High solids quasi-simultaneous enzymatic saccharification and fermentation of un-detoxified whole slurry of sporl pretreated douglas-fir forest residue

Forest residue is the most affordable feedstock for biofuel production as stated in a recent US National Research Council Report. Softwood forest residue represents a significant amount of woody biomass that can be sustainably used to produce biofuel. It also has very low contents of acetyl groups and 5-carbon polysaccharides, favorable for biofuel production through yeast fermentation. However, it is highly recalcitrant to enzymatic saccharification due to high bark and lignin content. Most existing pretreatment processes are unable to remove this recalcitrance. Sulfite pretreatment to overcome the recalcitrance of lignocelluloses (SPORL) has demonstrated unparalleled performance for bioconversion of softwoods. In this study, we evaluated SPORL process for bioconversion of un-detoxified Douglas-fir forest residue at a high solids loading to ethanol.