Strategies to Achieve High-Solid Enzymatic Hydrolysis of Pretreated Corn Stover

Enzymatic hydrolysis of pretreated biomass is one of the key steps for biofuel and biochemical production. To make the overall process economically feasible, enzymatic hydrolysis at high-solid loading is necessary since it offers many advantages over at low-solid loading, including higher sugar concentration, lower capital cost in hydrolysis, reduced a burden in separation and purification process. However, the final sugar yield decreases with the increased solid loading. Based on the preliminary result with washed diluted acid pretreated corn stover, hydrolysis at 15% WIS (water insoluble solid) with an enzyme dosage of 5 FPU/g-substrate resulted in a final sugar concentration of 94.2 g/L, which was much higher than that of 31.4 g/L obtained at 5% WIS, while the final sugar yield was decreased from 77.3% to 69.3%. To achieve both a high sugar concentration and a high final sugar yield, three different multi-stage process configurations have been proposed and tested, including (1) fed-batch, (2) splitting/thickening, and (3) clarifier processes. At 15% WIS, the final sugar yield of 76.6% was obtained from the optimized fed-batch process after 96 hr of hydrolysis. For the splitting/thickening process, the total sugar yield was higher than the one-stage process from the second cycle. We will provide detailed description on the process concepts and comparison among the three strategies.