Generation of the antimicrobial peptide caseicin A from casein by hydrolysis with thermolysin enzymes

The generation of the antimicrobial peptide caseicin A (IKHQGLPQE) from a casein substrate using proteolytic enzymes was assessed in silico. This bioinformatic analysis predicted that thermolysin (EC 3.4.24.27) and thermolysin-like enzymes (EC 3.4.24.28) are likely candidates to liberate the bioactive peptide from α_S1-casein. Commercially available sources of the thermolysin enzyme from industrial suppliers were subsequently shown to liberate the 1049 Da caseicin A peptide, under various conditions of hydrolysis, at both lab and pilot scale. The antimicrobial ability of the hydrolysates to reduce pathogen numbers spiked in infant formula trials was subsequently confirmed. For example, numbers of Cronobacter sakazakii were reduced 1000 fold after 3 h of incubation at 37 °C. In conclusion, this study demonstrates the potential to improve the safety of infant milk formula using milk-derived bioactive peptides.