Influence of cultivation conditions on xylose-to-xylitol bioconversion by a new isolate of Debaryomyces hansenii

About 270 yeast isolates were screened for xylitol production using xylose as the sole carbon source. The best isolate, Debaryomyces hansenii UFV-170, released 5.84 g L-1 xylitol from 10 g L-1 xylose after 24 h, corresponding to a yield of xylitol on consumed substrate (Y-P/S) of 0.54 g g(-1). This strain was cultivated batch-wise at variable starting concentrations of xylose (S-o) and biomass (X-o) and agitation intensity, in order to improve xylitol production and to evaluate, through simple carbon balances, the influence of these conditions on xylose metabolism. Under the best microaerobic conditions (So = 53 g L-1 X-o = 1.4 g L-1, 200 rpm), xylitol production reached 37.0 g L-1, corresponding to xylitol volumetric productivity of 1.0 g L-1 h(-1), specific productivity of 0.22 g g(-1) h(-1) and YP/s = 0.76 g g(-1). Almost 83% of xylose was consumed for xylitol production, the rest being consumed for growth, while respiration was negligible. The new isolate appeared to be a promising alternative for industrial xylitol bioproduction. (c) 2007 Elsevier Ltd. All rights reserved.