Optimization of the Antibacterial Activity of Half-Fin Anchovy (Setipinna taty) Hydrolysates

In some cases, food proteins hydrolyzed by protease can release antibacterial peptides. In this study, antibacterial activities of half-fin anchovy (Setipinna taty), digested by papain, pepsin, trypsin, alkaline protease, acidic protease, and flavoring protease, were measured, respectively. Additionally, the mechanism of antibacterial action was investigated. Results showed that half-fin anchovy pepsin hydrolysate displayed higher antibacterial activity than other hydrolysates. Response surface methodology was then used to optimize pepsin hydrolysis parameters using a central composite design method. The results demonstrated that pepsin-to-substrate level of 1,100 U/g, pH of 2.0, reaction time of 2.4 h, and water-to-substrate ratio of 4:1 (v/w) were the optimal conditions to generate antibacterial hydrolysate. The optimized half-fin anchovy pepsin hydrolysate (HAHp) effectively inhibited the growth of Escherichia coli CGMCC 1.1100, Pseudomonas fluorescens CICC 20225, Proteus vulgaris CICC 20049, and Bacillus megaterium CICC 10324 with the minimal inhibitory concentration values ranging from 28.38 to 56.75 mu g/ml. The cell integrity of E. coli CGMCC 1.1100 was significantly destroyed after incubation with HAHp for 5 h (p < 0.05), and cell membrane damage was also observed in scanning electron microscopy. It could be concluded that the antibacterial mechanism was partially due to the ability of HAHp to destroy bacterial cell integrity via irreversible cell membrane damage. Moreover, amino acid composition analysis showed that HAHp's nutritional value was superior to the reference used by WHO/FAO, indicating that HAHp could be used as a functional antibacterial agent in food or feed.