Innovative Microbials for Winemaking Excellence

This project sought to generate superior microbial strains and applications of these and new knowledge on fermentation management to secure and improve wine quality. The key findings are listed below. The yeast ‘Fermentome’, i.e. genes and/or processes required by yeast to sense and respond to the multiple stresses encountered during growth in grape juice to allow complete and efficient fermentation, has been further defined in this project. The High Sugar Fermentation (HSF) dataset first reported in project UA 05/01 was revisited in this study with additional genes confirmed as being necessary for fermentation completion in high sugar. This dataset was renamed the Fermentation Essential Genes (FEG) dataset and is made up of 93 genes. Two Fermentation Relevant Yeast Gene (FRYG) databases were newly compiled in this study. The first, LIT_FRYG, is a collection of genes identified in previously published studies of single stress conditions that are of relevance to fermentation. The second, SGD_FRYG, is a collection of genes associated with fermentation relevant phenotype terms reported in the Saccharomyces Genome Database. A comparison of the FEG dataset to the FRYG datasets identified eight genes not present in either the LIT_FRYG or the SGD_FRYG datasets. These genes represent unique targets for further investigation of their roles and associated biological pathways in relation to fermentation, since they have not previously been associated with any fermentation stresses. Preliminary micro scale (1.8 mL) fermentation screening of a yeast gene overexpression library has identified genes putatively involved in decreasing fermentation duration (i.e. positive regulators of fermentation). Further laboratory scale (100 mL) fermentations of candidates from the preliminary screen will be conducted as part of our future project UA 1302. Gene datasets redefined and newly developed in this study provide a valuable source of genetic information for future work in our subsequent project UA 1302. This information will be used to further understand the biological processes important for efficient and complete fermentation as well as providing targets for directed evolution of yeast strains for improved fermentation performance in oenological conditions.