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

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.