Abstract: In order to increase the utilization value of sea cucumber gonads as a potential source of peptides, neutral protease was selected for the hydrolysis of sea cucumber gonads. One-factor-at-a-time method was used to investigate the effects of substrate concentration, enzyme dosage, hydrolysis time, pH and temperature on hydrolysis degree. Following these investigation, a quadratic regression model describing hydrolysis degree as a response to substrate concentration, enzyme dosage and hydrolysis time was set up using a Box-Behnken experimental design. As demonstrated by the results analysis of variance and validation experiments, the model could well indicate the hydrolysis degree of sea cucumber gonads. The optimal hydrolysis conditions of substrate concentration, enzyme dosage and hydrolysis time were determined to be 10.4%, 1154 U/g and 89 min, respectively. Under these conditions, the hydrolysis degree of sea cucumber gonads is 63.12%.

Key words: sea cucumber gonad, protease, response surface analysis, process optimization