Production of cysteine-rich antimicrobial peptide by digestion of oyster (Crassostrea gigas) with alcalase and bromelin

A novel cysteine-rich antimicrobial peptide, CgPep33, exhibiting activity against Gram-positive and Gram-negative bacteria and fungi, was isolated from the enzymatic hydrolysates by digestion of oyster with alcalase and bromelin. CgPep33 was purified by using ultrafiltration, ion exchange chromatography on DEAE Sephadex A-25, gel filtration on Sephadex G-25 and high-performance liquid chromatography on a reverse-phase column. CgPep33 inhibited the growth of all studied bacteria (Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus) and fungi (Botrytis cinerea and Penicillium expansum). The IC50 (effective concentration for 50% growth inhibition) values of CgPep33 against all tested bacteria and fungi ranged from 18.6 to 48.2 μg mL−1. Gram-positive bacteria were the most sensitive, with MIC (minimal inhibitory concentrations) values between 40 and 60 μg mL−1. Our results indicate proteolysis strategy opens the road to simple and cheap large-scale production of a safe antimicrobial peptide from marine bivalved molluscs.