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Charles E Wyman, Rajeev Kumar, Vanessa A Thomas, Thanh Y Nguyen and Charles M Cai
University of California, USA
Posters & Accepted Abstracts: J Fundam Renewable Energy Appl
Our team recently invented a novel pretreatment called 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 or furfural, 5-hydroxymethylfurfural and levulinic acid for biological or catalytic conversion, respectively, into fuels and chemicals. Recovering highly volatile THF for recycle from post CELF, liquid precipitates nearly pure low molecular weight lignin for its potential valorization into fuels and chemicals. For biological conversion, CELF recovers about 90% of available sugars from hemicellulose while removing similar fractions of lignin. Of note, hydrolysis of CELF solids with just 2 mg enzyme/g glucan achieves nearly theoretical glucan yields, and simultaneous saccharification and fermentation (SSF) hydrolyzes and ferments about 90% of these solidsat5 mg-enzyme g-glucan-1. Consolidated bio-processing (CBP) with Clostridium thermocellum solubilizes most CELF glucan in 1 day without external enzyme addition. Alternatively, operating CELF at more severe conditions converts about 87% of pentose sugars to furfural for catalytic conversion, and glucan-rich solids can be further reacted with dilute acid to levulinic acid at about 75% of theoretical yield or digested to glucose with high yields at very low enzyme loadings. Additionally, CELF realized similar results with agricultural residues and recalcitrant hardwoods. In addition to its potential impact in increasing yields and reducing costly enzyme loadings for biomass deconstruction to sugars, the remarkable features of CELF can also be in valuable for gaining new insights into biomass deconstruction that suggest advanced approaches to overcoming recalcitrance, the key economic obstacle to fuels and chemicals from biomass. For example, enzymes show prolonged high activity over weeks for application to CELF pretreated solids at low enzyme loadings and do not suffer from the rapid drop off in enzyme action witnessed when such low enzyme loadings are applied to pure cellulose or solids produced by dilute acid or hydrothermal pretreatments. In addition to providing more details into application of CELF pretreatment to deconstruction of cellulosic biomass, an overview will be given of process strategies that can capitalize on these unique features.