G. Handrikova et al., DETERMINATION OF EFFECTIVE DIFFUSION-COEFFICIENT OF SUBSTRATE IN GEL PARTICLES WITH IMMOBILIZED BIOCATALYST, Enzyme and microbial technology, 18(8), 1996, pp. 581-584
A method of determining of the effective diffusion coefficient of subs
trate in a particle, where the diffusion and consumption of substrate
by biocatalytic reaction are present simultaneously, was designed and
experimentally verified. The method is based on measuring the overall
rate of heterogeneous biocatalytic reaction in particles of varying di
ameter The effective diffusion coefficient D-e, was determined by fitt
ing the measured reaction rates with the solution of the reaction-diff
usion equation. The method is tailored for cases where the enzyme reac
tion is governed by the Michaelis-Menten kinetics. The value of K-m re
quired for the solution of the mathematical model was adopted from the
measurement of the kinetics of free cells, whereas the rate parameter
, k(2), was optimized together with D-e. As an experimental model, the
sucrose hydrolysis catalyzed by Ca-alginate-entrapped yeast cells was
examined. The particle diameter varied in the range of 1.2-3.9 mm and
the initial reaction rates were measured in a batch-stirred reactor a
t a sucrose concentration of 100 mM. The D-e of sucrose at 30 degrees
C was found to be 2.9 . 10(-10) m(2)s(-1).