Preparation Of Soybean Peptides And Polysaacharides Using Aspergillus Oryzaefermentation Of Soybean Residues

Soybean residues are the main co-products in the processing of soybean products.Soybean residues cannot directly consume due to its high fiber content,containing anti-nutritional factors,like antitrypsin,saponin and hemagglutinin.Soybean residues also contain protein and diet fibre,and it has potential application values in food processing.In this paper,soybean protein and dietary fiber in soybean residues were partially hydrolyzed by proteinase andcellulose,and then hydrolytic soybean residues was fermented by Aspergillus Oryzae.During the fermentation,Aspergillus Oryzae can secreted several kinds of enzymes,like protease,cellulose,amyloase,glucoamylase,which can hydrolyzed protein and insoluble fibreinto peptides and soluble polysaccharides,and other small molecular compounds.The research also focused on selection of enzymes,hydrolysis parameters,fermentation conditions,anddecoloration of fermentation broth.Refining soybean residue by ball mill,40g wet bean dregs with 40 mesh sieve was put in the grinding pot.The rotational speed of the ball mill is constant at 300 r/min.The ratio of ball to material is 10:1.The grinding time is determined to be 4 h.The median particle size of soybean dregs obtained is 462?m.Alcalase alkaline protease and cellulase were usedto hydrolyzeprotein and cellulose in soybean residues.The hydrolysis rates of protein and cellulosewere used to evaluate the degree of hydrolysis.Soybean residues(2.0%,dry basis)was dissolved in pH 7.0 phosphate buffer(0.05 mol/L)containing Alcalase alkaline protease(6.0×10~4 U/g substrate)andcellulase(1.5×10~3 U/g substrate),and then the solution was hydrolyzed 4 h at 50?.The hydrolysate was heated 10min at 80?.The rates of hydrolysis of protein and cellulose were 10.14%and 4.82%respectively.The contents of soluble protein and polysaccharidesin soybean residueswas 1.24%(dry basis)and 3.45%(dry basis)respectively.The content of total soluble solid in soybean residues was 5.28%.Based on the growth characteristics of Aspergillus oryzae(Huniang3.042)in partially hydrolyzed soybean residues.It was demonstrated that the nutrients of partially hydrolyzed soybean residues was suitable to the normal growth of Aspergillus oryzae.Enzymes secreted from Aspergillus oryzae can effectively hydrolyzed soybean proteinand fibre into peptides and polysaccharides.The optimum fermentation conditions of fermented soybean residuesby Aspergillus oryzae were determined.Aspergillus oryzae(10~7/g substrate)was inoculated in 2.0%(dry basis)hydrolysate of soybean residues,and then was cultured 48h at 30?in 130 r/min shake speed.The yield of soluble substance in final fermentation product was 52.8%.Activated carbon was used for decolorization of fermentation broth.Decolorization rate was 76.4%.The final recovery of fermentation product was 96.1%.The main composition of final fermentation products were soybean peptides and soybean polysaccharideswith molecular weight ranging 300~5000 Da and 5000~500000 Da respectively,and it also contained some small molecular substances.The fermentation product was rich in soybean peptides and soybean polysaccharides.It was a kind of good dietary supplement.The characteristics of this processing were lower producing cost,higher utilization efficiency of soybean residues,and nochemical pollution in the processing.It is a kind of environmental-friendly producing technology.