Physico-chemical pretreatment and enzymatic hydrolysis of cotton stalk for ethanol production by Saccharomyces cerevisiae

The aim of this work was to study the physico-chemical pretreatment and enzymatic hydrolysis of cotton stalk for ethanol production by Saccharomyces cerevisiae. Firstly, factors affecting pretreatment were screened out by Plackett-Burman design (PBD) and most significant factors were further optimized by Box-Behnken design (BBD). As shown by experimental study, most significant factors were FeCl₃ concentration (FC), irradiation time (IT) and substrate concentration (SC) affecting pretreatment of cotton stalk among all studied factors. Under optimum conditions of pretreatment FC 0.15mol/l, IT 20min and SC 55g/l, the release of reducing sugar was 6.6g/l. Hydrolysis of pretreated cotton stalk was done by crude on-site produced enzymes and hydrolysate was concentrated. Ethanol production by Saccharomyces cerevisiae using concentrated cotton stalk hydrolysate was 9.8g_p/l, with ethanol yield 0.37g_p/g_s on consumed sugars. The data indicated that microwave FeCl₃ pretreated cotton stalk hydrolyses by crude unprocessed enzyme cocktail was good, and ethanol can be produced by fermentation of hydrolysate.