An Update on Sulfite Pretreatment (sporl) of Lignocellulosic Biomass for Effective Production of Cellulose Ethanol

SPORL (Sulfite Pretreatment to Overcome Recalcitrance of Lignocellulose) has been demonstrated as an effective and robust pretreatment technology for ethanol production from lignocellulosic biomass, in particular woody biomass. The process consists of a short chemical treatment of feedstock with sulfite followed by mechanical size reduction (fiberization) with disk mill. Studies indicated that SPORL process is applicable to all types of feedstocks and directly deals with wood chips with regular size, and no extensive size reduction is required prior to the pretreatment. SPORL produced a readily digestible cellulose substrate because of the removal of hemicellulose and lignin, partial sulfonation of lignin (increased hydrophilicity and therefore reduced hydrophobic interaction with enzymes), depolymerization (prehydrolysis) of cellulose, and size reduction (increased surface area). The process has a high recovery yield of fermentable sugars with limited formation of fermentation inhibitors, which facilitates the fermentation of dissolved hemicellulosic sugars in pretreatment liquor. Lignin was partially dissolved in form of lignosulfonate with great potential for co-product development. In addition, the SPORL can directly adapt existing infrastructure and equipment in paper industry, which reduce the cost for equipment R&D and the risk of scale-up. This paper provides an update on our research in SPORL process.