Monday, April 30, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
Cellulosic biomass is recalcitrant to enzymatic hydrolysis which greatly reduces the efficiency of biofuel production. Specifically, the lignin component of biomass is thought to provide non-productive binding sites for glycosyl hydrolases, effectively disabling the enzymes from completing further digestion. In the case of poor mixing, mass transport is dominated by diffusion rates and can significantly hinder the enzymatic hydrolysis. A thorough understanding of the diffusion-adsorption rates of protein molecules in celluloses - especially lignocelluloses - is crucial for improving the reaction kinetics and mixing strategies of the enzymatic digestion. We use magnetic resonance imaging to spatially resolve concentration profiles of bovine serum albumin (BSA) in various cellulosic fiber beds, including delignified and acid-treated lignocellulosic substrates. Effective diffusivities for BSA molecules were calculated using a numerical method from the MRI concentration profiles and compared with predictions of a diffusion-adsorption model in a porous medium. This model was previously verified for cellulosic substrates with MnCl2 as the diffusing solute. BSA is believed to be an effective adsorption blocker during enzymatic hydrolysis of lignocellulosics, and has been correlated with an increase in reaction yield. Results of the MRI experiments for adsorption were compared with ultraviolet (UV) absorption measurements at 280nm. We comment on the results in comparison with an adsorption study done at different reaction concentrations and conditions for BSA.