Use of Co-Solvent Saves on Cost and Enzymes
Production of cost-effective biofuels from lignocellulosic biomass must overcome lignocellulose recalcitrance. Current processes to release sugars for viable biochemical conversion to biofuels requires energy-intensive pretreatment and large amounts of expensive enzymes. Researchers from the Department of Energy’s BioEnergy Science Center (BESC) have discovered that a new pretreatment called co-solvent-enhanced lignocellulosic fractionation (CELF) reduces enzyme costs dramatically, resulting in high sugar yields from hemicellulose and cellulose. CELF employs tetrahydrofuran (THF), which is miscible with aqueous dilute acid, and gives up to 95% of the theoretical yield of glucose, xylose, and arabinose from corn stover even when coupled with enzymatic hydrolysis at only 2 mg enzyme/g glucan—an unusually low concentration of enzymes. The unusually high saccharification with such low enzyme loadings can be attributed to very high lignin removal, which was evidenced by compositional analysis, fractal kinetic modeling, and scanning electron microscopy imaging. Subsequently, nearly pure lignin product was precipitated giving a clean lignin stream for valorization. THF was efficiently recovered and recycled by evaporation of the volatile solvent. Simultaneous saccharification of CELF-pretreated solids with low enzyme loadings and fermentation by Saccharomyces cerevisiae produced twice as much ethanol as that from dilute acid-pretreated solids after being optimized for corn stover. Thus, CELF offers efficient lignocellulosic biomass pretreatment and saccharification with reduced costs relative to current processes.
Nguyen, T. Y., C. M. Cai, R. Kumar, and C. E. Wyman. 2015 “Co-Solvent Pretreatment Reduces Costly Enzyme Requirements for High Sugar and Ethanol Yields from Lignocellulosic Biomass,” ChemSusChem, DOI: 10.1002/cssc.201403045.