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Appl. Environ. Microbiol., Jan 1997, 145-150, Vol 63, No. 1
DK Myers, DT Lawlor and PV Attfield
In the past, the fermentation activity of Saccharomyces cerevisiae in
substrates with a high concentration of sucrose (HSuc), such as sweet bread
doughs, has been linked inversely to invertase activity of yeast strains.
The present work defines the limits of the relationship between invertase
activity and fermentation in hyperosmotic HSuc medium. Fourteen polyploid,
wild-type strains of S. cerevisiae with different invertase levels gave a
similar ranking of fermentation activity in HSuc and in medium in which
glucose and fructose replaced sucrose (HGF medium). Thus, invertase is
unlikely to be the most important determinant of fermentation in sweet
doughs. Yeasts produce the compatible solute-osmoprotective compound
glycerol when exposed to hyperosmotic environments. Under low sugar
concentrations (and nonstressing osmotic pressure), there was no
correlation between glycerol and fermentation activities. However, there
was a strong correlation between the ability of yeasts to ferment in HSuc
or HGF medium and their capacity to produce and retain glycerol
intracellularly. There was also a strong correlation between intracellular
glycerol and fermentation activity of yeasts in a medium in which the
nonfermentable sugar alcohol sorbitol replaced most of the sugars (HSor),
but the ability to produce and retain glycerol was greater when yeasts were
incubated in HGF medium under the same osmotic pressure. The difference
between the amounts of glycerol produced and retained in HSor and in HGF
media varied with strains. This implies that high fermentable sugar
concentrations cause physiological conditions that allow for enhanced
glycerol production and retention, the degree of which is strain dependent.
In conclusion, one important prerequisite for yeast strains to ferment
media with high concentrations of sugar is the ability to synthesize
glycerol and especially to retain it.
Copyright © 1997, American Society for Microbiology
Influence of invertase activity and glycerol synthesis and retention on fermentation of media with a high sugar concentration by Saccharomyces cerevisiae
Yeast Physiology Research Group, Burns Philp Technology and Research Centre, North Ryde, New South Wales, Australia.
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