Effects of water-soluble polymer on enzymatic saccharification of lignocellulosic biomass

Supplementation of surface active reagents during enzymatic saccharification of biomass is known to increase the activity of cellulase. The role of these reagents is to reduce the unproductive binding of cellulase enzymes with lignin. Some of proven cellulase enhancers that follow this mechanism include bovine serum albumin, polyethylene glycol, and Tween-80. Use of these additives is expected to reduce the enzyme dosage in the bioconversion processes by 20-40%, a significant economic benefit. In this work to evaluate the effect of additives on enzymatic hydrolysis different water-soluble polymers were studied including polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, cationic polyacrylamide, and polyethylene imine. To evaluate the effect of presence of lignin various feedstocks including Solka Floc and hardwood pulp (lignin free substrates), dilute sulfuric acid pretreated corn stover, dilute sulfuric acid pretreated switchgrass, aqueous liquid ammonia pretreated switchgrass (lignocellulosic substrates) were used. Enzymatic hydrolysis experiments were carried out with 5 FPU/g-glucan of C-Tec 2 and 5% solids loading. Results indicate that supplementation of 10 mg polymer/g-substrate increased the glucan digestibility by 10-30% depending on type of the substrate and polymer. About the same level of increase in xylan digestibility was also observed. To further investigate the role of the polymers, enzymatic hydrolysis was performed for lignin-free substrates and the results were compared with those of pretreated lignocellulosic substrates. Protein assay based on BSA standard was also performed under various conditions. The results collectively indicate that the polymer effect is mainly on the enzyme adsorption onto the substrate surface causing the overall enzymatic reaction.