title: Modeling the kinetics of enzymic reactions in mainly solid reaction mixtures.
abstract: There is currently considerable interest in using mainly solid reaction mixtures for enzymic catalysis. In these reactions starting materials dissolve into, and product materials crystalize out of, a small amount of liquid phase in which the catalytic reaction occurs. An initial mathematical model for mass transfer effects in such systems is constructed using some physically reasonable approximations. The model equations are solved numerically to determine how the reactant concentrations vary with time and position. To evaluate the extent to which mass transfer limits the overall rate of product formation, an effectiveness factor is defined as the ratio of the observed total reaction rate to the total reaction rate in the reaction limited limit. As expected, the value of the effectiveness factor in steady state is strongly dependent on the Thiele modulus. However, it is also observed that the effectiveness factor can vary widely as a result of changes in the other dimensionless groups characterizing the system. For example, there are situations with Thiele modulus equal to unity in which the value of the effectiveness factor varies between approximately 0.1 and 0.8 as the other parameters are varied in physically reasonable ranges. Analytical asymptotic solutions that provide good approximations to the numerically calculated results in various physically important limiting cases are also presented.
authors.affiliation: Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow G1 1XL, United Kingdom.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Halling
authors.forename: Stephen K
authors.initials: SK
authors.lastname: Wilson
authors.forename: Ralf
authors.initials: R
authors.lastname: Jacobs
authors.forename: Sean
authors.initials: S
authors.lastname: McKee
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Coles
mesh_terms: D045424:Complex Mixtures / Q000737:chemistry*; D003198:Computer Simulation; D004789:Enzyme Activation; D007700:Kinetics; D008956:Models, Chemical; D044367:Phase Transition; D012997:Solvents
chemical_list: D045424:Complex Mixtures; D012997:Solvents