Abstract
Ethanol acclimations have been proven to be beneficial for enhancing the viability of lyophilized Oenococcus oeni. To explore the relevant mechanisms, cell integrity, protein patterns, morphology, exopolysaccharides (EPS) content of lyophilized O. oeni SD-2a with ethanol acclimations were investigated in this research. After freeze-drying, the improvement of cell integrity was found in all ethanol acclimated cells. Comparative proteomics combined with bioinformatics revealed the important role of central carbohydrate metabolism, polysaccharides production, cell envelope biosynthesis and stress responses related proteins with ethanol acclimations in freeze-dried O. oeni SD-2a. Extracellular polymeric substances were observed in mild ethanol (5% and 8%) adapted cells using scanning electron microscope. In addition, mild ethanol (5% and 8%) adapted cells showed higher EPS content. Transcriptional analysis showed that citrate lysis gene over-expressed in all ethanol acclimated freeze-dried cells. Therefore, citrate was added in culture medium and it is highlighted that the addition of citrate was useful for the growth of freeze-dried O. oeni SD-2a. These results provide new insights of molecular mechanisms regulated by ethanol acclimation and improve our understanding of biological characteristics involved in freeze-dried O. oeni.
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