Presenter: Graham G. Stewart, GGStewart Associates, Cardiff,
U.K.
Brewer’s yeast strains (both lager and ale cultures) belong
to a commercially significant grouping of yeast species that
are used for the production of food, alcoholic beverages,
and drugs for medicinal purposes. In addition, this yeast
group is an invaluable model eukaryote because it is a single
cell that can be genetically manipulated and cultured in the
laboratory. The fact that it possesses a cell structure similar
to plants and animals, including humans, that includes cell
walls, a nucleus, vacuole(s), membranes, and mitochondria is
also very important. In Saccharomyces cerevisiae and related
species (including brewer’s yeast strains) the most frequent
spontaneous mutation is to the specific DNA contained in its
mitochondria (mtDNA). This mutation is termed respiratory
deficiency (RD) or petite because of the small size of the
resulting colonies compared with the respiratory sufficient
variant. The phenotypic effects of the RD mutation in a
brewer’s yeast culture are profound, and examples, particularly
during wort fermentation, will be discussed. In addition,
fundamental research on yeast mtDNA has assisted our
knowledge of human mitochondrial function and disease.
There is a group of diseases caused by dysfunctional mtDNA
often as a result of mutation of mtDNA. These diseases include
type one diabetes, deafness, hereditary optic neuropathy, and
epilepsy, to name just a few. Mitochondrial research with yeast
has provided considerable information and assisted medical
research on many of the diseases listed above. Indeed, current
research removing the mtDNA from the ovaries of a diseased
patient and replacing it with unmutated mtDNA from a donor
to produce healthy zygotes is a novel technique with significant
potential. Importantly, in the context of this presentation,
without mitochondrial research on brewer’s yeast and its
close relatives, these medical developments would have been
inhibited, impeded, and protracted.
Graham Stewart, emeritus professor in brewing and distilling
at Heriot-Watt University, Edinburgh, Scotland, was director
and professor of the International Centre for Brewing and
Distilling, Heriot-Watt University, from 1994 to 2007. He
received his BS. (Honors) degree in microbiology and
biochemistry from the University of Wales, Cardiff, and Ph.D.
and D.S. degrees from Bath University. He was a lecturer in
biochemistry in the School of Pharmacy at Portsmouth College
of Technology (now Portsmouth University) from 1967 to 1969.
From 1969 to 1994 he held a number of technical positions
with Labatt’s in Canada and from 1986 to 1994 was its brewing
technical director. He was president of the Institute of Brewing
(now the Institute of Brewing and Distilling) in 1999 and 2000.
He is also a member of MBAA and ASBC. He holds fellowships
in IBD, the Institute of Biology, and the American Academy
of Microbiology. He has more than 300 publications (books,
patents, review papers, articles, and peer-reviewed papers) to
his name. Upon retiring he established a consulting company,
GGStewart Associates, with an office in Cardiff, Wales. He
was awarded the IBD Horace Brown Medal in 2008, the ASBC
Award of Excellence in 2008, the MBAA Presidential Award in
1983 and 1998, the MBAA Award of Distinction in 2009, and
the Society of Industrial Microbiology Charles Thom Award in
1988.
View Presentation
