Development and Validation of a Model for Cellulase Diffusion, Adsorption and Reaction In Wood Particle

In the pretreatment process of biofuel production, the use of woody biomass such as hybrid poplar and lodgepole pine requires an energy intensive size reduction step. Optimization of wood particles with respect to specific size and shape not only reduces the energy cost for size reduction, but also facilitates downstream biochemical conversion. Modeling enzyme behavior in wood particles can provide useful information for wood particle design. In this study, cellulase diffusion, adsorption, and reaction in wood particles were modeled using simulation software "COMSOL Multiphysics".  The model predicted that physical dimensions and vascular characteristics of the wood particle had great influence on the enzyme diffusion into wood. The adsorption of cellulases on cellulose and lignin also played an important role in enzymatic hydrolysis. Experiments supporting this model comprised measurements of enzyme and sugar concentrations both in bulk solution and inside the wood particle. The hydrolysis experiment was carried out using a range of wood particle sizes from 1 mm to 6 mm derived from different size reduction approaches. The model described the enzyme and sugar concentration profiles during hydrolysis accurately and can be used to optimize wood particle design for pretreatment and saccharification, as well as to provide essential information for reactor and process design of biofuel production.

Figure 1 enzyme concentration profile in 8 tracheids wood particle model