Author : Garima Bhardwaj and Bhagat Singh

Antimicrobial peptides (AMPs) are small molecular weight proteins with broad spectrum antimicrobial activity against bacteria, viruses, and fungi. There are varieties of antibacterial peptides encrypted within the sequence of milk proteins that are released upon suitable hydrolysis of the precursor protein. AMPs kill microbial cells by interaction with molecules. Present study carried out for optimization of conditions to produce bioactive peptides with antimicrobial activity during fermentation of bovine milk with Lactic Acid Bacteria. We used three different cultures of Lactic Acid Bacteria for the fermentation of bovine milk from different sources. Out of three one was pure culture of Lactobacillus helveticus, second one was curd with unknown culture and third was combination of Lactococcus and Lactobacilli. Culture was inoculated @ 1.0%, 2.0%, 3.0%, 4.0%, and 5.0%, and incubated at 37 degree C, 40 degree C and 44 degree C for a period of 16h, 20h, 24h, and 28h respectively in bovine milk. Bioactive peptides generated during fermentation were separated using different techniques and tested for antimicrobial activity. These peptides first purified with gel filtration technique and then subjected to reverse phase high performance liquid chromatography. Different fractions were collected at different time interval and were subjected to antimicrobial activity against Gram’s positive and Gram’s negative bacterial pathogen. Different peptides showed different antimicrobial effect on the inhibition of pathogen. This study demonstrated that bioactive peptides generated during fermentation with L. helveticus showed a good degree of inhibition including zone of inhibition -17mm against Gram’s negative bacteria and 15mm for Gram’s positive bacteria at 5.1 pH for 20 hours of incubation and combination of Lactococcus and Lactobacilli at 4% inoculation showed a good degree of inhibition zone 15.6 against Gram’s positive bacteria and 12mm for Gram’s negative bacterial when kept at 3.2 pH for 28 hours of incubation.

Keywords: Antimicrobial peptide, bovine milk peptides, fermented milk peptides.