Production Of Bioactive Soybean Peptides By Fermentation Of Soybean Meal

Soy peptides, which is prepared from soy protein by chemical hydrolysis,microbial fermentation or enzymatic hydrolyze, obtained by further separation andpurification. It has good biological activity and good processing properties, which thematrix proteins unmatched. As a beneficial soybean in highly processed products, soypeptide is getting widely application in different areas increasingly, such as foodindustry, medicine, cosmetic. However, low yield and high cost are the primaryproblems that limit soy peptides market. In this paper, soybean meal was selected asoriginal material, soy peptides was prepared by fermented soybean meal with aselected strain. All the study concentrated on production technic, as a basis forsoybean meal fermentation to prepare soybean peptides, systematic researches werecarried out on fermentation conditions, clarification, decolorization, separation,antioxidative activity of soy peptides and quality of soy peptides.Bacillus subtilis which has strong ability to hydrolyze protein, was screened outfrom four strains. Taking soy peptides concentration as index, firstly, the fermentationmediums were optimized using Plackett-Burman design, steepest ascent path,Box-Behnken design, the optimal fermentation medium was obtained: soybean mealconcentration65.46g/L.the glucose concentration3.87g/L, calcium carbonateconcentration2.47g/L, The concentration of soybean peptide can reach39.47g/L atthis medium and it increased by32.67%compared with before optimization. On thebasis of optimized medium, the other fermentation conditions were optimized usedthrough signal factor experiment and the optimal conditions were: temperature37°C,rotary speed220rpm and fermentation time48h. The yield of soybean peptides canattain40.26g/L at this optimal condition. The distribution of the molecular mass ofsoybean peptide was determined and analysized by steric exclusion chromatography.Results showed that there was87.23%of soybean peptide with molecular weight inthe range of300~5000Da.The ferment liquor was decolored by active carbon, and the condition was optimized through signal factor experiment. Optimized conditions were: activecarbon dosage was4%（w/v）, time was30min, temperature was50°C. Under thiscondition, decoloration ratio was82.12%, loss ratio of peptides was19.12%.Sephadex G-15gel permeation chromatographic separation was used to separatethe soy peptides, and the separation condition was optimized through signal factorexperiment. Optimized conditions were: column height48cm, velocity of flow2mL/min, sampling amount4mL concentration of soybean peptides80mg/mL. Threecomponents were obtained under the optimized condition, ranges of molecularweights distribute were5000~1818Da,1764~1398Da,325~276Da.The antioxidant activity of different peptide component was determined in termsof inhibition of lipid peroxidation, ABTS assay, FRAP assay, ORAC assay and metalchelating activity. Proved of anti-oxidant capability: component II＞component I＞component IV. Contrast with macromolecular peptide component and enzymatichydrolysis peptide, small molecules soybean peptide has stronger anti-oxidant.Soy peptides concentration by lyophilization, of which physical and chemistryindex were analyzed. Results showed that TCA-NSI was92.56±0.75%, Resultsshowed that there was89.50%of products with molecular weight in300~5000Da.The products meet national standard (GB/T22492-2008) as the secondaryclassification of soybean peptides.