Genetic and physiological studies on Oenococcus oeni PsuI in response to ethanol stress

Malolactate fermentation (MLF), which is known to decreases total acidity and improves the stability and quality of cider is conducted by Oenococcus oeni; the principal microorganism responsible for MLF under stress conditions. Understanding O. oeni physiology in stress conditions can be used to generate tools based on molecular and physiological approaches allowing more precise characterization of strains. Regarding intracellular protein, the results showed an increase in the levels of amino acids under ethanol stress. To study the expressed genes under ethanol stress, one gene were sequenced. An outer-membrane lipoprotein carrier protein precursor, Lo1A was expressed under ethanol stress conditions. Scanning electron microscopy was used to study the effect of ethanol stress on cell morphology. SEM revealed aggregation of bacterial cells as the level of ethanol increases in culture medium in comparison to controls.