(602a) Comparison of Fructose Production By Sequential vs. Simultaneous Saccharification and Isomerization of CELF Pretreated Corn Stover Solids

Authors: 
Alcaraz, C., University of California, Riverside
Kumar, R., University of California, Riverside
Christopher, P., University of California, Santa Barbara
Wyman, C. E., University of California
Christian Alcaraz1, 2, Rajeev Kumar2, Phillip Christopher,3 and Charles E. Wyman1, 2

1Department of Chemical and Environmental Engineering, Bourns College of Engineering, University of California, Riverside, Riverside, CA

2Center for Environmental Research and Technology (CE-CERT), Bourns College of Engineering, University of California, Riverside, Riverside, CA

3 Department of Chemical Engineering, Engineering II Building, University of California, Santa Barbara Santa Barbara, CA

Production of 5-HMF from cellulosic sugars could provide an attractive platform for conversion into drop-in fuels. Although pretreatment of cellulosic biomass can produce 5-HMF by dehydration of the glucose released, the high severities required to maximize 5-HMF yields increase operating costs and product losses due to humin formation. Alternatively, catalysts can convert glucose produced by pretreatment at lower severities into 5-HMF, but higher product yields result from using fructose that can be made from glucose. Glucose isomerization to fructose has been practiced commercially for over 40 years for production of sweeteners from corn syrup but not from glucose produced from cellulosic biomass. Thus, this research evaluated two alternative approaches with the objective to achieve high yields of fructose from the cellulose left in the solids produced by pretreatment of corn stover with a miscible mixture of tetrahydrofuran (THF) with water and dilute sulfuric acid known as Cosolvent Enhanced Lignocellulosic Fractionation or CELF. In the first, a two-step process was applied in which CELF solids were hydrolyzed by fungal enzymes to produce glucose followed by its isomerization to fructose by immobilized glucose isomerase (IGI) in a subsequent step. For the second approach, a “one-pot” strategy was applied in which the Clostridium thermocellum saccharified the glucan in CELF solids to glucose that IGI then isomerized to fructose in a single vessel. CELF pretreatment, enzymatic saccharification, and isomerization conditions were systematically varied to determine which of the two approaches achieved the highest fructose yields at affordable enzyme loadings.