Study On The Survival Ability Of Lactic Acid Bacteria On Grass Surface And Its Effect On Silage

The epiphytic lactic acid bacteria that are present on forage crops are one of key factors of deciding the silage fermentation quality.At present,systematic researches about lactic acid bacteria on grass and forage crops,and the major factors of influencing them are lacking.Sudan grass(Sorghum sudanese)and stylo(Stylosanthes guianensis)are excellent warm-season grasses commonly grown in southern China.However,the high buffer capacity,low water-soluble carbohydrate content and a small amount of lactic acid bacteria of them often led to the silage fermentation quality poor.Therefore,this study selected three species of forage grass: sudan grass,stylo,and Bachiaria hybrid.This experiment were chosen sudan grass and stylo to research Lactic acid bacteria's viability on grasses surface,Stylo and Bachiaria hybrid were chosen to research the distribution of lactic acid bacteria under different external conditions.By analyzing the nutrient requirements for the growth of lactic acid bacteria,excellent lactic acid bacteria were selected.Therefore,Selected lactic acid bacteria were added to sudan grass and stylo for silage to improve the silage fermentation quality.The main results were as follows:Lactic acid bacteria used in this study were taken from laboratory-preserved strains.They were Enterococcus faecalis,Lactobacillus reuteri,L.brevis,Pediococcus pentosaceus,L.lactis,Leuconostoc mesenteroides,P.acidilactici,L.casei,L.plantarum,L.rhamnosus.The ability of these 10 strains to adhere to the surface of the two grasses differed depending on the species of plant and lactic acid bacteria.After spraying a certain amount of lactic acid bacteria to sudan grass and stylo surface for 72 hours,the L.reuteri was of high survivability rate on the surface of Sudan grass and lactic acid bacteria with high survivability on the surface of stylo was L.mesenteroides.After spraying different sugar solutions and lactic acid bacteria suspension on the surface of stylo and Bachiaria hybrid,the survival rate of lactic acid bacteria was higher than that of the control at each time period.After 7 days,a large number of lactic acid bacteria on the surface of Bachiaria hybrid and stylo were fructose-treated and sugar-treated respectively.Glucose was added at different contents to the MRS medium,and the growth of lactic acid bacteria was different,There was a positive correlation between the glucose content in the culture medium and the growth concentration of lactic acid bacteria.Spraying different nitrogen source solutions on stylo and Bachiaria hybrid's surface changed the survivability of lactic acid bacteria.After 7 days,a large number of lactic acid bacteria on the surface of Bachiaria hybrid and stylo were treated with 0.1%peptone-treated and 1% peptone-treated,respectively.Under different oxygen conditions,the growth capacity of lactic acid bacteria was also quite different.E.faecalis,P.acidilactici and L.rhamnosus grew better under aerobic conditions,L.reuteri and L.brevis,which grew better under anaerobic conditions.Bachiaria hybrid and Stylo under different humidity conditions,the growth capacity of lactic acid bacteria was at 80% > 60%> 40%.Through the comparison of low sugar resistance and acid resistance tests,L.reuteri,L.mesenteroides and L.rhamnosus were selected as excellent strains of lactic acid bacteria.The ensiling experiment was conducted using the screened lactic acid bacteria.The results showed that the silage effect of the treatment group added lactic acid bacteria or lactic acid bacteria and glucose was better than the control,and the glucose added treatment was superior to lactic acid bacteria alone.Among them,the addition of L.reuteri,L.reuteri and glucose was the best,but the aerobic stability was poor.