Australasian Biotechnology,
Volume 7 Number 3, May/June 1997, pp.149-154
The importance of stress tolerance to baker's yeast
Code Number: AU97021
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Baker's yeasts are mostly strains of Saccharomyces cerevisiae.
They are able to reproduce rapidly by aerobic metabolism, which is
important to their economic efficiency for producers. They are also capable
of vigorous fermentation (ie., carbon dioxide and ethanol production
via glycolytic catabolism of sugars) in a variety of doughs and bread
manufacturing processes, which is essential for their usefulness in the
baking industry. In reality, baker's yeast never see ideal physiological
conditions and are subjected to numerous stresses including, nutritional
starvation, osmotic pressure, oxidation, temperature abuse, and in some
cases dehydration/rehydration or freezing and thawing. Nevertheless, in
order for a yeast strain to be of industrial use it must be able to adapt
to unfavourable environments and to produce the necessary growth and
fermentation rates. The baker's yeast industry is very competitive and the
production of new strains better able to cope with the varieties of
stresses encountered during growth and application is of paramount
importance to manufacturers. The ease of genetic manipulation of yeast
(both by classical and recombinant means) and our knowledge of the DNA
sequence of S. cerevisiae, would suggest that it is easy to generate
new strains with markedly improved economic performance. However, such
improvements remain limited by our understanding of key physiological
processes that determine commercially relevant traits. Thus there is a need
for continued effort in fundamental research into key biological causes and
effects of economically relevant traits. Indeed an improved understanding
of the biological consequences of stresses and of the nature of stress
response in yeast is an essential prerequisite to enhancing strains for the
baking industry, and is arguably rate limiting in producing major advances
in strain improvement.
Copyright 1997 Australian Biotechnology Association Ltd.