Submitted to: Biotechnology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2015
Publication Date: N/A
Interpretive Summary: The breakdown of bovine milk proteins has been shown to release smaller protein fragments which possess biological activities with the potential to impact human health. Specifically, some of these breakdown products have been shown to inhibit the function of an enzyme responsible for high blood pressure in humans. The “food-grade” status of these small proteins suggests they may be used as safe ingredients for controlling high blood pressure. In this study we developed a system for the production of a milk protein fragment with blood pressure lowering activity from lactic acid bacteria commonly used in dairy fermentations. The system allows for the protein fragment to be transported outside of the producing bacteria so that it would be available within a food matrix. The system relies on a “food-grade” molecule, nisin, which regulates the production of the small blood pressure controlling protein within the bacteria. Work is in progress to determine optimal conditions for expression of this small protein in a defined microbiological medium.
Technical Abstract: Peptides with antihypertensive activity have been identified from the enzymatic hydrolysis of bovine milk proteins. A 12-residue peptide (FFVAPFPEVFGK) shown to inhibit the angiotensin I-converting enzyme is released from the enzymatic breakdown of aS1-casein. A synthetic gene encoding this peptide was cloned within the pediocin operon, replacing the nucleic acid sequence encoding the mature pediocin peptide and resulting in a translational fusion between the pediocin leader peptide and the 12-residue hypotensive (C-12) peptide. The recombinant operon was subsequently cloned immediately downstream of the nisA promoter to allow for inducible gene expression with Streptococcus thermophilus ST128, Lactococcus lactis subsp. lactis ML3 and Lactobacillus casei C2. RT-PCR and SDS-PAGE analysis confirmed the expression of the C-12 peptide within the lactic acid bacteria (LAB). The use of a nisin as a “food-grade” inducer molecule and LAB species which are generally regarded as safe (GRAS) suggest that this system could be adapted to allow for in situ overexpression of bioactive peptides within fermented dairy products.