Genetically modified wine yeasts and risk assessment studies covering different steps within the wine making process

The use of gene technology to modify the genome of wine yeasts belonging to the species Saccharomyces cerevisiae began in the early 1990s. From a purely scientific point of view, many yeast constructs [genetically modified organisms (GMO)] have been made so far, covering more or less all stages of the wine making process in which microorganisms or commercial enzymes play a key role. The range of theoretical applications is summarised in this report. So far, only two wine-producing countries worldwide allow the use of engineered wine yeasts; the changing situation in Germany regarding consumers’ attitudes towards gene technology, and foodstuffs thus produced, will be outlined here. Experiments at the Geisenheim Research Center have highlighted the essential stages of the wine making process where yeasts are involved by using engineered wine yeasts in comparison with non-engineered yeast strains. Greenhouse simulations revealed the persistence of genetically modified (gm) yeasts when these were used as fertilizers, as vintners do with yeast lees after the fermentation process. Furthermore, the persistence of engineered yeast was also monitored in fermentations, after bottling, and after biological treatment of winery waste water. It turned out that engineered wine yeast strains behave like non-engineered wine yeasts. They also persist in the winery interior and installations as well as becoming part of the yeast flora on grape vines in a vineyard with annual fluctuations in the composition of the yeast populations.