Biomedical Engineering Reference
In-Depth Information
the salicylate operon, thus gaining inducibility by salicylate or naphthalene [108,109], so it can be
used for the determination of naphthalene and salicylate bioavailability.
Trögl et al. [110] immobilized cells of
P. fl uorescens
HK44 to the thick silica fi lms prepared
from prepolymerized tetramethoxysilane. With these fi lms, the concentration of salicylate can be
detected to get a
P. fl uorescens
HK44 biosensor. The kinetics and response of such biosensors were
researched. It is concluded that there was a positive relationship between light emissions of immobi-
lized
P. fl uorescens
HK44 and salicylate as well as naphthalene concentration. It is also mentioned
that alginate appeared to be a very good immobilization material for further biosensor development
using
P. fl uorescens
HK44 because of its good transport properties with respect to napthalene and
salicylate.
Takayama et al. [111] constructed an electrochemical biosensor based on
P. fl uorescens
. They
immobilized whole cells of
P. fl uorescens
TN5 on the surface of carbon-paste electrodes containing
p
-benzoquinone or its derivatives. The electrodes produced anodic currents for nicotinic acid
because of the electrocatalytic action of the bacterial cells using the quinone compounds as an elec-
tron transfer mediator, and thus it could be used as a nicotinic acid biosensor.
14.1.2.7
Pseudomonas putida
Similar to
P. aeruginosa
and
P. fl uorescens,
P. putida
is also a kind of Gram-negative bacterium
that is an obligate aerobe and is used to develop highly sensitive biosensors for BOD detection [112].
In addition,
P. putida
ML2 has a special property of aerobic catabolism to benzene, thus it can be
used in the precise detection of benzene.
Lanyon et al. [113] have constructed a
P. putida
ML2 bacterial biosensor for the detection of
benzene that is integrated within a fl ow injection analysis (FIA) system.
P. putida
ML2 cells were
immobilized between two cellulose acetate membranes and fi xed onto a Clark dissolved oxygen
electrode. Biosensor responses were investigated with the FIA system, resulting in a linear detection
range between 0.01 and 0.1 mM benzene. This investigation demonstrates that the
P. putida
ML2
biosensor has potential applications for the analysis of samples containing benzene. Josef et al. [114]
developed another
P. putida
biosensor for the detection of whole benzene, toluene, ethylbenzene
(BTE), and xylene ranges. In this biosensor, the bacterial strains of
P. putida
F1 were immobilized
between two cellulose acetate membranes and fi xed onto a Clark dissolved oxygen electrode. The
P. putida
F1 aerobically degrades benzene, toluene, and BTE. The BTE biosensor in kinetic mode
FIA displayed a linear range of 0.02-0.14 mM benzene (response time, 5 min; baseline recovery
time, 15 min), 0.05-0.2 mM toluene (response time, 8 min; baseline recovery time, 20 min), and
0.1-0.2 mM BTE (response time, 12 min; baseline recovery time, 30 min. Due to the differences
in sensitivity, response, and baseline recovery times for BTE, it was possible to differentiate each
compound in mixtures of these volatile organic compounds (VOCs). No response for xylenes could
be obtained since they cannot be completely metabolized by this bacterial strain.
14.1.2.8
Klebsiella oxytoca
K. oxytoca
can exhibit high hydrogen production activity and high oxygen tolerance [115]. Ohki
et al. [116] used
K. oxytoca
AS1 to prepare a BOD biosensor. They mainly investigated the effect of
cell properties, such as the number and growth phase of immobilized cells, on the sensor response.
It is concluded that the response of such biosensor was almost independent of the cell number in the
case of low BOD solutions, whereas the response increased with increasing cell number when high-
BOD solutions were used. The growth phase of the cells immobilized in the membrane affected the
sensor response, especially when the membrane was stored at 30°C for a long time. Cells immo-
bilized at the beginning of the stationary growth phase were the most effective in terms of both
sensitivity and preservability. The biosensor showed a higher resistance to some toxic substances
such as phenol.
