Beneficial Microbes: Food, Pharma, Aqua & Beverages Industry

Biography

Biography: Marguerite DOLS-LAFARGUE

Abstract

Wine lactic acid bacteria (Lactobacillus, Pediococcus, Leuconostoc and Oenococcus) generally multiply after alcoholic fermentation and consume the elements left by the yeast (sugars, acids). They drive the malolactic fermentation (MLF) which improves the taste and overall quality of wine. Despite the accumulation of knowledge, MLF is still a difficult step in the winemaking. Selected malolactic starter cultures have thus been developed. According to their characteristics, they can be introduced into the wine at the end or during alcoholic fermentation, but implantation failures are still frequent: MLF may be initiated by the starter, then stopped or led by the native flora, with the risk that the dominant native strains induce beverage alteration. On the other hand, several wine lactic acid bacteria, especially Pediococcus parvulus and Oenococcus oeni, have been described exopolysaccharides producers. O. oeni is the bacterium that most frequently performs MLF in temperate areas, while P. parvulus is rather considered an agent of alteration, because many strains cause wine ropiness. This alteration is linked to the accumulation of -glucan in the wine. The polymer synthesis is catalyzed by a glucosyltransferase Gtf, encoded by the gtf gene. A detailed study has shown that this gene fairly widespread among wine lactic acid bacteria. Besides, in O. oeni, many other genetic determinants associated with the production of exopolysaccharides have been identified and associated with more "discrete" phenotypes. Instead being detrimental to wine quality, these polymers may, in the future, being valued in several ways: (i) their presence may allow the development of more robust malolactic starters and (ii) from the organoleptic point of view, the wines naturally containing polysaccharides often display decreased astringency and increased fullness, body and round sensation.