Response surface optimization in determining hydrolysis reaction in soybean dregs using the Box Behnken design

Protein hydrolysate from soybean dregs (Glycine max (L.) Merr.) was made through an enzymatic hydrolysis process using a protease enzyme from Bacillus licheniformis. The protein hydrolysis level was evaluated by measuring the hydrolysis degree (DH) value. This research aimed to obtain the best hydrolysis conditions for isolated soybean protein. The condition with the best hydrolysis degree (DH) was optimized using the response surface method (RSM) with Box Behnken Design (BBD) based on three independent variables, namely enzyme concentration, temperature, and hydrolysis time against DH, then checked for model optimization. The optimum condition of enzymatic hydrolysis of soybean dregs protein was obtained by adding 1.2% protease enzyme at 59°C for 2.6 h. The average value of this product's DH with three repetitions was 92.93%, and the yield was 10.39%. The equation describing the variables and correlation of DH is DH = 92.84 + 6.32A-0.4406B-0.5108C, where A, B, and C are E/S concentration, temperature, and time. In optimal conditions, alkaline protease hydrolysis yielded a 1.000 desirability value, with a 95.62%. The hydrolysate soybean protein's three highest amino acid contents are tyrosine 28.98 mg/g, lysine 1.17 mg/g, and methionine 0.36 mg/g. This study describes the possibility of utilizing soybean dregs to produce hydrolysate soybean protein with high yields by enzymatic hydrolysis with protease enzymes from the Bacillus licheniformis bacteria.