Fermentation Process And Activity Of Soybean And Corn Peptides

In order to compositly utilize plant protein and improve its nutrition value. Thearticle explored that soybean and corn gluten meal were mixed and inoculated withBacillus subtilis to produce composite peptides from soybean and corn protein. Andeffects of preparation process, purification process, oxidation resistance and nitritescavenging were studied. These rusults contributed to scientific referrence for deepmanufacture and application of soybean and corn gluten meal.1. In order to improve Bacillus subtilis protease enzyme activity, Bacillus subtilismedium conditions were optimized by using response surface design. Plackett-Burman design experiments selected cultivation temperature, peptone, inoculumvolume and bottled amount from nine factors as the conspicuous ones. Taking theanalysis Bacillus subtilis enzyme activity curve into account, cultivation temperatureand time were30℃,42h. Steepest ascent test seeking to the optimize area,Box-Behnken response surface experiments were designed and analysised, optimalresults were peptone of3.0g, inoculum volume of3%(mL/mL), bottled amount of45mL. Under these conditions, Enzyme activity of this medium was (1354.23±23.05)U/mL, which were consistent with theoretical prediction values basically.2. In order to add value of plant protein，preparing soybean and corn compositepeptides via microbial fermentation. Soybean and corn composite peptides liquid-statepreparation conditions were studies by response surface method central compositedesign. Optimized liquid-state fermentation conditions was fermentation temperatureof37℃, shaker speed of184r/min, fermentation time of51h, inoculum volume of4%(mL/mL). Under these liquid-state fermentation conditions, degree of hydrolysisof protein was (25.73±1.78)%and peptide conversion rate of (33.23±1.06)%, whichwas consistent with theoretical prediction values basically.3. Crude extracts of soybean and corn composite peptides from liquid-statefermentation was purified, study on purification for static adsorption and dynamicdesorption by using DA201-C macroporous adsorption resins. The results showed thatthe preferred resin static adsorption and desorption conditions were adsorption time of12h, solid-liquid ratio of1:20, adsorption temperature of25℃, pH of5anddesorption time of15h, ethanol concentration of75%. Step gradient desorptionshowed effluent of75%of ethanol was higher absorbance values. Only75%ofethanol dynamic elution, elution volume selected140mL preferred.4. Molecular weight of soybean and corn composite peptides was roughly exploredby Tricine-SDS-PAGE electrophoresis, which was estimated molecular weights distributebetween1.0~3.0KD.5. In order to investigate the influence oxidation resistance of the ethanol concentration on the dynamics elution effluent, DPPH radical scavenging, hydroxylradical scavenging, ABTS+radical scavenging and reducing power were used toevaluate soybean and corn composite peptides, which was purified. The resultsdemonstrated that soybean and corn composite peptides of reducing power wasstronger by75%of ethanol elution, DPPH radical scavenging was stronger by50%ofethanol elution, and both were lower than0.2mg/mL ascorbic acid solutionantioxidant activity. Droxyl radical scavenging was stronger50%of ethanol elution.The influence of ethanol elution on ABTS+radical scavenging was not veryconspicuous.6. Soybean and corn composite peptides has a certain nitrite scavenging function, IC50was1.0824mg/mL。The better conditions of soybean and corn composite peptides clearednitrite was concentration of2.0mg/mL, reaction time of30min, reaction temperature of50℃,pH of2. Under these conditions,2.0mg/mL soybean and corn composite peptides solutionnitrite scavenging was64.43%，lower than the same concentration ascorbic acid solutionnitrite scavenging.