Monitoring the spreading of commercial wine yeasts in the vineyards
Van Rensburg, P
University of Stellenbosch. Faculty of AgriSciences. Institute for Wine Biotechnology
Lambrechts, M G
Muller, C A
– To determine the amount of commercial wine yeasts present in nature.
– To establish a knowledge base on the survival rate and spreading capabilities of commercial wine yeasts in nature.
– To determine how commercial wine yeasts found on grapes influence fermentations in the cellar if they occur in high cell concentrations on grapes.
– To use this knowledge to predict the possible spreading of recombinant wine yeasts in nature and how they will influence fermentations in the cellar.
The yeast Saccharomyces cerevisiae is an important factor contributing to the quality of wines and is therefore one of our main research areas. Apart from classical yeast studies (breeding), a tremendous amount of research is dependent on recombinant DNA techniques (genetic engineering) to enable wine yeasts to produce heterologous enzymes (pectinases, glucanases, xylanases, ß-glucosidases, etc.), degrade polysaccharides and malic acid, increase glycerol production and secrete antimicrobial peptides (bacteriocins). The release of recombinant yeast strains (genetically modified organisms, GMOs) is subject to statutory approval. Some of the important questions that need answering include: will a recombinant wine yeast be able to multiply and spread in nature, and will this GMO be able to out compete the natural microflora because of its newly acquired genetic trait. Since the existing commercial wine yeasts will be used for these manipulations, it is absolutely essential to know to what extent these existing commercial wine yeast strains survive and spread in nature and to what extent they influence the fermentations of the following year. With the recent release of NT116 and NT50 we have an excellent opportunity to follow the spreading of these yeasts.