Optimization Of Lactobacillus Rhamnosus LR-CC High Density Fermentation Process And Application In Corn Straw Silage/Yellow Silage

Straw resource is abundant in China,about 700 million tons of straw can be collected for agricultural and industrial utilization annually,including more than 200 million tons of corn straw.The main utilization ways of corn straw include fertilizer,raw material,energy,material and feed.Forage conversion is one of the important methods of high value utilization of straw resources,among which silage and yellow silage are the main methods of corn straw conversion.However,due to the lack of efficient silages and yellow silages strain and complex microbial flora,the application of corn straw were limited.In this paper,a high-density fermentation technology was used to prepare Lactobacillus rhamnosus LR-CC,which was compounded with Lactobacillus plantarum and Saccharomyces cerevisiae to develop the compound agent,which was used in the development of corn silage and corn straw yellow silages,providing the accumulation of strains and fermentation technology for straw silages and yellow silages.The research results are as follows:（1）Lactobacillus rhamnosus is one of the important members of the probiotics family.It can colonize in the intestinal tract,assist the elimination of harmful substances,and improve human immunity,which has attracted widespread attention.In this study,Lactobacillus rhamnosus LR-CC（hereinafter referred to as LR-CC）was selected as the starting strain.On the basis of single factor test,response surface methodology was used to optimize its nutritional conditions,aiming to provide basic data for industrial production of LR-CC.The results showed that the optimal medium formula was glucose 20 g/L,yeast extract 20 g/L,Mg SO₄0.4 g/L,KH₂PO₄2 g/L,CH₃COONa 5 g/L,（NH₄）₂HC₆H₅O₇2 g/L,Tween 80 1 g/L,anaerobic culture at37℃for 18 h.Under these conditions,the viable number of LR-CC was up to 3.70×10¹⁰CFU/mL,which was 67 times higher than that of the original MRS liquid medium.（2）The whole corn at wax-ripe stage was treated as the control group（CK）by anaerobic fermentation for 45 days,and the whole corn at wax-ripe stage was inoculated with different compound bacterial agents at a ratio of 1%,and the anaerobic fermentation lasted for 45 days.The results showed that after silage,the optimal silage was obtained by combining Lactobacillus rhamnosus,Lactobacillus plantarum and Saccharomyces cerevisiae,and the lowest pH was3.54.There was no significant difference in water content among all groups（P>0.05）.The content of dry matter（DM）was 29.92%.Neutral detergent fiber（NDF）and acid detergent fiber（ADF）contents were the lowest,which were 40.12%and 29.43%,respectively.The contents of lactic acid（LA）and acetic acid（AA）were significantly higher than those in CK group and other groups（P<0.05）,which were 2.06 g/kg and 1.63 g/kg,respectively,but there was no significant difference in formic acid content among all groups（P>0.05）.The contents of aflatoxin B₁（AFB₁）and zearalenone（ZEN）were significantly lower than those in CK group and other groups（P<0.05）,which were 3.25μg/kg and 102.45μg/kg respectively.（3）In the control group（CK）,45 days of anaerobic fermentation of crushed corn straw without bacterial agent was taken as the control group（CK）.Different compound bacterial agent was inoculated to crushed corn straw at 1%ratio,and the anaerobic fermentation lasted for 45days.The results showed that the optimal yellow storage diet was obtained by combining Lactobacillus rhamnosus,Lactobacillus plantarum and Saccharomyces cerevisiae after yellow storage,with excellent sensory evaluation,the lowest pH was 3.64,and there was no significant difference in water content among all groups（P>0.05）.DM content was the highest（30.16%）.The content of NDF and ADF was 42.93%and 31.27%,respectively.LA and AA contents were significantly higher than CK group and other groups（P<0.05）,which were 1.78 g/kg and 1.42g/kg respectively,but there was no significant difference in formic acid content among all groups（P>0.05）.The contents of AFB₁and ZEN were significantly lower than CK group and other groups（P<0.05）,which were 4.35μg/kg and 120.46μg/kg respectively.To sum up,this study draws the following conclusions:The optimal medium formula of Lactobacillus rhamnosus LR-CC was glucose 20 g/L,yeast extract 20 g/L,magnesium sulfate0.4 g/L,dipotassium hydrogen phosphate 2 g/L,sodium acetate 5 g/L,diammonium hydrogen citrate 2 g/L,tangut80 1 g/L,anaerobic culture at 37℃for 18 h.The compound addition of LR-CC with,Lactobacillus plantarum and Saccharomyces cerevisiae to green/yellow storage can significantly reduce the pH of the feed,provide an acidic environment,reduce the content of NDF and ADF,and reduce the content of AFB₁and ZEN toxins,and improve the nutritional value and safety of the feed.