Ethanol production from hardwood spent sulfite liquor using an adapted strain of Pichia stipitis

Conditions have been optimized for fermentation of pretreated hardwood spen t sulfite liquor (HSSL) using an adapted strain of Pichia stipitis, The pre treatments, consisting of boiling and overliming with Ca(OH)(2) of HSSL, to partially remove inhibitors, and adaptation of the yeast strain to HSSL, w ere both critical for a successful fermentation. Ethanol concentration was Increased from 6.7 to 20.2 g l(-1) using adapted P. stipitis (A) and pretre ated HSSL. The maximum ethanol yield (Y-p/s) and productivity (Q(p)) were 0 .41 g g(-1) and 0.44 g l(-1) h(-1), respectively, at an oxygen transfer rat e of 2.0 mmol O-2 l(-1) h(-1). The optimized results with this strain were compared to those of other xylose-fermenting yeasts and Saccharomyces cerev isiae (SSL-acclimatized) currently used at an industrial plant for the ferm entation of spent sulfite liquor.