Enhancing Enzymatic Hydrolysis of Maize Stover by Bayer Process Sand Pretreatment

In a laboratory study, enzymatic hydrolysis of maize stover pretreated with Bayer process sand (BPS) which is a waste with high alkalinity generated in aluminum production was compared with that of maize stover pretreated with sodium hydroxide. The effects of BPS loading, enzyme loading, pretreatment temperature, and pretreatment duration were investigated. After pretreatment at a BPS loading of 0.093 g NaOH equiv g maize stover, a temperature of 35 degrees C for 24 h, and at a cellulase enzyme loading of 15 FPU g glucan, 95.6% of the total amount of glucan and xylan contained in the pretreated maize stover was enzymatically hydrolyzed. In combination of the pretreatment and enzymatic hydrolysis stages, 93.2% of the glucan and 94.5% of the xylan were converted into glucose and xylose, respectively, similar to those obtained by means of sodium hydroxide pretreatment. Since the BPS solution contained 40-50 mg L aluminum ion (Al3+), the effect of Al3+ concentration on enzymatic hydrolysis of the maize stover pretreated with NaOH was examined. When Al3+ concentration was lower than 90 mg L, it did not affect enzymatic hydrolysis. These results suggest that BPS should replace sodium hydroxide for the pretreatment of maize stover.