Investigation of Catalytic Properties of Immobilized Enzymes and Cells by Flow Microcalorimetry - Advances in Biochemical Engineering Biotechnology - page 83

Input sucrose concentration (mmol L -1 )
Fig. 8. Flow microcalorimetric investigation of kinetic properties of invertase bound to
Eupergit C activated by concanavalin A. The line corresponds to calculated data. The model
involving high substrate conversion was used and parameters were estimated by nonlinear
regression:V m =1950 mM min -1 ,K m =3420 mM,K i =246 mM,P=2.7 K (unpubl.results)
The results of the experimental study and mathematical modeling of the
invertase-catalyzed hydrolysis of sucrose are displayed in Fig. 8.The analysis of
the output substrate concentration showed substantial substrate conversion.
Therefore,the data were treated by differential equations (26) and (30),whereas
the kinetic parameters were fitted using nonlinear regression.Regardless of the
good agreement of the calculated and experimental values,it was concluded on
the basis of a comparison of kinetic parameters obtained with those known
from previous works on similar preparations of immobilized invertase [30] that
this method did not provide reliable results.
In contrast, the measurement of the kinetic properties of immobilized
urease under conditions of high substrate conversion resulted in “good” data
[25]. Evidently, the increased substrate conversion in the microcalorimetric
column increases the change in temperature.Thus,better control of heat loss is
necessary.Moreover,the treatment of data of integral reactor is more complicat-
ed, and can lead to larger errors of parameter estimates. In spite of these diffi-
culties, it is worth putting more effort into the development of methods based
on higher substrate conversion because it could be very useful in the investiga-
tion of product inhibition effects and in the case of enzyme reactions with low
enthalpy of reaction.
5.1.3
Enzyme Systems Influenced by Particle Diffusion Limitation
Many immobilization techniques provide biocatalysts in which the enzyme is
immobilized in the porous structure of the biocatalyst particle.In such cases,the