ACE Inhibitory Peptides Prepared By Ultrasound Assisted Enzymolysis Of Corn Germ Protein And Integration Of Enzymolysis And Membrane Separation

In order to make full use of the protein resources of corn germ meal,ultrasounic assisted enzymolysis was firstly applied to the preparation of ACE inhibitory peptides from corn germ protein,and then ultrasonic mode,parameters and enzymolysis conditions were optimized.The enzymatic hydrolysates were separated by membrane device to obtain peptides and soluble proteins.Based on integration of enzymolysis and membrane separation with no feeding?IEM-NF?model,integration of enzymolysis and membrane separation with gradient dilution feeding?IEM-GDF?model was performed to prepare ACE inhibitory peptides from soluble proteins.Enzymolysis effect of IEM-GDF model was compared to integration of enzymolysis and membrane separation with continuous feeding?IEM-CF?model.Finally,the prepared ACE inhibitory peptides were subjected to animal experiments to study its antihypertensive effect in vivo and mechanism.The main research contents and conclusions are as follows:?1?Ultrasounic assisted enzymolysis on preparation of ACE inhibitory peptides from corn germ protein.According to protein conversion rate and proportion of highly active peptides,ultrasonic mode was selected as alternating 20/40 kHz dual-frequency concentrating ultrasound.Through the single-factor step-by-step optimization experiment,the ultrasonic parameters were determined as power density of 100 W/L,material concentration of 8%?w/v?,sonication time of 20 min,and ultrasonic temperature was 30°C.After sonication,alkaline protease was added with enzyme dosage of 2000 U/g and enzymolysis time was 2.5 h.Under the optimal conditions,the protein conversion rate was 85.00%,and the highly active peptides accounted for29.63%,whose weight were 300-3000 Da.Compared with the non-ultrasound group and the ultrasonic sink group,protein conversion rate under optimal conditions increased by 16.42%and 8.47%,respectively,and proportion of highly active peptides raised by 13.96%and 10.60%,respectively.This indicated that countercurrent dual-frequency ultrasound-assisted enzymolysis could effectively improve the enzymolysis of corn germ protein.?2?Preparation of ACE inhibitory peptides by IEM-GDF model.3 kDa ultrafiltration membrane was selected and the protein conversion rate was used as an indicator to determine the parameters for IEM-NF model.The results were neutral protease,running time of 50 min,substrate protein concentration of 1.5%,enzyme dosage of 2000 U/g,permeate flux of peptides of 6 m L/min.At this condition,the protein conversion rate was 53.57%.According to the protein conversion rate and transmembrane pressure,the optimum running time of IEM-GDF model was explored.The result showed that maximum operation time was 660 min,and the protein conversion rate was 81.94%.Contrast with IEM-CF model,running time of IEM-GDF model was 1.57 times longer,the protein conversion rate,peptide yield,production efficiency were increased by 74.16%,58.44%,29.14%,respectively,and the IC₅₀ value of peptides was reduced by 11.70%.The results showed that IEM-GDF model had the advantages of long running time,high product yield and product activity.?3?Antihypertension test in SHR of corn germ peptides.Corn germ peptides performed well in maintaining antihypertensive effect for a long period,systolic blood pressure?SBP?of which reached maximal decrease of 18.22 mmHg at 6 h after single intragastric administration.Peptides showed good antihypertensive activity at 9 h,while captopril was rapidly reduced in SBP and duration time was 6 h.In the long-term gavage test,the antihypertensive effect of high-dosed corn germ peptides was significant,which achieved a maximum decrease in SBP of 28.6 mmHg in the second week.Serum biochemical tests showed that the mechanism of corn germ peptides was to reduce ACE activity in kidney,lung and heart of SHR,decrease the content of Renin,ANG II,ET-1 in serum and increase the content of NO and PGI.While reducing blood pressure,corn germ peptides had no side effect to the body and organs.