High Yielding Of Exocellular Poly-saccharide And Tolerability Of Lactobacillus Delbrueckii Subsp.bulgaricus NCFB 2772

It has been caused attention by many domestic and foreign scholars about EPS produced by LAB with unique physiology function and application value,and it has been a hot issue to tolerability of probiotics exposed to bile salt and antibiotics.L.burlgaricus NCFB 2772 was selected as EPS biosynthesis strain.Optimizing of nutrition conditions and culture condition of L.burlgaricus NCFB 2772 synthesised EPS,research of cells' tolerability were main contents.The research results are as follows:A single factor experiment results of several factors affecting EPS synthesis were shown:The EPS synthesis quantity was highest when initial pH value was 6.5,fermentation temperature was 40?,inoculation amount was 4.5%,stirring speed was0 rpm,fermentation time was 18 h.To further improve the production of EPS,Compared to several suitable fermentation medium of L.burlgaricus NCFB 2772.we have further optimized the influence of carbon nitrogen source,carbon and nitrogen source proportion,and different juice additives to L.burlgaricus NCFB 2772's EPS.The results were : EPS synthesis quantity wan highest when source of carbon was fructose,nitrogen source was tryptone,carbon nitrogen ratio was1.5:1.0,apple juice additives was 6%.Response surface method was a statistical method by solving the problem with reasonable experiment design.The test of three factors and three level response surfa ce analysis about L.burlgaricus NCFB 2772's EPS,regression equation was C4 =-287.08 +39.83 C1 +11.44C2+18.54C3,Optimal cultivation condition was initial pH value was 6.5,fermentation temperature was 42?,inoculation amount was 4.5%.Leading indicator of probiotics was the activity and tolerability of lactic acid bacteria.The results of L.burlgaricus NCFB 2772's tolerability research were L.burlgaricus NCFB 2772 can exposed to pH=2.5 of gastric juice,the effect of intestinal juice was not obvious,bile salt has greater influence on its activity,living/dead rate of L.burlgaricus NCFB 2772 when it exoposed to different dosesvancomycin was 65.71%,The tolerability of L.burlgaricus NCFB 2772 was very well when the concentration of vancomycin was 0.1mg/ml.