Location: Horticultural Crops Research
Project Number: 2072-22000-043-03-G
Project Type: Grant
Start Date: Sep 11, 2014
End Date: Sep 30, 2018
1. Determine levels of sulfite and hydrogen sulfide produced during model grape juice fermentation by a limited number of sulfite-producing commercial wine yeast strains as a function of time, temperature, and available nitrogen. 2. In the above yeast strains, determine DNA sequences that control expression of the SSU1 gene encoding the native yeast sulfite efflux pump responsible for excretion of sulfite into wine.
Standard procedures will be employed to make small lots of wine or model wines using presumptive sulfite-producing commercial wine yeast strains. Strains under consideration include, but are not limited to Lalvin BM45, Lalvin ICV OKAY, Lalvin EC1118, Uvaferm WAM, Lalvin ICV Opale, and Lalvin K1 V1116. Sulfite and hydrogen sulfide will be measured over the course of the fermentations by standard methods. Student’s 2-tailed T test or the Wilcoxon–Mann-Whitney 2-tailed test will be used to assess the statistical significance of any differences observed in sulfite or hydrogen sulfide levels. In order to determine the DNA sequences that control expression of the SSU1 gene in the tested strains, DNA will be extracted and PCR and inverse PCR will be performed as described. Control or “promoter” sequences will be identified by comparison to the public Saccharomyces cerevisiae genome database (http://www.yeastgenome.org). Correlations between sulfite production and SSU1 promoter sequences will be sought as an initial step in rationalizing sulfite levels in wine. Amendment #3 adds funds to continue the current research objectives and will be used to retest promising strains and to assess the possibility of reducing sulfite levels.