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L-Arabinose metabolism in Candida arabinofermentans PYCC 5603T and Pichia guilliermondii PYCC 3012: influence of sugar and oxygen on product formation.

Fonseca C, Spencer-Martins I, Hahn-Hägerdal B

Centro de Recursos Microbiológicos (CREM), Faculty of Sciences and Technology, New University of Lisbon, 2829-516, Caparica, Portugal.

L-Arabinose utilization by the yeasts Candida arabinofermentans PYCC 5603(T) and Pichia guilliermondii PYCC 3012 was investigated in aerobic batch cultures and compared, under similar conditions, to D-glucose and D-xylose metabolism. At high aeration levels, only biomass was formed from all the three sugars. When oxygen became limited, ethanol was produced from D-glucose, demonstrating a fermentative pathway in these yeasts. However, pentoses were essentially respired and, under oxygen limitation, the respective polyols accumulated--arabitol from L-arabinose and xylitol from D-xylose. Different L-arabinose concentrations and oxygen conditions were tested to better understand L-arabinose metabolism. P. guilliermondii PYCC 3012 excreted considerably more arabitol from L-arabinose (and also xylitol from D-xylose) than C. arabinofermentans PYCC 5603(T). In contrast to the latter, P. guilliermondii PYCC 3012 did not produce any traces of ethanol in complex L-arabinose (80 g/l) medium under oxygen-limited conditions. Neither sustained growth nor active metabolism was observed under anaerobiosis. This study demonstrates, for the first time, the oxygen dependence of metabolite and product formation in L-arabinose-assimilating yeasts.

Published 4 June 2007 in Appl Microbiol Biotechnol, 75(2): 303-10.
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