Preparation Of ACEI Peptides From Rice Bran By Integration Of Enzymatic Hydrolysis And Membrane Separation

The problems existing in the present study of obtaining ACEI peptides （a kind of inhibitor for restraining angiotensin I-converting enzyme） from rice bran are that protein conversion rate remains low and enzymes cannot be utilized to their full potential. In order to increase its production, preparation of ACEI peptides by using deffated rice bran was studied by integration of enzymatic hydrolysis and membrane separation.The deffated rice bran components were measured, with protein content 15.8%, fat content 2.3%, moisture content 4.8% and ash content 9.5%. Traditional alkaline method was employed to generate rice bran crude protein with a yield ratio of 25.50% and a purity of 68.85% respectively.Seven different commercial proteolytic enzymes were employed to hydrolyze rice bran crude protein to produce the hydrolysates respectively. And according to their ACE inhibitory activities, three proteolytic enzymes were chosen for further study on optimization of hydrolysis conditions. By single factor experiments and orthogonal experiments, enzyme D was finally selected by comparing their hydrolysates’ACEI activities with three preliminary chosen enzymes under their optimum conditions respectively.Moreover, several membranes with molecular weight cut-offs （MWCFs） of 3～10kDa were used to filter the hydrolysate. The 8kDa MWCF membrane was selected by assessing the IC₅₀ of peptides.With equal quantity of crude material, the relative maximum of conversion was determined by using continuous membrane reactor, which was 68.73%.In the intermittent membrane reactor system, the optimal operation conditions were determined by evaluating the effects of hydrolysis time, substrate concentration, enzyme concentration （[E]/[S]）, hydrolysis temperature, pH, peptides flux on the conversion of rice bran protein. They were: [E]/[S] =10%, hydrolysis temperature=45℃, pH =9.0 and peptides flux= 11mL/min respectively. Correspondingly, the conversion rate of rice bran protein reached 47.50%, which was 1.27 times as much as that by using the batch reactor.Based on the transmembrane pressure of the system and the inhabitation rates in different periods of time, the operation stability of the continuous membrane reactor system was tested. And the results showed that the system could maintain a steady production of rice bran protein for about 210mins. The result also indicated that the productivity （mg protein /mg enzyme） of continuous membrane reactor was 6.37 times higher than that by using the traditional way to obtain ACEI peptides.