Screening Of Enshine Lactic Acid Bacteria And Its Application In Fermented Milk

Taking Gansu, Xinjiang, Inner Mongolia and other northern peasant homemade fermented food as the research object. Though repeatedly crossed separated and screened by the TJA plate and yogurt fermentation experiment, obtained the excellent fermentation performance of lactic acid bacteria strains. Determined these strains in the fermenting whether have polysaccharide by phenol-suLfuric acid method and ethanol precipitation, and selected ten strains produced exocelluLar polysaccharide (Exopolysaccharides abbreviation EPS) high strain, then through acidoresistant resistance and bile salts experiment, further screened a good JNG strain with comprehensive performance. Strain JNG was identified that it belonged to Enterococcus durans. In order to improve the EPS yield, this paper studied the effct of the output medium components and cuLtivating conditions on the bacteria JNG growth and EPS yield influence. The resuLts showed that the best medium composition of bacteria JNG: tomato juice 50mL, yeast extract powder 5g, K2HPO4 2g,peptone 20g, lactose 50g, sodium acetate 5g, twain - 80 1mL, ZnSO4·7H2O 0.03g,CaCO3 2g,distilled water 1000mL. The bset optimum cuLture conditions of bacteria JNG: kind of age 3.5 h, temperature 38℃,initial pH 8, inocuLation amount of 6%.The water-soluble polysaccharide of purified strain JNG after ethanol precipitation though Sephdex G-100 column chromatography, control flow velocity 0.2 mL/min, 0.2 mL/tube, and got other type symmetrical peak alone. then took the collection of the eluen into the Sephdex G - 200 column chromatography, still couLd get single type symmetrical peak michmash. But the characteristics of protein existed under 280nm uLtraviolet absorption, it can specuLate that portion lamellarins may be the form of proteoglycans, the separation of polysaccharide solution is more complicated, and yield is too low, so this thesis wouLd not be further research.High serum cholesterol is the one of the main pathogenesis that causes the human mortality high cardioascuLar disease in the world. Probiotics play in adjusting bowel and various functions, at the same time can achieve pure lower cholesterol but not affect other nutrient absorption effect, therefore it has attracted the attention of the world related field. Looking for, screening and optimizing a cholesterol function of probiotics and screening vitroly probiotics in scientific method to ensure probiotic organisms the efficacy, safety and quality stability and product development are important role. The research resuLts show that: the further define the method of the ammonium ferric already screening of lactic acid bacteria isolated, screened a plant with high cholesterol removal rate is the candidate strains strains appraisal, and undergo E2 determined for streptococcus thermophilus cuLtured strains. For candidates in further strain acid resistance and bile salts ability and other biological characteristics investigation found that the candidates to antibiotics strains E2 also has relatively stable advantage, so as to further research. This paper studied the effct of the output medium components and cuLtivating conditions on the bacteria E2 growth influence. The resuLts showed that the best medium composition of bacteria E2: tomato juice 50mL, glucose 2g, yeast extract powder 5g, K2HPO4 2g, beef anointed 10g, lactose 20g, sodium acetate 5g, twain - 80 1mL, ZnSO4·7H2O 0.04g,MgSO4·7H2O 0.6g, CaCO3 0.25g,distilled water 1000mL. The bset optimum cuLture conditions of bacteria E2: kind of age 3.5 h, temperature 41℃, initial pH 8, inocuLation amount of 2%. Finally application in yogurt fermenting for bacteria E2. ResuLts showed that: when the number of the ratio of candidate strain E2 and laboratory strain D2 was 1:1 , yogurt fomated was very good.