Investigation of Catalytic Properties of Immobilized Enzymes and Cells by Flow Microcalorimetry - Advances in Biochemical Engineering Biotechnology - page 95

the reaction is not diffusion limited,the thermometric data are quite often used
directly for the determination of kinetic parameters in the denominator of the
kinetic equation (e.g. K m ,K i ). Similarly, the thermometric data provide infor-
mation for direct comparison of the relative activity of different IMB prepara-
tions, or of the same IMB under varied reaction conditions (e.g. pH-activity
profile). On the other hand, for the treatment of data obtained for a diffusion-
limited reaction, or when information about absolute biocatalyst activity is
required, it is convenient to convert the thermometric data to reaction rate
values. In order to do this, the transformation parameter, ,is calculated from

the experiment in the infinite recirculation mode.Then,after the data transfor-
mation,further computation is based on material balance equations.

a

7
Concluding Remarks

Experience shows that flow microcalorimetry is a universal technique that is
suitable for the investigation of the catalytic properties of immobilized bio-
catalysts. This review has summarized all basic examples of its application, but
has not exhausted all of their potential possibilities.As an example, the steady-
state measurement of a bi-substrate enzyme reaction with a co -immobilized
glucose oxidase-catalase system was reported [26]. However, there is no report
on the evaluation of kinetic properties of partial enzymes in co -immobilized
systems. Even the measurement of the overall heat produced in such systems
does not provide direct information about partial reactions.We believe that new
approaches to analyze these systems based on mathematical modeling can be
developed.
Besides steady state measurements,there is probably good reason to use flow
microcalorimetry for the study of non-steady-state behavior in systems with
immobilized biocatalysts.Here,the mathematical description is more complica-
ted, requiring the solution of partial differential equations. Moreover, the heat
response can evolve non-specific heats, like heat of adsorption/desorption or
mixing phenomena.In spite of these complications,the possibility of the on-line
monitoring of the enzyme reaction rate can provide a powerful tool for study-
ing the dynamics of immobilized biocatalyst systems.
Finally, the methodology summarized in this review indicates how easy it
would be to design universal measuring systems capable of performing experi-
ments on the catalytic properties of enzymes in an automatic way. This too is
our aim.

8
References

1. The Working Party on Immobilized Biocatalysts within the European Federation of Bio-
technology (1983) Enzyme Microb Technol 5:304
2. Ford JR,Lambert AH,Cohen W,Chambers RP (1972) Biotechnol Bioeng Symp 3:267
3. Buchholz K, Klein J (1987) Characterization of immobilized biocatalysts. In: Mosbach K
(ed) Methods in Enzymology,vol.135.Immobilized Enzymes and Cells,Part B.Academic
Press,Orlando,p 3