Preparation Of Corn Peptide From Corn Gluten Meal By Aspergillus Niger Solid-state Fermentation

Corn yellow powder is also called corn gluten meal (CGM), is the main by-product ofthe production in which the corn starch is producd by wet grinding method. Currently,the most corn gluten meal is used for feed or is abandoned directly. Corn peptide is akind of bioactive peptides which is obtained from the degradation of the corn glutenmeal. Corn peptide is easy to dissolve, has biological activities and a high market value.This topic determined the basic technological process and the optimum processconditions of the preparation of corn peptide which was preparated by solid-statefermentation of corn gluten meal. Furthermore, we separated and purified thefermentation products. Then, we selected the strongest antioxidant components bydetermination of in vitro antioxidant capacity of different components obtained bypurification. At last, we determined the amino acid composition of the products offermentation and purification. We studied the diversification of the amino acidcomposition by contrasting the amino acid compositions after fermentation. The mainresults were shown as follows:1. At first, we screened out the appropriate strains used in solid-state fermentation bydetermining the diversification of Aspergillus niger and Aspergillus oryzae in theprocession of fermentation and the conversion rate of corn peptide. The strains whichare provided with higher protease live and conversion were used in the solid-statefermentation. We discovered that the conversion rate of corn peptide prepared byAspergillus niger is higher than the conversion rate of corn peptide prepared byAspergillus oryzae under the same fermentation conditions. According to theexperimental purposes, we made a choice of Aspergillus niger to use in fermentation.2. Optimizing technics of the fermentation conditions and determing the optimumparameters of preparing soluble corn peptide by Aspergillus niger solid-statefermentation after selecting the appropriate stains used to ferment. Making use of themethods of single factor experiment and orthogonal reperiment to optimize the processparameters. At first, the influence of water content, mixture ratio, initial pH value,fermentation temperature and fermentation time of medium was evaluated. According tothe experimental datas, we found that the influence of water content, initial pH value,fermentation temperature and fermentation time were more obvious than other factors.So we chose water content, initial pH value, fermentation temperature and fermentation time to do orthogonal experiment. The optimal fermentation parameters were definitedon the basis of the datas of orthogonal experiment. The fermentation conditions wereobtained as follow: mixture ratio17:3, water content53%, initial pH value6.0,fermentation temperature33℃, fermentation time90h. Under these experimentconditions, the percent conversion of corn peptide could reach22.151%.3. Corn peptide was obtained by fermentation under the optimal conditions. Thefermentation products obtained were separated and purified into two kinds ofcomponents by gel filtration chromatography. The two kinds of components werenamed component Ⅰ and component Ⅱ. The two components were collectedrespectively and were lyophilized to be powder by freeze-drying. Contrasting the aminoacid compositions of corn gluten meal and fermentation broth, we could discover thatboth of them are basically same. This imagination introduved that the method ofpreparing corn peptide by Aspergillus niger solid-state fermentation can hold theoriginal amino acid pattern of corn gluten.We studied the amino acid compositions of componentⅠand componentⅡ. Then wefound the contents of Glutamate in componentⅠand componentⅡwere lower that infermentation broth, but the contents of Aspartate were higher oppositely. In addition, wediscovered that the amino acid compositions of componentⅠand componentⅡwerebasically same. They both contained mainly with aspartate, threonine, glutamate,proline, alanine, valine and leucine.4. The vitro antioxidant capacity and superoxide scavenging assay of corn peptideobtained by Aspergillus niger solid-state fermentation and componentⅠand componentⅡwere determined. Based on the experimental datas, we originate that antioxidantcapacity of componentⅡwas strongest, and antioxidant capacity of componentⅠwasweakest.