Determining Antimicrobial Activity in Hydrolysates Obtained from Buttermilk Substrates by Trypsin and Pepsin

Milk proteins within their structure and sequence, contain peptides that exhibit antithrombotic, immunomodulatory, antimicrobial, antihypertensive, and other bioactivities. These peptides are released as the enzymes cleave milk proteins at certain locations of the amino acid chains. In this research, four different substrates were hydrolyzed with the gastrointestinal enzymes, pepsin and trypsin. The substrates were buttermilk (BM) and whey buttermilk (WBM), which are waste products of butter and cheese production, and supercritical CO2 fluid (SFE) treated buttermilk (S-BM) and whey buttermilk (S-WBM). SFE acts as a solvent which removes triglycerides from the substrates and changes the overall composition of samples. Resulting hydrolysates were placed on a disk to test on a bacterial lawn. Zones of inhibition were measured to quantify the antimicrobial activity of the peptide solution against specific bacteria. Up to this point in research, only E. coli K12 strain was used for susceptibility test. Some SFE treated hydrolysates showed zone of inhibition which indicated that there were antimicrobial peptides with measurable activities. This research is in its preliminary stage. If buttermilk and whey buttermilk show significant antimicrobial activity, then it would not only appreciate their value, but also be used as natural additives to increase shelf life of various processed foods and as natural antimicrobial agents that can aid in reducing the antibiotic overuse