Carbohydrate metabolism in Oenococcus oeni: a genomic insight

Abstract Background Oenococcus oeni is the bacterial species that drives malolactic fermentation in most wines. Several studies have described a high intraspecific diversity regarding carbohydrate degradation abilities but the link between the phenotypes and the genes and metabolic pathways has been poorly described. Results A collection of 41 strains whose genomic sequences were available and representative of the species genomic diversity was analyzed for growth on 18 carbohydrates relevant in wine. The most frequently used substrates (more than 75% of the strains) were glucose, trehalose, ribose, cellobiose, mannose and melibiose. Fructose and L-arabinose were used by about half the strains studied, sucrose, maltose, xylose, galactose and raffinose were used by less than 25% of the strains and lactose, L-sorbose, L-rhamnose, sorbitol and mannitol were not used by any of the studied strains. To identify genes and pathways associated with carbohydrate catabolic abilities, gene-trait matching and a careful analysis of gene mutations and putative complementation phenomena were performed. Conclusions For most consumed sugars, we were able to propose putatively associated metabolic pathways. Most associated genes belong to the core genome. O. oeni appears as a highly specialized species, ideally suited to fermented fruit juice and more specifically to wine for a subgroup of strains

Selection criteria and tools for malolactic starters development: an update

The use of malolactic starter cultures to improve the fermentation process and enhance wine quality and safety is becoming a common winemaking practice, increasingly preferred to spontaneous fermentation. Given its great oenological properties, Oenococcus oeni is the species most present in commercial brands of wine lactic acid bacteria (LAB) starters. Stress resistance, technological performances and safety are the key selection criteria to take into account when designing effective malolactic starters. Nowadays, new LAB strains are selected by exploiting advanced technological applications rather than the traditional screening methods based on a trial and error approach. In particular, the progress made in the fields of genetics and molecular biology, as well as in the whole genome sequencing projects, offers new tools to better characterize candidate starter strains. This review aims at providing an updated picture of the technological approaches that should be used to select LAB strains suitable for winemaking. In the near future, the full integration of phenotypic and genetic data will make it possible to rationally develop malolactic cultures that are specific for different types of wine