Modeling inhibitory activity of a novel antimicrobial peptide AMPNT-6 from Bacillus subtilis against Vibrio parahaemolyticus in shrimp under various environmental conditions

Vibrio parahaemolyticus is recognized as the leading cause of human gastroenteritis associated with the consumption of seafood. NT-6 antimicrobial peptide (AMPNT-6) that is a novel antimicrobial peptide secreted by Bacillus subtilis NT-6 isolated from Natto which is a Chinese traditional fermented food can be an effective method to reduce V. parahaemolyticus. This study aimed at investigating the factors that affected the application of AMPNT-6, such as temperature, salinity, pH value and sodium pyrosulfite concentration by response surface method and modeled the effect of AMPNT-6 on inhibition to V. parahaemolyticus in shrimp under various environmental conditions. Design-Expert software was chosen to perform regression fit and to establish the antibiotic mathematical model. The results indicated that all the above environmental conditions had no significant interactive effects on the antibacterial activity of AMPNT-6. The quadratic polynomial mathematical model was established and obtained the quadratic regression equation of the predictive value Y (bacterial colony number) and variables x1 (temperature), x2 (sodium chloride concentration), x3 (pH), x4 (sodium pyrosulfite concentration) and x5 (AMPNT-6 concentration) in a certain range: Y = 6.60 + 0.34x1 − 0.23x3 − 0.19x5 − 0.29x12 + 0.19x22 + 0.3x42 − 0.35x1x2 (R2 = 0.8963). The experimental values were shown to be in good agreement with predicted values. The established model had a high fitting degree and could predict the inhibition effect of AMPNT-6 toward V. parahaemolyticus growth in shrimp under various conditions.