Marion Favier, Ana Hranilovic, Margaux Bernard, Maitena Muro, Philippe Marullo, Karine Gay, Chantal Mansour, and Joana Coulon*
*Biolaffort, 11 Rue Aristide Bergès, 33270 Floirac, Floirac, France (joana.coulon@laffort.com)

During the past decades, drastic changes in grape must composition have occurred, leading to wines with higher ethanol content and lower acidity (Van Leeuwen et al. 2019). Both linked to climate change, these two features can be addressed concurrently using innovative techniques for microbial selection.

Many efforts focused on non-Saccharomyces yeast selection to lower the ethanol/sugars ratio during alcoholic fermentation. Lachancea thermotolerans is one of the most interesting species because it partially routes glucose and fructose to L-lactic acid, de facto lowering ethanol production during alcoholic fermentation while also acidifying the wines. Previous studies highlighted the importance of strain selection, as not all strains are alike (Hranilovic et al. 2018), leading to the selection of one strain, Zymaflore Omega. Further assays also showed that the enological environment and inoculation scenario drastically influence lactic acid production, as described here.

This strain must be associated with a Saccharomyces cerevisiae strain to complete alcoholic fermentation. Our latest selection program delivered a strain concentrating most genetic elements linked to malic acid preservation/production and lower ethanol/sugars yield, named Zymaflore Klima. The L-malic acid production of this strain depends on the initial malic acid content but can lead to 0.5 to 1 g/L produced in low-malic acid musts, while losing 0.2 to 0.3% vol ethanol.

Malolactic fermentation leads to decreases in acidity due to transformation of L-malic acid into L-lactic acid. However, this can be tempered using an Oenococcus oeni strain selected for low citric acid consumption, named Lactoenos Berry. Considering several assays, results show that titratable acidity can gain 0.5 g/L as tartaric equivalents compared to indigenous strains.

Together, these three carefully selected microorganisms lowered ethanol by 0.5% vol and increased TA by up to 2 g/L.

Funding Support: Biolaffort