The Half Maximal Inhibitory Concentration (IC 50 ) Effect of Protein Hydrolysates from Rainbow Trout ( Oncorhynchus mykiss ) Skin on Enterotoxin A Gene Expression in Staphylococcus aureus

The fish hydrolyzed protein is the potential source of bioactive peptides. These peptides are inactive in the original structure of the protein molecule, but they can be activated after enzymatic hydrolysis. In this research, the effect of the half maximal inhibitory concentration (IC50) rainbow trout hydrolyzed proteins (< 3 kDa) was evaluated on enterotoxin A gene expression of Staphylococcus aureus ATCC 29,213 (the strain of enterotoxin A producer). After affecting IC50 of the fish hydrolyzed protein (< 3 kDa) and S. aureus 1.5 × 108 cfu/ml in BHI broth medium and incubating for the durations 8 and 12 h after exposure (logarithmic phase and stationary phase of S. aureus growth, respectively), the gene expression of enterotoxin A was investigated via Real-Time PCR. gyrA used as a housekeeping endogenous control. Notably only < 3 kDa fish hydrolyzed protein by Flavourzyme enzyme (HF3) showed an inhibitory effect on gene expression of S. aureus enterotoxin A in logarithmic phase. Therefore, fish hydrolyzed proteins can provide a new strategy as natural factors in preventing toxin production, due to the high quality and safety of sensitive foods.