STUDY ON ISOLATION, CHARACTERIZATION AND IDENTIFICATION OF LACTIC ACID BACTERIA DERIVED FROM FERMENTED DAIRY PRODUCTS

Abstract

Lactic acid bacteria (LAB) are important in dairy food fermentation which have beneficial health properties. The research was conducted to isolate, characterize and identify the LAB derived from fermented dairy products like dahi, borhani, matha, lassi, cheese and to assess their antibiotic susceptibility patterns. The bacteria were isolated based on their colony morphology on de Man, Rogosa, and Sharpe (MRS) agar and selected based on gram-staining properties, biochemical properties and molecular tests. Salt tolerance, sugar fermentation and growth at different temperatures and salt concentrations were observed for all isolates. PCR followed by 16S rDNA sequencing was done to identify the bacteria. All isolates survived at low (≤5%) NaCl concentration, but could not tolerate high (≥6%) NaCl concentration. All isolates can ferment glucose, sucrose, and lactose. All the tested isolates were sensitive to antibiotics like gentamicin, ciprofloxacin, tetracycline and ceftriaxone. Finally, the identified bacterial species were Lactobacillus rhamnosus from dahi, lassi and matha samples and Lactobacillus fermentum was identified from the cheese sample which are known as probiotic species. Ultimately, the research revealed two antibiotic-sensitive LAB species suitable for incorporation into fermented dairy product formulations.