Characterization Of Starch Degrading Bacteria And Its Application In Ensiling High-moisture Corn

Starch is the main energy-supplying substance in ruminant concentrates.Increasing the degradation rate of starch can save feed costs and promote protein absorption.Microbial degradation is one of the effective methods to improve starch utilization.In this study,by separating starch-degrading microorganisms from silage,analyzing the degradation ability of each strain on feed starch,optimizing the fermentation and culture conditions of the preferred strains,determining the relevant enzyme activity indicators of the strains,and applying the preferred starch-degrading strains to bagged Ensiling high-moisture corn fermentation,the fermentation index of high-moisture corn silage were measured,and the effect of adding starch degrading bacteria on the fermentation of grain corn was determined.Seven strains of strains were preliminarily selected from the soil and several high-quality whole plant corn silage samples,and then trypan blue medium was used as the secondary screening medium,and the secondary screening was performed according to the presence or absence of the hydrolysis circle to obtain three strains of starch-degrading microorganism Strains.It was identified as Sphingobium yanoikuyae,Paenibacillus polymyxa,and Enterobacter tabaci.The starch degradation ability of the strains was determined by the starch degradation rate,α-amylase activity of the three strains screened and the size of the hydrolysis circle of the starch coloring medium.Starch degradation rate,α-amylase activity and hydrolyzed transparent circle size all show that the ability of Bacillus polymyxa MS to degrade starch is the strongest,the starch degradation rate is as high as 92%,and α-amylase activity reaches the highest in 48 hours of fermentation culture,The highest enzyme activity is 8659 U·L-1,and the diameter of the transparent hydrolysis ring is 15 mm.Therefore,the fermentation conditions of Bacillus polymyxa MS were optimized.The optimization results showed that the best basic culture medium was C culture medium,the best fermentation condition was p H 4,the culture temperature was 31℃,the rotation speed was 140r·min-1,and the fermentation time At 24 h,the volume of liquid was 100/150 ml,and the inoculation volume was 4%.Bacillus polymyxa MS with strong starch degradation ability after screening and optimization was used as a high-moisture corn silage fermentation agent.Samples were analyzed with silage fermentation time to analyze silage microbial dynamics,starch degradation and aerobic stability.Microbial analysis found that the biomass of lactic acid bacteria and Bacillus significantly increased during the silage fermentation of Bacillus polymyxa MS（p<0.05）,the highest number of lactic acid bacteria was 7.2×108CFU·g^-1,and the highest number of Bacillus was 8.3×108 CFU·g^-1;There is also an inhibitory effect on the growth of mold.It has obvious influence on starch and reducing sugar content during silage fermentation.The addition of strain MS has a significant（p<0.05）degradation effect on starch.At the end of silage,the starch content of the test group was 11 percentage points lower than that of the control group（respectively 66%,77%）;the reducing sugar content of the experimental group in the late silage fermentation period increased faster than that of the control group.At the end of fermentation,the reducing sugar content of the experimental group reached the maximum,1.06% DM and 4.2% DM,respectively.There was no significant difference between the experimental group and the control group in maintaining aerobic stability.The silage temperature of the experimental group was 2℃ higher than the ambient temperature for only 1 d longer than the control group.The addition of strain MS had no significant effect on the silage fermentation dry matter storage rate and p H.At the end of fermentation,the dry matter preservation rates of the treatment group and the control group were 92% and 88%,respectively.In summary,Bacillus polymyxa MS can effectively degrade starch in the process of high-moisture corn silage,promote starch degradation rate,increase the content of reducing sugar in high-moisture corn silage,and promote feed utilization.