(355b) Sulfite Pretreatment to Overcome Recalcitracne of Lignocellulose (SPORL) for Robust and Efficient Conversion of Biomass to Sugars

We will present a novel pretreatment process SPORL (Zhu et al., Bioresource Technology, 2411-2418, 2009; US Patent pending) for robust and efficient bioconversion of lignocellulosic biomass to sugars. The SPORL process is a mild chemical process using dilute sulfite solution to pretreatment biomass. Typical conditions are temperature between 170-190oC, pH ranges from 2 to 5, sulfite application on dry matter biomass solid of 1-8%, reaction time of 5-30 minutes in lab batch mode. At pretreatment temperature 180oC, we have achieved over 90% cellulose conversion to glucose for softwoods (the most recalcitrance of all biomass), such as spruce, red pine, lodgepole pine, in 40 hours with normal enzyme dosage of about 20 FPU/cellulose. Unlike most existing aqueous pretreatment processes, SPORL is effective when pretreatment is directly applied to chips or chops (not fiberized materials), which affords a low liquid to solid ratio of about 3 to significantly reduce thermal energy consumption in chemical pretreatment. Furthermore, SPORL produced excellent hemicellulsoe sugar recovery, e.g., xylose 75%, mannose 85%, as fermentable monomeric sugars in the spent pretreatment liquor. When SPORL is applied to hardwoods and agricultural residues, sulfite application dosage can be reduced to 2% on dry matter of solid biomass. Enzyme loading can be reduced half to achieve the same cellulose conversion of dilute acid pretreatment. SPORL also produced an order of magnitude less fermentable inhibitors than dilute acid pretreatment under the same temperature. SPORL is developed based on sulfite pulping process, therefore, it has excellent scalability for commercial deployment using mature infrastructure, and capital equipment to reduce technological barriers to building greenfield cellulosic ethnaol plants.