Submitted to: Biotechnology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/29/2007
Publication Date: 11/15/2007
Citation: Renye Jr, J.A., Somkuti, G.A. 2008 Cloning of milk-derived bioactive peptides in streptococcus thermophilus. Biotechnology Letters. 30:723-730. Interpretive Summary: Streptococcus thermophilus is a food-grade bacterium essential for the production of fermented dairy foods including yogurt and cheeses. Its presence in dairy products makes it a good candidate to serve as a host for the expression of novel genes which may increase the functionality and nutritional value of dairy foods. In this study, two new genes were introduced into S. thermophilus. The two genes will allow S. thermophilus to produce two small protein fractions which are normally released from larger milk-proteins during digestion. One of these fractions exhibits antimicrobial activity against a broad spectrum of food-borne pathogens, while the other has been shown to possess antihypertensive activity. S. thermophilus cells containing the new genes were detected by the use of a fluorescent protein which causes the bacterial colonies to glow under UV illumination and were further confirmed by molecular techniques. The expression of these small protein fractions in genetically engineered bacteria will increase their availability and subsequently increase the value of dairy products.
Technical Abstract: It has been shown that the enzymatic breakdown of milk proteins leads to the release of bioactive peptides. Two such peptides are the 11-residue antimicrobial peptide from bovine lactoferrin (BL-11) and the 12-residue antihypertensive peptide from s1-casein (C-12). This report summarizes the cloning of these two bioactive peptides in Streptococcus thermophilus in order to develop bacterial strains that may enhance the functionality and nutritional value of dairy food products. Nucleic acid sequences encoding the peptides were generated by overlapping PCR and were subsequently cloned into a new expression vector under control of the ST2201 promoter. S. thermophilus transformants were successfully identified using GFP as a selectable marker. The presence of the synthetic gene constructs in S. thermophilus was confirmed by PCR techniques.