Biodiversity of autochthonous Oenococcus oeni strains isolated from Apulian wines

Winemaking is a complex process that involves two different fermentation steps: alcoholic fermentation (AF) and malolactic fermentation (MLF). MLF consists in a decarboxylation of L-malic acid to L-lactic acid and leads to increase in wine pH, decrease in wine sourness, increase of microbial stability and bacterial production of various secondary metabolites that contribute to wine quality. Usually MLF is performed by lactic acid bacteria, mainly Oenococcus oeni strains, inoculated at high concentrations, enough to ensure survival and malolactic activity. O. oeni strains shown a large degree of phenotypic and genotypic heterogeneity. In this work, we studied the genetic and technological diversity of O. oeni strains isolated from Apulian wines undergoing spontaneous MLF to select strain suitable for autochthonous malolactic starter cultures design. We studied the genetic diversity of 50 O. oeni strains using two molecular methods (Variable Number Tandem Repeat-VNTR and Multi Locus Sequence Typing-MLST), and malolactic performances. VNTR identified 30 profiles, of which 11 unique profiles, while MLST distinguished only 8 different sequence types (STs) among 20 strains, resulting have different VNTR profiles. Nevertheless MLST techniques allowed to find six new STs and two new alleles, respectively, for gene rpoB and purK. This study confirmed the worldwide presence of two O. oeni phylogenetic subpopulations (A and B). All the strains have been screened for their capacity of degrading malic acid, with two different times of bacterial inoculum, either together with yeast (co-inoculum) or after the completion of alcoholic fermentation (sequential inoculum). O. oeni strains studied shown different malolactic performances. Experimental scale-up allow us to select two O. oeni strains as potential biotypes for starter cultures.