The effects of alcohol stress treatment on physiological properties of Oenococcus oeni SD-2a

Abstract:

To obtain high efficiency of MLF starter cultures, the effects of alcohol stress treatments on the growth, intracellular malolactic enzyme (MLE) activity, freeze-drying viability, and membrane fatty acid composition of Oenococcus oeni SD-2a strain were studied. The results showed that alcohol stress treatments did strongly decrease bacterial growth rate and cell biomass, but increased distinctly MLE activity. Compared with control treatment, 5% alcohol stress treatment decreased bacterial freeze-drying viability, and 10% alcohol stress treatment increased bacterial freeze-drying viability. Concerning the membrane fatty acid composition, it was observed that the unsaturated : saturated fatty acid ratio in the former treatment is 1.12, which is lower than that of control by 26.3%, and the unsatu-rated : saturated fatty acid ratio in the latter treatment is 2.28, which is higher than that of control by 50.6%. So it was assumed that O. oeni SD-2a adopted different adaptive mechanisms in the membrane levels under different alcohol stress conditions, and its membrane fatty acid composition might have a close relationship with bacterial freeze-drying viability.

Key words:Oenococcus oeni;Alcohol stress;Membrane fatty acid;MLE activity