Diversity of Lactic Acid Bacteria in dairy products of Southern Rajasthan

Abstract

Lactic acid bacteria (LAB) are a group of gram positive, non spore forming, cocci or rod shaped, catalase negative and fastidious organisms. They are considered as “GRAS” (Generally Recognized As Safe) organisms. A total of 86 bacterial isolates were isolated from different samples of raw milk, buttermilk and curd by using MRS agar and M17 agar. Lactic Acid Bacteria have similar nutritional and growth requirements, it becomes difficult and laborious to identify them by classical methods. Hence, molecular typing was attempted to find the diversity, 16S rDNA gene amplification was done using specific 16S rDNA primers and amplified gene products were digested with different restriction endonuclease enzymes. Further the 16S rDNA sequencing was carried out and the sequences were compared with the available gene sequences in NCBI website by using BLASTn. All isolates obtained from dairy products were accurately identified as Lc. lactis, Lb. plantarum, Leu. mesenteroides, E. durans, Lb. fermentum, Lc. garviae and Lb. casei. The predominant LAB were Lactobacillus casei and Leu. mesenteroides, which were isolated from all sampling sites. The results demonstrate that traditional fermented dairy products from different regions of Rajasthan have complex compositions of LAB species.