The impact of Torulaspora delbrueckii has been investigated for the first time in the production of Amarone wine, a high-alcohol dry red wine obtained from withered grapes. In two different vinifications, winery trials were inoculated by a selected strain of T. delbrueckii simultaneously and/or sequentially to Saccharomyces cerevisiae. Implantation analysis demonstrated T. delbrueckii was able to rapidly colonise the must remaining in wine up to 16.5 % v v -1 of ethanol. The effects of T. delbrueckii on the aroma of Amarone wine were linked to its persistence during the fermentation and a great number of compounds varied in wine obtained with mixed cultures. The most significant changes were observed among alcohols, fermentative esters, fatty acids and lactones, which are important in the Amarone wine flavour. This study confirms the role of T. delbrueckii on wine aroma and the potential of non-Saccharomyces use in winemaking.

The SNF3 protein, Snf3p, of Saccharomyces cerevisiae was initially thought to be a high affinity glucose transporter required for efficient catabolism of low glucose concentrations. We now report evidence suggesting that Snf3p is a regulatory protein and not a catabolic transporter. The C‐terminal domain of Snf3p is able to complement the growth defect on solid media of snf3 null mutants independent of attachment to the membrane‐spanning domains. However, the C‐terminal domain is unable to fully restore high affinity glucose transport to a snf3 null strain. Examination of deletions of the C‐terminal domain of intact SNF3 demonstrates that this region is required for both the growth and transport functions of Snf3p. Loss of the SNF3 gene leads to a long‐term adaptation phenotype for cells grown in liquid medium at low substrate concentrations in the presence of the respiratory inhibitor, antimycin A. The presence of the C‐terminal domain shortens the time required for adaptation in a snf3 null strain. Thus, Snf3p appears to affect ability to adapt to low substrate conditions, but does not confer an absolute defect in uptake of substrate. Taken together, these data suggest that Snf3p is a regulatory protein likely functioning in the detection of glucose. © 1997 by John Wiley & Sons, Ltd.

The purpose of this work was to study the induction of malolactic fermentation (MLF) in a wine that does not often support malic acid deacidification because of its high alcohol content. Amarone wine, known for its high alcohol content, served as a model. Simultaneous and sequential alcoholic and malolactic fermentation (AF/MLF) were conducted by direct inoculation of bacteria, which resulted in successful MLF in wines containing approximately 16% (v/v) alcohol. At higher ethanol contents, stuck MLF occurred because of growth inhibition. To overcome this technological problem, the performance of bacteria was tested in wine containing approximately 17% (v/v) ethanol using a starter preparation consisting of cells acclimatised in a wine-water solution (1:1) for 24 h and 48 h respectively. Total l-malic acid depletion was recorded when the bacterial cells that had been acclimatised for 48 h were inoculated simultaneously with yeast to conduct AF. The method by which the bacterial cultures are prepared and the time of inoculation affects the efficacy of MLF in high-alcohol wines. The inoculation of yeasts with acclimatised bacteria before AF seems to be a valid strategy to obtain complete MLF in high-alcohol wines. Malolactic fermentation (MLF) in wine is characterised by the conversion of l-malic acid to L-lactic acid and carbon dioxide, and subsequent changes in aroma and taste profiles. This secondary fermentation is usually conducted by Oenococcus oeni (Lonvaud-Funel, 1999). MLF may occur spontaneously or may be induced by the inoculation of selected bacterial cultures that are commercially available as pure freeze-dried cultures. These strains tolerate high alcohol (> 13.0%, v/v) and low pH (< 3.20), traits which allow them to grow and survive in harsh environments such as wine. These two parameters, in combination with the presence of SO 2 , low temperature and scarce nutrients, contribute to diminish the success of biological deacidification (Ribéreau-Gayon et al., 2006). The ethanol content in wine plays a critical role in MLF, as it disrupts membrane structures and affects many membrane-associated processes, including those involved in stress resistance and malolactic activity (Da Silveira et al., 2003, Chu-Ky et al., 2005).

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