Optimization of hydrolysis of whey protein concentrate using trypsin-like microbial protease and evaluation of dipeptidyl peptidase inhibitory activity of the obtained hydrolyzed product

Abstract Whey proteins are abundant in peptides that possess various biological activities. In order to enhance the biological properties of protein hydrolysates, it is essential to optimize the conditions of the hydrolysis process as much as possible. Firstly, we have determined the optimal conditions for hydrolysis of whey protein concentrate (WPC) by by filtered trypsin-like protease (FTLP) in vitro conditions. Then, the ability of obtained whey protein hydrolysates against inhibit dipeptidyl peptidase-4 (DiPP4) in vitro conditions was examined. The optimum point for WPC hydrolysis by FTLP with the predicted optimal level of Degree of hydrolysis (DH, 42.9 %) was at an E:S ratio of 5:100 (w/w), 8.6 h, and a temperature of 40 °C. The factual DH under ideal conditions was 42.04 %, indicating the efficiency of the selected model (P ≤ 0.05). The findings indicated that hydrolysates of WPC generated by FTLP, including both the unfractionated section and the fractions obtained via ultrafiltration using 10- and 5-kDa cut-off membranes, exhibited anti-diabetic characteristics. However, the fractions exhibited greater inhibitory effects against the DiPP4 enzyme, with IC50 values of 1.98, 1.19, and 0.9 mg/mL for the unfractionated section, 10-kDa fraction, and 5-kDa fraction, respectively. Moreover, the results indicated that probiotic L. plantarum subsp. plantarumPTCC 1896 or its components may provide opportunities for future management of type-Ⅱ diabetes by inhibiting DiPP4.