(625x) Development of a Novel Simultaneous Saccharification and Isomerization (SSI) Approach to Enhance Fructose Production for Catalytic Conversion to Drop-in Fuels

Development
of a Novel Simultaneous Saccharification and Isomerization (SSI) Approach to
Enhance Fructose Production for Catalytic Conversion to Drop-In Fuels

Christian Alcaraz^{1, 2},
Rajeev Kumar², and Charles E. Wyman^{1, 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

Secondary
fuel precursors, e.g., furfural, HMF, and levulinic acid, made from sugars in cellulosic
biomass can be thermo-catalytically converted into ?drop-in? fuels, i.e.,
hydrocarbons that are compatible with the existing fuel infrastructure. Biological
saccharification of glucan using C. thermocellum in a consolidated
bioprocessing (CBP) approach promises to release glucose from glucan in biomass
with high yields without the need for a separate enzyme productions step,
thereby potentially reducing the cost compared to traditional cellulase enzymes.
 However, CBP is currently pictured to ferment the glucose released to ethanol
or other products while catalytic processes can realize higher yields product
yields from fructose than from glucose.  Thus, the objective of this research is
to develop a novel approach called simultaneous saccharification and
isomerization (SSI) to convert the glucose released by CBP into fructose from
glucan in a single step by coupling C. thermocellum CBP supplemented
with β-glucosidase to reduce glucan consumption by C. thermocellum
with simultaneous conversion of that glucose to fructose by glucose isomerase. 
Advantages of producing fructose directly from cellulose by employing wild type
C.thermocellum through SSI include 1) elimination of separate
enzyme production, 2) negligible or no requirement for adding expensive fungal
cellulases, 3) no need for genetic engineering, and 4) elimination of a
separate isomerization step.  As a first step in developing this novel concept,
50 g/L and higher concentrations of Avicel glucan was saccharified by C. thermocellum
supplemented with exogenous β-glucosidase and a commercial glucose
isomerase at 60°C to 70°C and pH of 6.0 to pH 7.5.