Xylose Utilization During Simultaneous Saccharification and Fermentation Enabled by a Parallel Microreactor with Immobilized Enzyme

One prominent challenge for the biochemical production of cellulosic ethanol is the utilization of xylose, which can increase ethanol yield 20-40% for typical feedstocks. Efforts toward genetic engineering of conventional yeast to utilize xylose have suffered from metabolic redox imbalance. This project will develop a technology for utilizing an industrial enzyme, glucose isomerase (GI), for the conversion of xylose to xylulose, which then can be metabolized to ethanol by conventional yeasts. The approach involves immobilizing GI in a microchannel reactor that recirculates the fermentation broth: the xylose is converted to xylulose and consumed during the fermentation step while enabling extended use of the expensive enzyme. In Phase I, a series of experiments will be conducted to extract the necessary kinetic parameters from a simple single-tube microreactor. These parameters will be used to model and fabricate a multichannel microreactor scaled for a 5 liter system. In Phase II, the design will be scaled up to a 100 liter system, and full automation of recirculation, pH control, and thermal management will be implemented. Commercial Applications and other Benefits as described by the awardee: Commercialization of this system should enable the widespread utilization of biomass resources for ethanol production in a sustainable manner, by obtaining greater yields from feedstock materials.