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Appl. Environ. Microbiol., 04 1995, 1414-1419, Vol 61, No. 4
EM Lohmeier-Vogel, B Hahn-Hagerdal and HJ Vogel
The metabolism of glucose and xylose was studied as a function of
oxygenation in suspensions of Candida tropicalis by 31P and 13C nuclear
magnetic resonance spectroscopy. Both the rate of carbohydrate metabolism
and the cytoplasmic pH were independent of the rate of oxygenation in cells
metabolizing glucose. However, these two parameters were markedly dependent
on the rate of oxygenation in C. tropicalis cells metabolizing xylose. For
example, the cytoplasmic pH in fully oxygenated xylose-metabolizing cells
was 7.8 but decreased to 6.3 in anoxic cells. In general, suspensions of
cells consuming xylose had a lower rate of sugar uptake, a more acidic
cytoplasmic pH, lower levels of sugarphosphomonoesters (SP) and ATP, higher
levels of intracellular Pi, a more alkaline vacuolar pH, and a lower rate
of extracellular Pi assimilation and polyphosphate synthesis than cells
consuming glucose. These observations indicate that C. tropicalis
metabolizing xylose is less energized than glucose-metabolizing cells. On
both carbon sources, however, an inverse correlation between intracellular
levels of SP and Pi was observed. Also, uptake of extracellular Pi
correlated with the synthesis of polyphosphates within the cells. During
anoxia, Pi was not taken up, and polyphosphates were hydrolyzed instead to
fulfill the cells' requirements for phosphate.
Copyright © 1995, American Society for Microbiology
Phosphorus-31 and carbon-13 nuclear magnetic resonance studies of glucose and xylose metabolism in Candida tropicalis cell suspensions
Department of Biological Sciences, University of Calgary, Alberta, Canada.
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