(578b) Advances in the Biomass-to-Bioproduct Processing Chain to Produce 2-Pyrone-4,6-Dicarboxylic Acid Via Reductive Catalytic Fractionation Followed By Microbial Funneling

Catalytic, enzymatic, and microbial conversion are used in different stages of the new generation biorefineries. In an integrated biomass-to-bioproduct processing chain, these processes are interrelated, and this makes the optimization of the overall processing chain challenging. The biggest pitfall in developing these processes is the mismatch between the goals of catalytic fractionation of biomass and subsequent biological/enzymatic upgrading.

In our previous work, we used chemical and biological upgrading in tandem to extract greater value from the lignin fraction by converting a fraction of lignin to high value 2-pyrone-4,6-dicarboxylic acid (PDC). Reductive Catalytic Fractionation (RCF) was used to liberate lignin from the biomass and simultaneously depolymerize the lignin through catalytic hydrogenolysis. Using an engineered strain of Novosphingobium aromaticivorans DSM12444, the RCF product mixture can be upgraded to PDC. By applying RCF to the poplar with Pd/C as catalyst and methanol as solvent; we were able to have increased monomer/oligomer product yield and the PDC yield on a per kg of biomass basis compared to a stepwise lignin isolation followed by hydrogenolysis of fractionated lignin. Furthermore, the sugar stream of the lignocellulosic biomass which was preserved after RCF process, was subjected to enzymatic and microbial digestion to produce liquid fuels. Combined, we produced value added products from both the lignin (phenolics) and polysaccharide fractions.

Technoeconomic analyses of our processing chain indicated that the RCF stage is costly because of the high-pressure reaction conditions due to low boiling point of methanol. Changing the solvent from methanol to a higher boiling point one will not only improve the process economics but also improve the safety of process operation. For this purpose, ethylene glycol, ethanol and ethanol-water mixture were tested. In our processing chain, using these solvents with reduced reaction pressure have shown that similar lignin monomer yields with methanol as solvent can be achieved. Initial experiments showed that these solvents are not detrimental to microbial upgrading and similar PDC yields could be obtained. Further process optimization was performed by varying the reaction time, solid concentration, biomass/catalyst ratio, and the effect of these changes on the microbial funneling to PDC was determined.