OPTIMIZATION OF ETHANOL PRODUCTION BY SACCHAROMYCES CEREVISIAE (ATCC 60868) AND PICHIA STIPITIS Y-7124: A RESPONSE SURFACE MODEL FOR SIMULTANEOUS HYDROLYSIS AND FERMENTATION OF WHEAT STRAW

Abstract

Optimization models are useful in ascertaining optimum parameters as they relate to a particular response. Ethanol production with different cellulase-systems and substrate concentrations were subjected to this model and the results revealed that crude unextracted cellulase-systems are more efficient than crude extracted cellulase-systems in producing hydrolysates for ethanol production with Pichia stipitis (Y-7124), Saccharomyces cerevisiae (AT 60868) and their mixture. Response surface plots showed that for 80–90% of high concentrations of delignified wheat straw up to 11% could be converted into ethanol by simultaneous hydrolysis with enzyme loading of 16 IU/mL and fermentation with P. stipitis. P. stipitis was found to be the most suitable yeast for the fermentation of mixed hexose and pentose sugars in the wheat straw hydrolysate.