Biomedical Engineering Reference
In-Depth Information
14.1.2.4
Gluconobacter oxydans
G. oxydans
cells contain membrane-bound aldose dehydrogenase, which catalyzes the oxidation of a
wide range of sugars including all sugars present in lignocellulose hydrolysate [101]. Tkác et al. [102]
prepared a microbial biosensor by surface modifi cation of a graphite electrode with
G. oxydans
cells and enhanced the sensitivity of amperometric detection by using hexacyanoferrate(III) as a
mediator. The biosensor was used for the determination of total sugars during lignocellulose hydro-
lysate fermentation including d-glucose, d-galactose, d-xylose, d-mannose, and l-arabinose, and a
good correlation was obtained between total sugars determined by the biosensor and by quantitative
paper chromatography.
Reshetilov et al. [103] immobilized
G. oxydans
whole
cells on a FET to detect xylose by moni-
toring extracellular pH changes resulting from xylose dehydrogenation. This FET-based biosensor
could detect xylose at a lower limit of 0.5 mM and could keep a linear range of 5.0-30 mM. Resheti-
lov et al. [104] also immobilized whole cells of
G. oxydans
on chromatographic paper by simple
physical adsorption and attached those cells to the surface of the Clark-type electrodes for xylose
determinations. In contrast with the xylitol above-mentioned biosensor, the detection of xylose by
this biosensor was not signifi cantly affected by the presence of xylitol. It is suggested that this bio-
sensor will be useful in monitoring conversions of the compounds of xylose and xylitol.
14.1.2.5
Pseudomonas aeruginosa
P
.
aeruginosa
is a representative bacterium of the genus
Pseudomonas
and belongs to aerobic bacte-
ria. It is repor ted that
P
.
aeruginosa
JI-104 can aerobically degrade trichloroethylene (TCE) as a sole
carbon source [105]. The overall pathway of oxidative TCE degradation by
P. aeruginosa
JI-104 is
predicted as follows: TCE is transformed to TCE oxide, which becomes dichloroacetic acid, glyox-
ylate, carbon monooxide, or formic acid successively, and fi nally carbon dioxide is produced. Han
et al. [105] immobilized
P. aeruginosa
JI-104 isolated from the soil near a gasworks on a polytet-
rafl uoroethylene (PTFE) fi lter and mounted onto chloride ion electrode to form a novel microbial
TCE sensor. Dihaloelimination occurs during the biological transformation of TCE and chloride
ion concentration is measured, and thus it is possible to predict the initial TCE concentration.
Elasriá et al. [106] fused the
P. aeruginosa
recA promoter to a promoterless
Vibrio fi scheri
lux operon. This recA-lux fusion (pMOE15) was introduced into a wild-type
P. aeruginosa
strain
FRD1, and recA expression was monitored by measuring 490 nm light production. The RM4440
strain responded to the increasing doses of ultraviolet radiation by an increase in its biolumines-
cence. RM4440 has the potential to be useful as a biosensor for the measurement of DNA-damaging
agents in the environment.
P. aeruginosa
can produce a kind of blue phenazine pigment, pyocyanin, which exists in the
oxidated form and was reduced by the reaction between GOD and glucose. The reduced form was
then converted back to the oxidized form by an oxidative reaction [107]. Kunihiko et al. [107] pro-
duced pyocyanin by immobilized
P. aeruginosa
cells in κ-carrageenan under a 0.01% PO
3
−
, 0.2%
Mg
2
+
, 0.001% Fe
2
+
, 1% glycerin, 0.8% leucine, and 0.8% dl-alanine condition. Then pyocyanin
purifi ed by chloroform extraction and silica-gel column chromatography was used as a media-
tor fi xed on a screen-printed electrode to prepare a biosensor for more accurate determination of
glucose concentration.
14.1.2.6
Pseudomonas fl uorescens
P. fl uorescens
HK44 harbors the pUTK21 plasmid (derived from the NAH7 plasmid), which codes
for genes of the naphthalene degradation pathway and is divided into two operons. Both the oper-
ons are positively inducible by salicylate through the
nahR
gene product, therefore little of their
activity is present constitutively, and a huge increase of activity is observed after induction. The
V. fi scheri luxCDA BE
gene cassette coding for bioluminescence was inserted into the
nahG
gene of
