Identification of QTLs responsible for malic acid modulation

Philippe Marullo, ISVV – Bordeaux Aquitaine

In a recent study, a variety of genes controlling acidity-related behaviors of the winemaking yeast Saccharomyces cerevisiae were identified using a QTL approach. Several of them showed allelic variations affecting malic acid metabolism and pH homeostasis during alcoholic fermentation. Such alleles have been used to direct the genetic selection of innovative S. cerevisiae starters capable of acidifying or deacidifying wine by producing or consuming large amounts of malic acid. This particular property very strongly modulates the final pH of the wine, with differences of 0.5 units between the two groups. The groups of strains with opposing behaviors, named ACIDIC and DEMALIC respectively, were compared in different musts in order to evaluate their technological and sensory impact on the wines obtained.

In the characterization of these groups of strains, targeted NMR and nontargeted LC-MS metabolomic methods were used in addition to the usual phenotypic determinations (fermentation kinetics and basic enological analysis). The ACIDIC and DEMALIC strains thus stand as a benchmark against a wide range of selected oenological strains, and are capable of providing new tools for managing the growing problems related to wine acidity in the context of climate change related to global warming.

Lachancea thermotolerans tool for natural acidification of wines

Loris Cazzanelli, Laffort Italy Srl

In response to the demands of current winemaking practice, which is increasingly looking for natural tools to manage the loss of acidity in musts and wines within the current global warming framework, Laffort research has expressed the selection of specific strains that have proven to be useful tools to address these issues from a biotechnological perspective.

In particular, a strain of Lachancea thermotolerans, isolated by mass selection within the species, has distinguished itself by presenting a marked acidifying power: in fact, it is able to transform a part of the fermentable sugars in the must into L-lactic acid, at the expense of ethanol production, thus allowing at the same time a certain decrease in alcohol content, a decisive contribution of freshness and the organoleptic rebalancing of the wines produced.

A number of innovatively selected Saccharomyces cerevisiae strains have also shown excellent evidence in managing the acid profile of musts from the very course of alcoholic fermentation, leading to wines with profiles characterized by a fresh and pleasant acidic streak, which is particularly appreciated in today’s winemaking context.

We present in the report some of the results obtained during practical winery trials.