High capacity xylose transport in Candida intermedia PYCC 4715.
Xylose-utilising yeasts were screened to identify strains with high xylose transport capacity. Among the fastest-growing strains in xylose medium, Candida intermedia PYCC 4715 showed the highest xylose transport capacity. Maximal specific growth rate was the same in glucose and xylose media (mu(max)=0.5 h-1, 30 degrees C). Xylose transport showed biphasic kinetics when cells were grown in either xylose- or glucose-limited culture. The high-affinity xylose/proton symport system (Km = 0.2 mM, Vmax = 7.5 mmol h-1 g-1) was more repressed by glucose than by xylose. The less specific low-affinity transport system (K = 50 mM, Vmax = 11 mmol h-1 g-1) appeared to operate through a facilitated-diffusion mechanism and was expressed constitutively. Inhibition experiments showed that glucose is a substrate of both xylose transport systems.
Gárdonyi
Márk
M
Centro de Recursos Microbiológicos (CREM), Faculty of Sciences and Technology, New University of Lisbon, 2829-516, Caparica, Portugal.
Osterberg
Måns
M
Rodrigues
Carla
C
Spencer-Martins
Isabel
I
Hahn-Hägerdal
Bärbel
B
D001693:Biological Transport, Active; D002175:Candida / Q000378:metabolism*; D003470:Culture Media; D005285:Fermentation; D005947:Glucose / Q000378:metabolism; D007700:Kinetics; D014994:Xylose / Q000378:metabolism*
D003470:Culture Media; D014994:Xylose; D005947:Glucose