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Appl. Environ. Microbiol., 02 1995, 461-467, Vol 61, No. 2
V Jiranek, P Langridge and PA Henschke
Saccharomyces cerevisiae wine-producing yeast cultures grown under model
winemaking conditions could be induced to liberate hydrogen sulfide (H2S)
by starvation for assimilable nitrogen. The amount of H2S produced was
dependent on the yeast strain, the sulfur precursor compound, the culture
growth rate, and the activity of the sulfite reductase enzyme (EC 1.8.1.2)
immediately before nitrogen depletion. Increased H2S formation relative to
its utilization by metabolism was not a consequence of a de novo synthesis
of sulfite reductase. The greatest amount of H2S was produced when nitrogen
became depleted during the exponential phase of growth or during growth on
amino acids capable of supporting short doubling times. Both sulfate and
sulfite were able to act as substrates for the generation of H2S in the
absence of assimilable nitrogen; however, sulfate reduction was tightly
regulated, leading to limited H2S liberation, whereas sulfite reduction
appeared to be uncontrolled. In addition to ammonium, most amino acids were
able to suppress the liberation of excess H2S when added as sole sources of
nitrogen, particularly for one of the strains studied. Cysteine was the
most notable exception, inducing the liberation of H2S at levels exceeding
that of the nitrogen-depleted control. Threonine and proline also proved to
be poor substitutes for ammonium. These data suggest that any compound that
can efficiently generate sulfide-binding nitrogenous precursors of organic
sulfur compounds will prevent the liberation of excess H2S.
Copyright © 1995, American Society for Microbiology
Regulation of hydrogen sulfide liberation in wine-producing Saccharomyces cerevisiae strains by assimilable nitrogen
Australian Wine Research Institute, Glen Osmond.
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