Bioconversion of woody biomass to biofuel and lignin co-product using sulfite pretreatment to overcome the recalcitrance of lignocelluloses (SPORL)

Abstract

Sulfite pretreatment to overcome the recalcitrance of lignocelluloses (SPORL) promises to provide efficient bioconversion of woody biomass into bioethanol and lignin co-products. Results from several laboratory and pilot-scale studies are presented to demonstrate SPORL performance, with comparisons to competing technologies. Excellent ethanol yields of up to approximately 80% theoretical, based on glucan, mannan, and xylan content of wood, were achieved at titers over 40 g/L. This high productivity was accomplished using low cellulase loadings, 26 mL/kg wood, and without detoxification, solid–liquor separation, or supplementation of nutrients in fermentation. Lignin sulfonation from SPORL likely contributes to this high efficiency by reducing nonproductive binding of cellulase through electrostatic repulsion and reduced hydrophobic interactions between cellulase and lignin. Finally, a reaction-kinetics-based severity factor—the combined hydrolysis factor (CHF)—was developed to facilitate process scale-up and for determining optimum operating conditions for balancing sugar yield against sugar degradation.

Citation

Zhu J.Y.; Zhang, Chao; Gleisner, Rolland; Houtman, Carl J.; Pan, Xuejun. 2016. Bioconversion of woody biomass to biofuel and lignin co-product using sulfite pretreatment to overcome the recalcitrance of lignocelluloses (SPORL). General Technical Report FPL-GTR-240. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 34 p. https://doi.org/10.2737/FPL-GTR-240