Optimization of Enzymatic Hydrolysis of Channel Catfish Bones for Preparing Antimicrobial Agents

Abstract

The bones of channel catfish (Ictalurus punctatus), a kind of fish processing waste, were hydrolyzed with one of five proteases (alcalase, neutrase, papain, pepsin, and trypsin) in order to generate antibacterial agents. The antibacterial activity of hydrolysates recovered through enzyme hydrolysis was tested by radial diffusion assay (RDA). Pepsin hydrolysate was found to have the greatest antibacterial activity. Thus, the conditions of hydrolysis with pepsin were optimized by response surface methodology (RSM). After screening and optimization, a quadratic model was proposed. The model predicted that the maximum diameter of clear zone, which suggests the optimum antibacterial activity, was around 20.2 mm with a hydrolysis condition of pH 3.5, reaction temperature of 40°C, enzyme-substrate ratio of 1.97/100 (g/g), substrate concentration of 0.15 g/mL, and reaction time of 4 h. Verification experiments under this condition showed a clear zone of 19.8 mm, which agreed well with the model's predicted value. This result indicates that RSM is an effective way to optimize the enzymatic hydrolysis of channel catfish bones to increase antibacterial activity, and the bones of channel catfish are promising resources for generating antibacterial components.

Keywords:

• antibacterial activity
• catfish bone
• enzymatic hydrolysis
• response surface methodology (RSM)
• protease

Acknowledgments

Projects 31071617, 30600420, and 30800255, supported by National Natural Science Foundation of China, contributed to this study. The authors thank Naruhito Aquaculture Company for providing the channel catfish.