Is Saccharomyces cerevisiae suitable for winemaking under aerobic conditions?

Trabajo presentado en el 3rd Iberoamerican Congress on Biotechnology, celebrado en Braga (Portugal), del 7 al 9 de abril de 2022

The increasing ethanol content in wine, due both climate change and market trends, has been a matter of concern for winemaking industry for the last two decades. The use of yeast respiratory metabolism has been proposed as a promising approach to solve this problem. Contrary to initial expectation, the use of S. cerevisiae for this purpose is not hampered because Crabtree effect -causing low respiration rates- but by acetic acid overproduction generated under the necessary aerobic conditions. In this work, we performed a screening of 25 S. cerevisiae oenological strains, with the aim to identify suitable strains for aerobic fermentation, and the optimization of their fermentation conditions to obtain a reduced ethanol yield with an acceptable volatile acidity (1). The data showed a low variability in ethanol yield but a great diversity in acetic acid yield. Some strains with very low volatile acidity under aerobic conditions were identified. The three more promising strains were selected for further characterization in bioreactor under both aerobic and anaerobic conditions, compared with a regular oenological strain. As expected, the ethanol yield of all the strains was lower under aerobic than anaerobic conditions. Two of the strains showed low acetic acid production under aerobic conditions. The volatile profile analysis showed differences strain-dependent and aeration conditions-dependent. The aeration process was optimized in laboratory bioreactors for the most promising strain. Even for this low acetate producer strain, the transition from aerobic to anaerobic fermentation triggers acetic acid production. A gradual decrease of aeration allowed a significant ethanol reduction with an acceptable volatile acidity (1).

This work was funded by the Spanish Government through grants AGL 2015-63629-R (co-financed by FEDER funds), PCI 2018-092949 (funded by MCIN/AEI /10.13039/501100011033 and the European Union). JT is funded by FGCSIC by the COMFUTURO program. AMG predoctoral contract is funded by Consejería de Desarrollo Económico e Innovación de la C.A de La Rioja, EC was recipient of JAE-Intro fellowship from the Spanish National Research Council (CSIC).