performed, including sugar fermentation patterns, esculin hydrolysis, and citrate utilization. Out of the 20 isolates, seven strains consistently displayed characteristics typical of LAB, with uniform rod-shaped morphology and stable biochemical responses. These seven promising isolates were further subjected to species-level identification using the ABIS bacterial identification system, which classified all of them as members of the genus Lactiplantibacillus, a group widely recognized for its role in fermentation and probiotic functionality. The findings highlight that homemade curd from Jammu is a rich source of indigenous LAB, and the Lactiplantibacillus isolates obtained in this study may serve as potential candidates for starter culture development and probiotic applications after further safety and functional evaluations.