An improvement in Pichia stipitis fermentation of acid-hydrolysed hemicellulose achieved by overliming (calcium hydroxide treatment) and strain adaptation.

The fermentability of a corn cob, acid-hydrolysed hemicellulose by Pichia stipitis was considerably improved by pre-treatment with Ca(OH)2. The total sugars utilized and ethanol yield for the untreated hydrolysate were 18% and 0.21 g/g, respectively, compared with 82% and 0.32 g/g respectively for the treated material. Adaptation of the yeast to the hydrolysate resulted in a significantly higher fermentation rate with over 90% of the initial total sugars being utilized and an ethanol yield and maximum ethanol concentration of 0.41 g/g and 13.3 g/l, respectively.