Microbial Screening Of Soybean Meal Fermentation And Optimization Of Mixed Fermentation Conditions

In this study,a variety of microorganisms with high yield of protease,amylase and cellulase were screened from natural fermented soybean meal.After the identification of strains,the more suitable strain combination was screened through antagonistic experiments and safety tests.Using crude protein content and soybean peptide content as evaluation criteria,the fermentation conditions of single microbial strains were optimized.The optimal fermented strain combination was screened,the mixed fermentation process conditions were optimized and the changes of nutrient content and ANFs before and after solid-state fermentation of soybean meal were analyzed.The results showed that:22 strains were separated and purified from natural fermented soybean meal,including 17 strains of bacillus,3 strains of yeast and 2 strains of mold.The activity of Bacillus B-8’ s producing protease,amylase and cellulase was higher than those of other strains by measuring the activity of producing protease,amylase and cellulase.The activity of Saccharomyces Y-3’ s producing enzyme was also stronger than that of the other two yeasts.Both Mold M-1 and M-2 had good enzyme production activity.After the strains were identified,Bacillus B-8 was Bacillus subtilis B-8,Saccharomyces Y-3was Saccharomyces cerevisiae Y-3,Mold M-1 was Rhizopus oryzae M-1 and Mold M-2was Penicillium chrysogenum M-2.The four strains were safe strains and do not inhibit each other,and could be used for solid-state fermentation tests..Through the fermentation test of single microbial bacterias,the optimal fermentation conditions of single microbial bacterias were: 10% of inoculation quantity,1.0:1.4 of the ratio of material to water,32°C of fermentation temperature and 72 h of fermentation time.Under the optimal single microbial bacteria fermentation conditions,soybean peptide content was highest(P<0.05)in fermented soybean meal by Bacillus subtilis B-8;crude protein content in fermented soybean meal by Rhizopus oryzae M-1was highest(P<0.05).Bacillus subtilis B-8 and Rhizopus oryzae M-1 were the optimal fermentation strain combinations by comparing the fermentation results of multi-strain combination.The best mixed fermentation process conditions were: Bacillus subtilis B-8and Rhizopus oryzae M-1 were connected to soybean meal simultaneously,the ratio of inoculation of the two strains was 2:1,the total amount of inoculation was 10%,the fermentation temperature was 40°C,the ratio of material to water was 1.0:1.4,and the fermentation time was 96 h.After mixed fermentation of soybean meal,the content of soybean peptide,crude protein,crude ash,and crude fat in the fermentation products were all significantly increased(P<0.05).Compared with that before fermentation,the water content decreased significantly(P<0.05),macromolecular proteins can be broken down into micromolecular proteins below 10 ku,and the content of glycinin,β-Conglycinin,and trypsin ihhibitor was significantly lower than that of unfermented soybean meal(P<0.05).The results showed that the nutrient content of soybean meal increased significantly after the mixed fermentation,the content of antinutritional factors decreased significantly and the nutritional quality had been improved.