Study On Screening For Lactic Acid Bacterium With High EPS-producing Capacity And Optimization Of Culture Condition From Koumiss In Xin Jiang

21Lactobacillus strain was screened from koumiss in Urumqi Shuixi-gou and Ili Zhaosu, they respectively belonged to Lactobacillus helvericus (3strain)、Lactobacillus delbrueckii(3strain)、Lactobacillus casei(6strains)、Lactobacillus plantarum (6strains)、Lactobacillus acidophilus (3strains) by the observation of morphological characters、experiment of physiological and biochemical、experiment of sugar fermentation.2Lactobacillus strain with High EPS-producing Capacity were screened by determining EPS yield of Fermentation Broth with the Phenol-H2SO4method.16SrDNA molecular sequencing method was adopted to analyze the sequences of gene. Results showed that both of2Lactobacillus strains were Lactobacillus casei Zhang.In order to improve the production of EPS on Lactobacillus casei Zhang, culture condition about the Lactobacillus casei Zhang by the method of response surface was reached. On the basis of the single factor tests, Plackett-Burman tests showed that the addition of Glucose、 culture time and inoculation amount were main factors, and the optimum culture conditions were culture time of26h, inoculation amount of1.6%and addition of Glucose19g/L by Box-Behnken tests. Under these optimal conditions, the yield of EPS increased by47.7%as compared with the initial medium and production of EPS reached up to151.76mg/L.Research on the fermenting capability of Lactobacillus casei Zhang, the mare milk was fermented which take the Lactobacillus casei Zhang as starter. Results showed that the titration acidity was96.03°T, pHwas4.41and the viscosity was220mpa.s after inoculating Lactobacillus casei Zhang in mare milk and incubation for15h at37℃.The antioxidant activity of polysaccharides from Lactobacillus casei Zhang was evaluated by scavenging capacities against DPPH、·OH and02-·free radicals. Results showed that when the concentration of2.75mg/mL, the DPPH and-OH radicals-scavenging acticities of the EPS are28.9%and62.34%. When the concentration of EPS was2.75mg/mL, the clearance rate to O2-·was68.4%. It showed that the EPS of Lactobacillus casei have good ant-oxidative effect.