Evaluation of Gene Modification Strategies for the Development of Low-Alcohol-Wine Yeasts

Abstract

<jats:title>ABSTRACT</jats:title><jats:p><jats:named-content content-type="genus-species">Saccharomyces cerevisiae</jats:named-content>has evolved a highly efficient strategy for energy generation which maximizes ATP energy production from sugar. This adaptation enables efficient energy generation under anaerobic conditions and limits competition from other microorganisms by producing toxic metabolites, such as ethanol and CO<jats:sub>2</jats:sub>. Yeast fermentative and flavor capacity forms the biotechnological basis of a wide range of alcohol-containing beverages. Largely as a result of consumer demand for improved flavor, the alcohol content of some beverages like wine has increased. However, a global trend has recently emerged toward lowering the ethanol content of alcoholic beverages. One option for decreasing ethanol concentration is to use yeast strains able to divert some carbon away from ethanol production. In the case of wine, we have generated and evaluated a large number of gene modifications that were predicted, or known, to impact ethanol formation. Using the same yeast genetic background, 41 modifications were assessed. Enhancing glycerol production by increasing expression of the glyceraldehyde-3-phosphate dehydrogenase gene,<jats:italic>GPD1</jats:italic>, was the most efficient strategy to lower ethanol concentration. However, additional modifications were needed to avoid negatively affecting wine quality. Two strains carrying several stable, chromosomally integrated modifications showed significantly lower ethanol production in fermenting grape juice. Strain AWRI2531 was able to decrease ethanol concentrations from 15.6% (vol/vol) to 13.2% (vol/vol), whereas AWRI2532 lowered ethanol content from 15.6% (vol/vol) to 12% (vol/vol) in both Chardonnay and Cabernet Sauvignon juices. Both strains, however, produced high concentrations of acetaldehyde and acetoin, which negatively affect wine flavor. Further modifications of these strains allowed reduction of these metabolites.</jats:p>

Reduction of Ethanol Yield and Improvement of Glycerol Formation by Adaptive Evolution of the Wine Yeast Saccharomyces cerevisiae under Hyperosmotic Conditions

“…Indeed, there have been many efforts to develop engineered wine yeast strains with reduced ethanol yield (6,8). One of the most efficient approaches was to divert metabolism toward increased production of glycerol and thus away from ethanol (9,10). In Saccharomyces cerevisiae, glycerol plays major roles in redox homeostasis and in osmotic stress resistance: it is the main compatible solute in yeast (11).…”

Viticultural and Biotechnological Strategies to Reduce Alcohol Content in Red Wines

“…On the other hand, an atractive option would be to develop engineered wine yeast with reduced ethanol yield. So far, one of the most promising strategies is to redirect the metabolic lux toward an increased production of glycerol instead ethanol [2,35]. However, this strategy has shown some unwanted efects like an overproduction of undesirable compounds from an organoleptic point of view [1].…”

Synthetic genome engineering forging new frontiers for wine yeast

“…To date, using genetic engineering [20,43,44] and non-GM techniques, [45] such as classical breeding (hybridization), adaptive laboratory evolution, and mutagenesis, several non-GM and GM wine strains have been developed with increased robustness, fermentation performance, health-related properties, and/or sensory attributes. Examples include strains that produce wines with lower alcohol levels; [46][47][48][49][50][51][52][53][54][55] mutants that limit the production of unwanted hydrogen-sulfide off-flavors and volatile acidy; [56][57][58] and strains that produce desirable esters, [59,60] terpenes, [61] and thiols ( Figure 18). [62][63][64][65][66][67][68][69][70] Efforts are also underway to express the a-guaiene-2-oxidase from grapevine in S. cerevisiae, thereby equipping wine yeast to transform grapederived a-guaiene to the sought-after spicy aroma compound of Shiraz wine, rotundone.…”