A new continuous system of enzymatic hydrolysis coupled with membrane separation for isolation of peptides with angiotensin I converting enzyme inhibitory capacity from defatted corn germ protein

In this study, separation of peptides with Angiotensin I converting enzyme (ACE)-inhibitory capacity obtained from ultrasonically pretreated defatted corn germ protein (DCGP) by using a new continuous system of enzymatic hydrolysis coupled with membrane separation (EHC-MS) was investigated. Ultrasonic pretreatment was applied to enhance the enzymatic hydrolysis rate of DCGP, as proved in our previous study. The EHC-MS system was operated in two modes which included the batch system and continuous system with continuous water and substrate feeding and was compared with the EH-offline-MS system. The selection of the membrane was based on the hydrolysate fraction which had the highest activity for inhibition of ACE. The results showed that the 1-3 kDa fraction of DCGP hydrolysates had the lowest IC50 value (0.124 mg mL(-1)) for inhibition of ACE. The degree of conversion (%) of DCGP and output of peptides per unit of the enzyme were significantly (P < 0.05) increased by 55.3% and 55% in the EHC-MS batch process and 79% and 473% in the EHC-MS continuous operation compared to the EH-offline-MS system. The EHC-MS using continuous water and substrate feeding operation was noted to be the best in terms of a high degree of DCG protein conversion (75.68 +/- 1.34) and the output of peptides per unit of the enzyme (78.65 +/- 1.13). The results revealed that the EHC-MS method with constant water and substrate feeding could show a better application in peptide production in the food industry.