Presenter: Dr. Charles Wyman 

Ford Motor Company Chair in Environmental Engineering Center for Environmental Research and Technology (CE-CERT) and Professor of Chemical and Environmental Engineering

Bourns College of Engineering, University of California

Title: Co-Solvent Enhanced Lignocellulosic Fractionation (CELF): A Novel Pretreatment to Increase Precursor Yields from Cellulosic Biomass for Biological or Catalytic Conversion to Fuels

Abstract: Our team recently invented a novel pretreatment we call Co-solvent Enhanced Lignocellulosic Fractionation (CELF) that applies renewable, water-miscible tetrahydrofuran (THF) with dilute sulfuric acid to fractionate cellulosic biomass and achieve high yields of sugars for fermentation or furfural, 5-hydroxymethylfurfural, and levulinic acid for catalytic conversion into fuels and chemicals.  Recovering highly volatile THF for recycle from post CELF liquid precipitates nearly pure lignin that could be a valuable resource for making fuels, chemicals, and materials.  For biological conversion, CELF pretreatment at 150°C for 25 minutes with 0.5% sulfuric acid recovered over 90% of available sugars from hemicellulose while removing similar portions of lignin.  Of particular importance, subjecting CELF solids to just 2 mg enzyme/g glucan achieved nearly theoretical glucose yields, and simultaneous saccharification and fermentation (SSF) of CELF pretreated solids hydrolyzed and fermented about 90% of the glucan at 5 mg-enzyme g-glucan^-1. Consolidated bioprocessing (CBP) with Clostridium thermocellum solubilized most CELF glucan in 1 day without external enzyme addition. Application of more severe conditions to CELF converted about 87% of pentose sugars to furfural that could be used for catalytic conversion, and the remaining solids that were highly enriched in glucan could be further reacted with dilute sulfuric acid to levulinic acid at about 75% of theoretical maximum or digested to glucose with high yields at very low enzyme loadings.  Adding metal halide acids, e.g., FeCl₃, increased theoretical yields to about 95% and 51% for furfural and 5-HMF, respectively, in one vessel. CELF also proved capable of realizing similar results with agricultural residues and recalcitrant hardwoods.  In addition to its potential commercial value for substantially lowering enzyme loadings needed to realize high yields, the remarkable features of CELF can be invaluable for gaining new insights into biomass deconstruction and suggest advanced approaches to overcoming recalcitrance, the key economic obstacle to making fuels and chemicals from cellulosic biomass.