Cloning of milk-derived bioactive peptides in Streptococcus thermophilus.

The enzymatic breakdown of milk proteins releases bioactive peptides. Two such peptides are the 11-residue antimicrobial peptide from bovine lactoferrin (BL-11) and the 12-residue hypotensive peptide from alpha(s1)-casein (C-12). These two peptides have now been cloned in Streptococcus thermophilus to develop strains that 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 ST(2201) 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.