Isolation And Enological Characterization Of Oenococcus Oeni From Chinese Wine And Energy Metabolism Of Malolactic Fermentation

L~+~4 2001 )~l#眫{~ 83 Isolation and Enological Characterization of Oenococcus oeni from Chinese Wine and Energy Metabolism of Malolactic Fermentation Doctoral Candidate: Zhang Chun hui Tutor: Prof. Li Hua College of Enology, Northwest Sci-Tech University of Agriculture and Forestry, Yangling, Shaanxi, China, 712100 Abstract The malolactic bacteria are lactic acid bacteria which carry out a secondary fermentation (malolactic fermentation,MLF) of new wine afier alcoholic fermentation. The genera of Oenococcus oeni (formly Leuconostoc oenos) have been found to carry out the malolactic fermentation most frequently and have been found to be most desirable. Apart from decreasing the acidity of wine, malolactic fermentation has two other important effects. One of these is bacteriological stability, the other is the change in flavor complexity. In general, pure culture inoculation with commercial strains are practiced to some extent in Chinese wine-making, but these strains are not always well-stuited to the low temperature and pH conditions prevalent during wine production in the Northwest of China. The possibility of using malolactic bacteria indigenous to Chinese wine intiated this study. Our objectives included isolated of Oenococcass oeni from wines active in carrying out the malolactic fermentation, characterization of such bacteria to confirm their identity and ability to decompose malate, and selection of the most active strains for possible pure culture inoculation to improve wine quality. In selection of Oenococcus oeni from wine, we have studied 10 kinds of selective culture media. The results show that the reletive detective force (RDF) value of ATB agar medium and improved MRS agar medium are highest, the two media have the best capacity to culture the bacteria from wine. In order to inhibit the growth of yeasts and molds during the isolation of Oenococcus oeni, anaerobic condition (with N2, 25-30t) can suppress mold growth, actidione and sorbic acid can suppress yeast growth, and also use vancocin to suppress the other lactic acid bacterium, such as Lactobacillzss growth. We designed the two selective media for Oenococcus oeni isolation from wine: ATB media with 5OmgIL actidione and 5Omg/L vancocin; MRS media with 10%(v/v) tomato juice, 5Omg/L actidione and 5Omg/L vancocin. With selective culture media, we have isolated 24 strains malalactic bacteria from different region wines of China, Identification of the isolates are performed according to the criteria established in Bergey c Manual of Systematic Bacteriology. The following criteria and tests are considered for isolates 84 ~~tI (Oenococcus oeni) -1~f~ taxonomical analysis: cell morphology, Gram stain, catalase production, fermentation of 20 different carbon sorces, growth depends on tomato juice factor and limus milk tests, growth at different low pHs, growth at different alcoholic concentraion(v/v, 10%, 11%, 12%), malate decomposition test. The results show that 24 isolates are also Oenococcus oeni. Differentiation of isolates are carried out by analysis of total soluble cell protein pattern and ~~-random amplified polymorphic DNA (RAPD) pattern. The results indicate that total soluble cell protein pattern can differentiate different genera but fai...