A novel methodology independent of fermentation rate for assessment of the fructophilic character of wine yeast strains |
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Authors: | T?Liccioli P?J?Chambers Email author" target="_blank">V?JiranekEmail author |
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Institution: | (1) School of Agriculture, Food and Wine, The University of Adelaide, PMB 1, Glen Osmond, SA, 5064, Australia;(2) Wine Innovation Cluster, Adelaide, SA, Australia;(3) The Australian Wine Research Institute, PO Box 197, Glen Osmond, SA, 5064, Australia; |
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Abstract: | The yeast Saccharomyces cerevisiae has a fundamental role in fermenting grape juice to wine. During alcoholic fermentation its catabolic activity converts sugars
(which in grape juice are a near equal ratio of glucose and fructose) and other grape compounds into ethanol, carbon dioxide
and sensorily important metabolites. However, S. cerevisiae typically utilises glucose and fructose with different efficiency: glucose is preferred and is consumed at a higher rate
than fructose. This results in an increasing difference between the concentrations of glucose and fructose during fermentation.
In this study 20 commercially available strains were investigated to determine their relative abilities to utilise glucose
and fructose. Parameters measured included fermentation duration and the kinetics of utilisation of fructose when supplied
as sole carbon source or in an equimolar mix with glucose. The data were then analysed using mathematical calculations in
an effort to identify fermentation attributes which were indicative of overall fructose utilisation and fermentation performance.
Fermentation durations ranged from 74.6 to over 150 h, with clear differences in the degree to which glucose utilisation was
preferential. Given this variability we sought to gain a more holistic indication of strain performance that was independent
of fermentation rate and therefore utilized the area under the curve (AUC) of fermentation of individual or combined sugars.
In this way it was possible to rank the 20 strains for their ability to consume fructose relative to glucose. Moreover, it
was shown that fermentations performed in media containing fructose as sole carbon source did not predict the fructophilicity
of strains in wine-like conditions (equimolar mixture of glucose and fructose). This work provides important information for
programs which seek to generate strains that are faster or more reliable fermenters. |
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