Biomedical Engineering Reference
In-Depth Information
The analysis of substrate inhibition based on Eq. (38) was performed for immo-
bilized penicillin acylase as mentioned above.However,if particle mass transfer
can be neglected,an even simpler approach can be adopted,using the equation
that is valid for the differential bed
1-
e
c S
c S
a 7 V m
59625 = 59265 .
D
T r =
(39)
e
f(K m ,K i ,c S ,c i ) f(K m ,K i ,c S ,c i )
Since quantities in the first parenthesis are constant, they can be regrouped in
a single parameter,
. Thus, all parameters in the denominator of the kinetic
term can be determined directly by nonlinear regression from thermometric
data. Combining Eq. (39) with the kinetic model of the sucrose hydrolysis
catalyzed by invertase represented by Eq. (25) we obtain
c Sb
W
D
T r =
.
(40)
94936
K m + c Sb +c Sb W 0
K i
The last equation was used in several papers studying the kinetic properties of
invertase, where substrate inhibition was evaluated in terms of the inhibition
parameter K i [27,30,31].
5.5
Screening of Immobilized Biocatalysts
Flow microcalorimetry,which makes many rapid and accurate measurements of
the activity of immobilized biocatalysts, provides a tool for researchers that
can be used to discriminate between different preparatives of immobilized
biocatalysts. Table 3 shows previous experiments where the characterization
of kinetic properties by flow microcalorimetry was used to compare different
techniques of purified enzyme immobilization [27, 30, 31, 35] as well as the
immobilization of enzymes fixed in cells [28, 29, 40]. More details can be found
in our recent review article [41].
5.6
Monitoring of Enzymes Immobilized on Affinity Sorbents
While the interest in irreversible and covalent methods of immobilization con-
tinues,bioaffinity-based procedures are gaining appreciable attention,especially
for analytical applications [42]. Compared to other methods of immobilization,
those based on bioaffinity offer several distinct advantages.These include:
1. Binding of the enzyme to an affinity support may be very strong and yet
reversible under specific conditions;
2. The immobilization process is usually simple, and necessitates no special
skills;
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