Study On Soybean Antioxidative Peptide From Solid-state Fermentation Of Soybean Meal

Soybean antioxidant peptide (soybean protein hydrolysate) was composed ofsmall molecular peptide, and had the anti-fatigue, delay aging body, regulatingimmunity and reduce cholesterol and other physiological function. That was a kind ofimportant functional polypeptide. In this study, by using Bacillus sp. in solid-statefermentation of soybean meal, the fermentation conditions were optimized, theantioxidant activity was analyzed, and the methods of extraction and purification forantioxidant peptide, determination of its molecular weight were further studied. Themain research contents and results are as follows:1. With the single factor experiment analysis and Box-Behnken response surfacemethodology, conditions of soybean meal solid-state fermentation were carried outusing the total antioxidant activity (T-AOC) and the content of polypeptide asevaluating indicators. The result showed that the best fermentation conditions were asfollows: inoculation amount9.6%, ratio of material to water1:0.9, fermentationtemperature35℃. Soybean meal was fermented for48h under the optimumconditions, T-AOC was from207.2U/g to1091.1U/g and the content of polypeptidewas from21.0mg/g to347.7mg/g, respectively increased by4.3times and15.6times.The experimental value was basically agreed with the predictive value. T-AOC andthe content of polypeptide were highly correlated (R2=0.8604), it indicated thepolypeptide was antioxidant peptide.2. In order to study the antioxidant activity of fermented soybean meal, the totalantioxidant activity, hydroxyl free radical scavenging rate, and superoxide anionscavenging rate were measured for different concentrations of raw soybean meal,fermented soybean meal and over0.22μm filter samples. The results show that thethree indicators were increased with the sample concentration. When the sampleconcentration was1.5%, the raw soybean meal, the fermented soybean meal and thefilted sample’s total antioxidant activity was27.57U,46.26U,102.98U; hydroxylradical scavenging rate was69.40%,69.10%,84.65%; superoxide anion free radicalscavenging rate was19.61%,26.14%,45.49%, respectively. Linoleic acidperoxidation resistance and DPPH free radical scavenging rate of the fermentedsamples were also increased obviously. With400μmol/L Vc as control, the resultindicated that the fermented soybean meal had strong antioxidant activity. 3. Using DEAE-Sepharose ion exchange chromatography, Sephadex G-25gelfiltration chromatography for over0.22μm filter samples, three elution peaks (I-a, I-c,Ⅳ-c) with the strongest antioxidant activity were obtained, and the total antioxidantactivity was7.4U,10.73U and3.33U, respectively. The result of Tricine-SDS-PAGEshowed that the molecular weight of I-a was below of2KD, and I-c and Ⅳ-c wereabout10KD. It indicated that the purification method was feasible, and it provided atheoretical basis for further purification.