Evidence for exopolysaccharide production by Oenococcus oeni strains isolated from non-ropy wines

Aims: The aim of this study was to assess the exopolysaccharide (EPS) production capacities of various strains of Oenococcus oeni, including malolactic starters and strains recently isolated from wine. Methods and Results: Fourteen O. oeni strains displaying or not (PCR check on genomic DNA) the gtf gene generally associated with beta-glucan formation and ropiness were grown on grape juice medium, dialysed MRS-derived medium or synthetic medium. The soluble polysaccharides (PS) remaining in the culture supernatant were alcohol precipitated, and their concentration was quantified by the phenol-sulfuric method. Most of the O. oeni strains studied produced significant amounts of EPS, independently of their genotype (gtf+ or gtf-). The EPS production was not directly connected with growth and could be stimulated by changing the growth medium composition. The molecular weight distribution analysis and attempts to determine the PS chemical structure suggested that most strains produce a mixture of EPS. Conclusion: Oenococcus oeni strains recently isolated from wine or cultivated for many generations as a malolactic starter are able to produce EPS other than beta-glucan. Significance and Impact of the Study: These EPS may enhance the bacteria survival in wine (advantage for malolactic starters) and may contribute to the wine colloidal equilibrium.