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Applied and Environmental Microbiology, August 1999, p. 3594-3598, Vol. 65, No. 8
Departamento de Biologia, Centro de
Ciências do Ambiente, Universidade do Minho, 4709 Braga
Codex, Portugal
Received 13 January 1999/Accepted 20 May 1999
Debaryomyces hansenii is a yeast species that is known
for its halotolerance. This organism has seldom been mentioned as a pentose consumer. In the present work, a strain of this species was
investigated with respect to the utilization of pentoses and hexoses in
mixtures and as single carbon sources. Growth parameters were
calculated for batch aerobic cultures containing pentoses, hexoses, and
mixtures of both types of sugars. Growth on pentoses was slower than
growth on hexoses, but the values obtained for biomass yields were very
similar with the two types of sugars. Furthermore, when mixtures of two
sugars were used, a preference for one carbon source did not inhibit
consumption of the other. Glucose and xylose were transported by cells
grown on glucose via a specific low-affinity facilitated diffusion
system. Cells derepressed by growth on xylose had two distinct
high-affinity transport systems for glucose and xylose. The sensitivity
of labeled glucose and xylose transport to dissipation of the
transmembrane proton gradient by the protonophore carbonyl cyanide
m-chlorophenylhydrazone allowed us to consider these
transport systems as proton symports, although the cells displayed
sugar-associated proton uptake exclusively in the presence of NaCl or
KCl. When the Vmax values of transport systems
for glucose and xylose were compared with glucose- and xylose-specific
consumption rates during growth on either sugar, it appeared that
transport did not limit the growth rate.
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Transport and Utilization of Hexoses and Pentoses
in the Halotolerant Yeast Debaryomyces hansenii
*
Corresponding author. Mailing address: Departamento de
Biologia, Universidade do Minho, Campus de Gualtar, 4709 Braga Codex, Portugal. Phone: 351-53-604313/11/10. Fax: 351-53-678980. E-mail: clucas{at}bio.uminho.pt.
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