Diverse physiological and metabolic adaptations by Lactobacillus plantarum and Oenococcus oeni in response to the phenolic stress during wine fermentation

Understanding the mechanisms of combating phenolic stress in wine is important for optimization of starter culture for improved competitiveness. The cellular membrane adaptations, as well as metabolic transformations driven by malo-lactic starter cultures, i.e. Lactobacillus plantarum (Lp2565) and Oenococcus oeni (O02219) with response to wine phenolic compounds were studied. The morphological changes based on scanning electron microscopy indicated the higher tolerance of O02219 to phenolic stress than Lp2565. Further, the fatty acid profiling suggested that the membrane fluidization in Lp2565 was attributed to higher unsaturated fatty acids whereas the rigidification in O02219 was by incorporation of saturated fatty acid in the membrane. The metabolic transformation of phenolic compounds suggested that Lp2565 has more versatile phenolic detoxification enzyme systems compared to O02219. The metabolic conversions resulted in degradation of phenolic compounds into volatile phenols, aromatic alcohol, and phenyl propionic acids, thus indicating the possible involvement of oxidoreductases, decarboxylases, and demethylases.