Studies On Preparation And Bioactivity Of Corn Peptides By Microbial Enzyme Method

In the paper, Corn peptides were prepared by hydrolyzing zein with the enzyme from thesolid microbial fermentation. Influence of hydrolysis conditons on peptides bioactivity,preparation and separation of two proteases and examination of active components werestudied, The results provided evidence for developing functional and healthy food.The crude enzymes were prepared by two kinds of methods-ethanol precipitation andammonium sulphate precipitation, which was purified by DEAE-52. The research shows thatthe activity of Bacillus natto alkaline protease was decreased by1.4%and the Asp oryzaeIF-39by0.8%by ethanol precipitation compared with ammonium sulphate precipitation.Because of the complex steps of ammonium sulphate precipitation and needing desalting inthe final step, Ethanol precipitation was choosed to prepare crude enzyme. After the crudeenzyme was seprated by DEAE-52ion exchange column, the purification fold of the Bacillusnatto alkaline protease was89, while Asp oryzae IF-39was109.02. Crude enzyme andseparated components were analysed by SDS-PAGE electrophoresis respectively. Theelectrophoretogram showed that there were more strips in crude enzyme which had complexcomponents, while there was only one single strip in the purified component.The optimal orthogonal experiment results indicated that there was not a positivecorrelation rather than a appropriate hydrolysis degree between hydrolysis degree and theantioxidant activity. At appropriate hydrolysis degree, the antioxidant structures of proteinwere exposed, the antioxidant activity was higer. While DH was higer or lower, theantioxidant structures were not exposed or decomposition. The antioxidant activity was lower.After the gel separation, The antioxidant activity of the component1,2with largermolecular weight and component5with smaller molecular weight was minor. The antioxidantactivity of the component3、4which had moderate molecular weight was higher. it provedthat the relation of DH and antioxidant activity was not direct. Because of the impurity, theantioxidant activity of hydrolyte was lower compared with the component3,4.The determination of zein hydrolyzate ACE inhibitory by HPLC showed componentswhich had moderate molecular weight was higher, and component5which had smaller molecular was higher too.The purity of hydrolysates and antioxidant activity was detected by TLC. The resultsshowed that the hydrolysates contained many components, and the purity of two activecomponents was high after seperation of gel column. After the HPLC, The Chromatogram ofthe active component3、4was correspondence with that of the hydrolysates.