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Appl. Environ. Microbiol., Apr 1995, 1420-1425, Vol 61, No. 4
EM Lohmeier-Vogel, B Hahn-Hagerdal and HJ Vogel
Candida tropicalis can ferment both hexose and pentose sugars. Here, we
have used 31P and 13C nuclear magnetic resonance spectroscopy to study the
capacity of this yeast species to metabolize glucose or xylose when
immobilized in small (< 1-mm-diameter) agarose beads. Immobilized C.
tropicalis metabolizing glucose showed rapid initial growth within the
beads. A corresponding drop in the intracellular pH (from 7.8 to 7.25) and
hydrolysis of intracellular polyphosphate stores were observed. Although
the initial rate of glucose metabolism with immobilized C. tropicalis was
similar to the rate observed previously in cell suspensions, a decrease by
a factor of 2.5 occurred over 24 h. In addition to ethanol, a significant
amount of glycerol was also produced. When immobilized C. tropicalis
consumed xylose, cell growth within the beads was minimal. The
intracellular pH dropped rapidly by 1.05 pH units to 6.4. Intracellular ATP
levels were lower and intracellular Pi levels were higher than observed
with glucose-perfused cells. Consumption of xylose by immobilized C.
tropicalis was slower than was previously observed for oxygen-limited cell
suspensions, and xylitol was the only fermentation product.
Copyright © 1995, American Society for Microbiology
Phosphorus-31 and carbon-13 nuclear magnetic resonance study of glucose and xylose metabolism in agarose-immobilized Candida tropicalis
Department of Biological Sciences, University of Calgary, Alberta, Canada.
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