Study On The Preparation Of Koji With Soybean Residues And Antioxidants Activity Of Its Extract

Soybean residue, the main by-product of soy products, is not only accounting for 15%~20% in dried soybean, but also rich in protein and physiological active elements. Aspergillus oryzae is a universal strain in traditional fermented industry, which contain complexed enzymes. Using soybean residue as raw material, Koji was produced by fermentation of Aspergillus oryzae. The complex enzymes from aspergillus oryzae were used to hydrolyze Koji, anti-oxidant elements was obtained. In this paper, using soybean residue as a medium, Koji is obtained ,and then hydrolyze the koji to obtain the anti-oxidant elements. The results concluded from experiments were as follows.1. Optimized cultivation conditions for the production of enzyme by Aspergillus oryzae under solid-state fermentation were obtained. The results showed the optimum conditions as followed: at 30℃, wheat bran, bean dregs ratio 1:9, incubation time 48h, inoculum dosage 0.15%, moisture 50%. Under these conditions, the protease activity reached 3283U/g. In addition, Glucose and Ammonium Sulfate can increase the neutral protease activity of the Koji.2. By the Koji autolysis, the extract with antioxidants was obtained. When temperature is 40℃, the solid-liquid ratio is 1:20, the hydrolysis time is 3h, the dissolution rate of protein was 69%. Polypeptides are mostly less than 1000 MW. They were tri-peptides, dipeptides and amino acids. The cellulase and the pectinnase were used to improve the antioxidant components. the dissolution rate of protein was 77.3%, at the dosage of cellulase: 0.3g/L, temperature: 40℃, the solid-liquid ratio of 1:25 for 3h; 0.2ml of the extract can scavenge 49.2% DPPH·free radical, 30μl can scavenge 72.1 % ABTS+, at amount of pectinnase added 1g / L, solid-liquid ratio of Koji to water 1:20, temperature 40℃,for 4h.3. The added cellulase and pectinnase can increased the extract rate and content of antioxidant from the Koji, and the antioxidant activity of the extract improved. As pectinase was added, the antioxidant activities of extract are the best. The extract contained 7.5 mg/ml polypeptides, 1.4mg/ml polysaccharide, 2.0mg/ml polyphenol, 6.5μg/ml flavones,which has high antioxidant activities in different system, the IC50 were 21.5μl, 0.21ml and 0.49ml in ABTS+, DPPH·free radical and pyrogallic acid auto-oxidation system , respectively. 0.1ml of the extract can scavenged 49.2% OH·free radical, and the reduce power reach 0.732 with 0.2ml of the extract。...