Identification of target genes to control acetate yield during aerobic fermentation with Saccharomyces cerevisiae

Abstract

Background: Aerobic fermentation of grape must, leading to respiro-fermentative metabolism of sugars, has been proposed as way of reducing alcohol content in wines. Two factors limit the usefulness of Saccharomyces cerevisiae for this application, the Crabtree effect, and excess volatile acidity under aerobic conditions. This work aimed to explore the impact on ethanol acetate production of different S. cerevisiae strains deleted for genes previously related with the Crabtree phenotype.

Results: Recombinant strains were constructed on a wine industrial genetic background, FX10. All yeast strains, including FX10, showed respiro-fermentative metabolism in natural grape must under aerobic conditions, as well as a concomitant reduction in ethanol yield. This indicates that the Crabtree effect is not a major constrain for reaching relevant respiration levels in grape must. Indeed, only minor differences in ethanol yield were observed between the original and some of the recombinant strains. In contrast, some yeast strains showed a relevant reduction of acetic acid production. This was identified as a positive feature for the feasibility of alcohol level reduction by respiration. Reduced acetic acid production was confirmed by a thorough analysis of these and some additional deletion strains (involving genes HXK2, PYK1, REG1, PDE2 and PDC1). Some recombinant yeasts showed altered production of glycerol and pyruvate derived metabolites.

Conclusions: REG1 and PDC1 deletion strains showed a strong reduction of acetic acid yield in aerobic fermentations. Since REG1 defective strains may be obtained by non-GMO approaches, these gene modifications show good promise to help reducing ethanol content in wines.

Keywords: Aerobic fermentation; Alcohol level reduction; Carbon catabolite derepression; Crabtree effect; Volatile acidity; Wine.

Fig. 1

Simplified model showing the main role of Hxk2 and Reg1 in carbon catabolite repression (CCR). The different elements are shown in grey for the active state and empty for the inactive state. Stars on Mig1 and Hxk2 indicate a phosphorylated state. Several elements shown in the model have additional functions (either in CCR or not), and not all the factors involved in CCR are shown. Both Hxk2 and Reg1 must be active for efficient repression of many genes under CCR control Model based on [21], with additional information from [22]

Fig. 2

Growth of S. cerevisiae FX10 and different recombinant derivatives on YPgalactose. a Without 2-deoxy glucose; b supplemented with 2-deoxy glucose

Fig. 3

Principal component analysis based on the yields of main fermentation products and pyruvate derived metabolites. The PC1 and PC2 explained 64.89 and 81.97 % respectively of the total yeast strains variance under aerobic (green dots) and anaerobic (red squares) conditions

Fig. 4

Sugar consumption kinetics during anaerobic (a) and aerobic (b) fermentations of the strains indicated. Results are the average of biological triplicates Please, refer to Additional file 2: Figure S2 for SD (removed in this graph for clarity)