(610b) Effects of Water-Soluble Polymer Addition On Alkaline Pretreatment and Enzymatic Hydrolysis of Switchgrass

Alkaline reagents such as ammonia and sodium carbonate have been used as pretreatment reagents to improve enzymatic saccharification of lignocellulosic biomass. Enhancement of digestibility is primarily caused by removal of major portion of the lignin. Residual lignin is believed to cause non-productive binding with cellulase during the enzymatic saccharification. Supplementation of small amounts of polymeric additives during the pretreatment is known to facilitate modification and redistribution of lignin. In order to assess the effects of polymer supplementation during pretreatment, various water-soluble polymers applied including cationic poly acrylamide (C-PAM), poly ethylene imine (PEI), poly-di-allyl-di-methyl ammonium (POLYDADMAC), and poly ethylene glycol (PEG). Switchgrass was used as the primary feedstock. Ammonium hydroxide and sodium carbonate were used as pretreatment reagents with polymer supplementation. Pretreatment experiments were carried out in batch reactors at temperature 60-90 °C, with residence time 6 - 24 hours, and liquid to solid ratio of 6-9. Pretreated samples were analyzed for composition with special attention on delignification and further examined by SEM and FTIR to observe the properties of the residual lignin. The treated samples were subjected to enzymatic saccharification using Novozymes Cellic CTec 2, and the results were analyzed in conjunction with the additives. The effects of additives on pretreatment and on enzymatic hydrolysis varied widely depending on the type of polymers. For certain additives, no effects were found on the extent of delignification, yet significant effects on the enzymatic hydrolysis. With this type of additives, the surface properties of the residual lignin found to be altered significantly by the additives.  The mechanisms by which the additives interact with biomass during pretreatment and during enzymatic hydrolysis are discussed in this study.