The Effect of Fed-Batch Operation and Rotational Speed on High-Solids Enzymatic Hydrolysis of Hardwood Substrates

Abstract

Abstract Enzymatic hydrolysis of hardwood substrates yields soluble sugars, which are a carbon source for producing ethanol and butanol. However, as the substrate and water are mixed, a viscous, heterogeneous slurry forms. The result is reduced mixing performance, mass transfer, and enzyme-substrate contact, all of which negatively affect sugar titers. In this study, enzymatic hydrolysis of a hardwood substrate at 20 wt% was conducted in a 10L stirred tank reactor. We investigated the dynamic changes in slurry behavior, as well as the interactions among mixer design/operation and fed-batch strategies. The effects of the number and frequency of substrate additions, impeller configuration, and high and moderate agitation speeds were evaluated using torque measurements and in terms of glucan-to-glucose conversion. Fewer additions corresponds to batch operation and negatively impacted solids distribution, accurate torque readings, and glucan conversion. However, as the number of additions incrementally increa...