Evaluation of express level of mleA gene in Oenocuccs oeni under different experimental conditions

Malolactic fermentation usually occurs simultaneously or after alcoholic fermentation and is known to improve wine quality trough deacidification, production of desirable flavors and aromas, and enhancement of microbial stability. In this study we developed a RT-qPCR (reverse transcription quantitative PCR) method to evaluate the gene expression levels of mleA gene in Oenococcus oeni, in a synthetic medium, under different experimental conditions such as different concentrations of malic acid, ethanol, lactic acid. Samples were collected four times a day until the end of malolactic fermentation, and subjected to plate count evaluation, RT-qPCR and enzymatic assays for malic and lactic acid determination, sugars and ethanol. All trials were carried out in triplicate. Gene expression levels were calculated using the MNE (mean normalized expression) method, according to the MIQE. Results show that in absence of malic acid mleA gene expression remains stable at a baseline level, while in presence of malic acid and ethanol the expression profile shows a positive peak at the moment of maximum slope of the curve of decrease in concentration of malic acid. Conversely, in presence of lactic acid the expression profile is stable to the baseline level. In conclusion, ethanol do not affect the gene expression profile, while lactic acid seems to be involved in gene regulation of mleA.