Thermal Biosensors in Biotechnology - Advances in Biochemical Engineering Biotechnology - page 44

Table 5. ET applications for process control

Analyte Immobilized Concentration Reference

compound [mmol/l]

acetaldehyde aldehyde dehydrogenase not mentioned Rank et al.1995

cellobiose b -glucosidase + glucose 0.05-5 Danielsson et al.1981a

oxidase + catalase
cephalosporin cephalosporinase 0.005-10 Danielsson et al.1981a

ethanol alcohol oxidase + catalase 0.002-1 Rank et al.1995

galactose galactose oxidase 0.01-1 Mattiasson et al.1982

L -glutamine glutaminase + glutamate 0.5-50 Lammers 1996

decarboxylase

glycerol glycerokinase not mentioned Rank et al.1995

L -lactate lactate oxidase + catalase 0.05-2 Danielsson et al.1994

lactose lactase + glucose 0.05-10 Mattiasson et al.1982

oxidase + catalase

maltose a -glucosidase + 0.15-6 Hundeck et al.1992

glucose oxidase

monoclonal anti-mouse-IgG 5-200 m g/ml Lammers 1996

antibodies
penicillin G b -lactamase 0.05-500 Mattiasson et al.1981

penicillin V penicillin acylase 0.5-150 Rank et al.1993

proinsulin anti-proinsulin-IgG 0.1-50 m g/ml Birnbaum et al.1986

sucrose invertase 0.1-100 Hundeck et al.1992

Hundeck et al.(1992) employed a four channel ET for on-line-monitoring of
glucose,maltose and sucrose during cultivation of Bacillus licheniformis .In this
process,microorganisms produce subtilisin,a serine protease added to washing
powders to improve washing efficiency. In fed-batch cultivations of Bacillus
licheniformis ,sucrose feed is a very important parameter because sucrose con-
centration correlates with subtilisin production.Optimal enzyme production is
achieved only within a defined sucrose range.Therefore,ET sucrose data were
used for maintaining a defined concentration range.
Figure 5 shows on-line-data of sucrose concentrations and the enzyme pro-
duction rate obtained during a fed-batch cultivation. Obviously, sucrose con-
centration and enzyme activity correlate.Due to growth ofthe microorganisms,
sucrose concentration decreases in the first five hours.After a lag, subtilisin is
produced at an optimum rate.The enzyme activity decreases after that because
the sucrose concentration is too low of a limited. Thus, sucrose is fed to the
medium and subtilisin production increases again.
In addition, the response time of immobilized yeast to different sugars was
used for monitoring and control of Bacillus licheniformis cultures (Hundeck et
al.1992).Specificity is not a characteristic of cell-based sensors;rather,they are
characterized by their ability to react in an integrated way to various stimuli.