Biomedical Engineering Reference
In-Depth Information
14.1.2.9
Serratia marcescens
Kim and Kwon [117] reported a microbial BOD biosensor consisting of
S. marcescens
LSY 4 and
an oxygen electrode. The polymer of sodium styrene sulfonate was grafted on the surface of porous
Tefl on membrane to absorb the heavy metal ions permeating through the membrane. Tolerance
against Zn
2
+
was induced for
S. marcescens
LSY 4 to make the cells less sensitive to the presence
of heavy metal ions. The membrane modifi cation and the Zn
2
+
tolerance induction showed some
positive effects in such a way that they reduced the inhibitory effects of Zn
2
+
and Cd
2
+
on the sen-
sitivity of the BOD sensor.
14.1.2.10
Rhodococcus erythropolis
R. erythropolis
is a kind of aerobic, Gram-positive actinomycete. It has unique enzymatic capabili-
ties for catalyzing the biotransformation and degradation of diverse xenobiotics. Due to its ability
to catalyze oxidation and metabolism of diverse and unusual substrates including hydrocarbons and
substituted phenols,
R. erythropolis
attracts interest in the area of bioremediation. The survival of
R. erythropolis
under adverse environmental conditions was higher than any other hydrocarbon-
utilizing bacteria.
Elena et al. [118] employed the whole cells of
R. erythropolis
as receptor and used a Clark-type
oxygen electrode as a transducer to form a microbial sensor for 2,4-dinitrophenol (2,4-DNP) deter-
minations. The response of this biosensor to 2,4-DNP was shown to add up, and it was considered
to originate from two components: the effect of 2,4-DNP as the respiratory substrate on the cells'
respiration of receptor element and the stimulatory effect of 2,4-DNP as protonophore on the cells'
respiration.
14.1.2.11
Trichosporon cutaneum
T. cutaneum
is a kind of yeast that can oxidize organic compounds. Yang et al. [119] fabricated a
miniature Clark-type oxygen electrode array and prepared a BOD biosensor based on
T. cutaneum
.
Each oxygen electrode of this array comprised an Ag cathode and an Ag/AgCl anode.
T. cutaneum
was immobilized onto the cathode of an oxygen electrode using a photo-crosslinkable resin, and
the sensor responded to the difference between the output of a yeast-immobilized electrode and that
of a bare oxygen electrode. The miniature oxygen electrode arrays showed good characteristics for
monitoring dissolved oxygen and could be mass-produced with assured quality.
Yano et al. [120] used
T. cutaneum
to develop a BOD microbial biosensor that applied to the
determination of amino acids produced in meat during the aging process. The biosensor consisted
of an oxygen sensor and a
T. cutaneum
membrane (Figure 14.3). The sensor signal corresponded
to the increase of amino acid levels and to the viable count in the meat with the storage time in the
course of the fi rst aging stage. This increase is due to the fact that amino acids produced initially
by enzymes in the meat serve as a source of nutrition for septic bacteria during the aging process,
and as a result, the level of bacterial cells increases with increasing amounts of amino acids with
the passage of time.
14.1.2.12
Saccharomyces cerevisiae
A new system is described for the amperometric detection of metal ions using recombinant
S. cerevi-
siae
strains as the biocomponent in the microbial sensor. For this purpose, plasmids were constructed
with the Cu
2
+
-inducible promoter of the
CUP1
-gene from
S
.
cerevisiae
fused to the promoterless
lacZ
-gene of
E
.
coli
. The fusion construct is only transcribed and translated in the presence of Cu
2
+
.
Subsequently, these plasmids were transformed into the yeast strains. Provided that Cu
2
+
is present,
the selected transformed cells are capable of utilizing lactose as an energy source [121]. The Cu
2
+
-
depending utilization of lactose leads to alterations in the oxygen consumption of the cells, which
can be measured by amperometric detection with a Clark oxygen electrode (Figure 14.4).
