engleski

Evolution of Saccharomyces paradoxus strain RO88 forbiological deacidification of wine

To produce a high-quality wine, it is important to obtain a fine balance between the various chemical ingredients. This is more of a challenge in wines that have a high acidity due to excess malic acid, since wine yeast is general cannot effectively degrade malic acid during fermentation. An indigenous Saccharomyces paradoxus strain RO88 was able to degrade 26 and 28% of the malic acid present in synthetic grape must containing 0, 3% and 0, 8% malic acid. In Chardonnay must the S.paradoxus strain degraded 38% of the malic acid present in the must and was able to produce a wine of good quality, whereas Schizosaccharomyces pombe strain F was very effective in the removal of malic acid, but did not produce a wine of high quality. The expression of the malic enzyme gene (MAE1) of S.paradoxus RO88, S.bayanus EC1118 and S.cerevisiae 71B were compared to elucidate the difference in malic acid degradation. The regulation of the malic enzyme gene of S.paradoxus differs from that of the other wine yeasts: transcription of the gene increased in response to a higher glucose concentration, as well as towards the end of fermentation. Significant DNA sequence differences were identified in the S.paradoxus RO88 MAE1 promoter region when compared to that of S.bayanus EC1118 and S.cerevisiae 71B. We have shown that S.paradoxus strain RO88 is able to effectively degrade malic acid in both synthetic grape and Chardonnay must. This strain was able to produce a wine of good quality and may proof to be of value for biological deacidification of wines. The mechanism and proteins involved in the degradation of malic acid is yet unknown, nut our results suggest that the malic enzyme may ply an important role to enable the yeast to respond to different conditions. As was previously demonstrated for the S.pombe malic enzyme, the S.paradoxus malic enzyme gene seems to respond to the glucose concentration rather than to the residual malic acid concentration.

malic acid; Saccharomyces paradoxus; wine

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