title: Mechanistic kinetic models of enzymatic cellulose hydrolysis-A review.
abstract: Bioconversion of lignocellulose forms the basis for renewable, advanced biofuels, and bioproducts. Mechanisms of hydrolysis of cellulose by cellulases have been actively studied for nearly 70 years with significant gains in understanding of the cellulolytic enzymes. Yet, a full mechanistic understanding of the hydrolysis reaction has been elusive. We present a review to highlight new insights gained since the most recent comprehensive review of cellulose hydrolysis kinetic models by Bansal et al. (2009) Biotechnol Adv 27:833-848. Recent models have taken a two-pronged approach to tackle the challenge of modeling the complex heterogeneous reaction-an enzyme-centric modeling approach centered on the molecularity of the cellulase-cellulose interactions to examine rate limiting elementary steps and a substrate-centric modeling approach aimed at capturing the limiting property of the insoluble cellulose substrate. Collectively, modeling results suggest that at the molecular-scale, how rapidly cellulases can bind productively (complexation) and release from cellulose (decomplexation) is limiting, while the overall hydrolysis rate is largely insensitive to the catalytic rate constant. The surface area of the insoluble substrate and the degrees of polymerization of the cellulose molecules in the reaction both limit initial hydrolysis rates only. Neither enzyme-centric models nor substrate-centric models can consistently capture hydrolysis time course at extended reaction times. Thus, questions of the true reaction limiting factors at extended reaction times and the role of complexation and decomplexation in rate limitation remain unresolved. Biotechnol. Bioeng. 2017;114: 1369-1385. © 2017 Wiley Periodicals, Inc.
authors.affiliation: Biological and Agricultural Engineering, University of California, Davis, California.
authors.forename: Tina
authors.identifier: 0000-0002-0727-4237
authors.initials: T
authors.lastname: Jeoh
authors.affiliation: Chemical Engineering, University of California, Davis, California.|Intel Corporation, Hillsboro, Oregon.
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Cardona
authors.affiliation: Biological and Agricultural Engineering, University of California, Davis, California.|Department of Biotechnology, Faculty of Engineering and Industrial Technology, Silpakorn University, Nakhon Pathom, Thailand.
authors.forename: Nardrapee
authors.initials: N
authors.lastname: Karuna
authors.affiliation: Biological and Agricultural Engineering, University of California, Davis, California.
authors.forename: Akshata R
authors.initials: AR
authors.lastname: Mudinoor
authors.affiliation: Chemical Engineering, University of California, Davis, California.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Nill
mesh_terms: D001665:Binding Sites; D044602:Cellulases / Q000737:chemistry* / Q000648:ultrastructure*; D002482:Cellulose / Q000737:chemistry*; D003198:Computer Simulation; D004789:Enzyme Activation; D006868:Hydrolysis; D007700:Kinetics; D008956:Models, Chemical; D008958:Models, Molecular; D011485:Protein Binding; D013329:Structure-Activity Relationship
chemical_list: D002482:Cellulose; D044602:Cellulases
keywords: cellulase-cellulose interactions; cellulases; cellulose hydrolysis mechanism; cellulose structure; complexation and decomplexation; rate-limiting cellulose property