Ethanol production from wheat straw hemicellulose hydrolysate by Pichia stipitis

Ethanol production was evaluated from wheat straw (WS) hemicellulose acid h ydrolysate using an adapted and parent strain of Pichia stipitis. NRRL Y-71 24. The treatment by boiling and overliming with Ca(OH)(2) significantly im proved the fermentability of the hydrolysate. Ethanol yield (Y-p,Y-s) and p roductivity (Q(p) av) were increased 2.4 +/- 0.10 and 5.7 +/- 0.24 folds, r espectively, compared to neutralized hydrolysate. Adaptation of the yeast t o the hydrolysate resulted further improvement in yield and productivity. T he maximum yield was 0.41 +/- 0.01 g(p) g(s)(-1), equivalent to 80.4 +/- 0. 55% theoretical conversion efficiency. Acetic acid, furfurals and lignins p resent in the hydrolysate were inhibitory to microbial growth and ethanol p roduction. The addition of these inhibitory components individually or in v arious combinations at a concentrations similar to that found in hydrolysat e to simulated medium resulted a reduction in ethanol yield (Y-p,Y-s) and p roductivity (Q(p) av). The hydrolysate used had the following composition ( expressed in g l(-1)): xylose 12.8 +/- 0.25; glucose 1.7 +/- 0.3; arabinose 2.6 +/- 0.21 and acetic acid 2.7 +/- 0.33. (C) 2001 Elsevier Science B.V. All rights reserved.