Influence of culture pH on freeze-drying viability of Oenococcus oeni and its relationship with fatty acid composition

To achieve successful malolactic fermentation in wine making, expanding interest in ready-to-use concentrated Oenococcus oeni starter culture has placed greater emphasis on developing starter production and preservation methods. The effect of growth factors on the survival of the O. oeni cells after lyophilization and its relationship with the membrane fatty acid composition were investigated. O. oeni cells in the early stationary phase survived better after freeze-drying than those in the mid-exponential phase, and those early stationary phase O. oeni cells cultured in designed ATB, FMATB and MATB growth media with different pH buffering capabilities exhibited different freeze-drying viabilities. Results concerning both membrane fatty acid composition and freeze-drying viability of O. oeni cells grown in those three media at initial culture pH 4.8, 4.0, 3.5, 3.2 were subjected to correlation analysis, indicating a decrease of the growth pH improved the freeze-drying survival of O. oeni cells, which was correlated with the enrichment of C19cyc11 and the decrease of C16:0 in the membrane lipids. A better understanding of the mechanisms of O. oeni resistance to lyophilization could rationalize their exploitation to prepare commercial starter cultures.