Simulated microvinifications were conducted in aseptic red must with malic acid at pH 3.5 in order to evaluate the effect of some stress compounds present in wine, such as sulfur dioxide, dodecanoic acid, and copper, on the population dynamics of Oenococcus oeni strains and malolactic fermentation. After standard inoculation of a yeast strain, three strains of O. oeni were inoculated, individually and in mixed culture, to obtain initial bacterial populations of 102 cfu/mL for simulating actual vinifications. Throughout alcoholic and malolactic fermentations, population dynamics of O. oeni strains were monitored by multiplex random amplified polymorphic DNA-PCR. The simulated microvinifications allowed us to compare the strains and analyze how they behaved in the presence of the stress compounds. Of the three strains assayed, a commercial strain and one isolated in the cellar were more tolerant and efficient than the type culture strain. The presence of the stress compounds produced delays in malolactic fermentation and a reduction on the cell growth of all strains. The most inhibiting stress compound was dodecanoic acid. In the mixed culture, all stress compounds delayed malolactic fermentation by 7 days with respect to the control. The procedure used in this research may provide more information about the behavior of malolactic strains in various conditions.
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