Statistical optimization of dilute sulfuric acid pretreatment of corncob for xylose recovery and ethanol production

The interest on use of lignocellulose for producing fuels and chemicals is increasing as these materials are low cost, renewable and widespread sources of sugars. Corncob is an attractive raw material for xylose and fuel ethanol production due to its high content of xylan and glucan. In this study, the central composite design of response surface method was used to optimize dilute H2SO4 pretreatment of corncob, in respect to acid concentration (0.16–1.84%), treatment time (0.16–1.84 h) and temperature (105–130 °C) for xylose production. Enzymatic hydrolysis of the remaining solid was carried out further to evaluate the acid pretreatment conditions for maximizing glucose production. The results showed that pretreatment conditions for the highest xylose production was 1% sulfuric acid for 1.5 h at 123 °C, corresponding to 87.2% total xylan converted to xylose and that for the highest glucose + cellobiose recovery was 0.5% sulfuric acid for 30 min at 125 °C, corresponding to 78.1% total glucan converted to glucose + cellobiose. In the subsequent simultaneous saccharification and fermentation (SSF) experiments using 14% glucan substrates pretreated under above two kinds of conditions, 47 g l−1 ethanol with a 65.8% theoretical yield and 50.2 g l−1 ethanol with a 70.4% theoretical yield were obtained, respectively.