6 Biotechnological Approaches for Pollutant Detection
In recent years, environmental pollution detection and monitoring are being done
by approaches involving bio-systems. For this, purpose, several groups of plants,
animals and microorganisms are utilized. The environmental protection agencies
consider bio-monitoring of pollution as a useful device to monitor environmental
pollution from the point of diagnostic, preventive and remedial measures.
The biotechnological methods adopted for pollution measurement can be briefly
described in the following: (a) General bioassays; (b) Cell biological assays;
(c) Molecular biological assays; (d) Biosensors.
(a) General bioassay
In the early years, conventional physical and chemical methods were used for the
detection of environmental pollution. Bioassays are preferred these days since the
biological responses that reflect the damages to the living organisms are very crucial
for the actual assessment of pollution. Certain algae, bacteria, lichens, mosses and
vascular macrophytes are commonly used in bioassays.
Among the plant systems, algal bioassays are the most commonly used. Algae
are considered to be reliable indicators of pollution due to their high sensitivity and
easy availability, besides simple culturing techniques. The criteria adopted for algal
bioassays are the growth rate, biomass accumulation and photosynthetic efficiency.
The algae used in the test assays include Chlorella, Microcystis, Spirulina,
Navicula, Scenedesmus, Anabaena, Ulva, Codium, Fucus and Laminaria. In water,
organic pollution can be detected by using the blue-green algae, Microcystis, while
metal pollution can be measured by Navicula.
Lund Yi et al. (1984) reported a sensitive, simple and rapid bioassay involving
two-species of marine algae for the determination of the toxicity of chemical contaminants. The bioassay employs the marine diatoms Phaeodactylum tricornutum
and Cyclotella cryptica. After screening 40 clones of 32 species, an optimum pair i.e.
P. tricornutum and C. cryptica were selected. These algal species are easily cultivated in the laboratory environment, and the algal cells can be differentiated and
enumerated with the help of electronic particle counter. For the sake of toxicity
determination alteration of species ratio and total biomass were applied.
Polychlorinated biphenyls at 10 parts per thousand million (10
9 ; ptm) considerably
transformed species ratio in the favour of P. tricornutum, and 10 ptm of DDT (l,
l,1-trichloro-2,2-bis(p-chlorophenyl)ethane) and 20 ptm of dieldrin produced a
significant species alteration in contrast to that created by polychlorinated biphenyls.
Bacterial bioassays are commonly used for the detection of faecal pollution in
potable water, the most widely employed test being the coliform test. Ames test that
detects mutagenic pollutants is carried out by the bacterium Salmonella. Bacterial
bioluminescence is a recent technique used for the measurement of gaseous pollutants and other compounds e.g. sulfur dioxide, formaldehyde, ethyl acetate.
Photobacterium phosphoreum is the organism of choice for bacterial
bioluminescence.
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R. Khan et al.
In recent years, environmental pollution detection and monitoring are being done
by approaches involving bio-systems. For this, purpose, several groups of plants,
animals and microorganisms are utilized. The environmental protection agencies
consider bio-monitoring of pollution as a useful device to monitor environmental
pollution from the point of diagnostic, preventive and remedial measures.
The biotechnological methods adopted for pollution measurement can be briefly
described in the following: (a) General bioassays; (b) Cell biological assays;
(c) Molecular biological assays; (d) Biosensors.
(a) General bioassay
In the early years, conventional physical and chemical methods were used for the
detection of environmental pollution. Bioassays are preferred these days since the
biological responses that reflect the damages to the living organisms are very crucial
for the actual assessment of pollution. Certain algae, bacteria, lichens, mosses and
vascular macrophytes are commonly used in bioassays.
Among the plant systems, algal bioassays are the most commonly used. Algae
are considered to be reliable indicators of pollution due to their high sensitivity and
easy availability, besides simple culturing techniques. The criteria adopted for algal
bioassays are the growth rate, biomass accumulation and photosynthetic efficiency.
The algae used in the test assays include Chlorella, Microcystis, Spirulina,
Navicula, Scenedesmus, Anabaena, Ulva, Codium, Fucus and Laminaria. In water,
organic pollution can be detected by using the blue-green algae, Microcystis, while
metal pollution can be measured by Navicula.
Lund Yi et al. (1984) reported a sensitive, simple and rapid bioassay involving
two-species of marine algae for the determination of the toxicity of chemical contaminants. The bioassay employs the marine diatoms Phaeodactylum tricornutum
and Cyclotella cryptica. After screening 40 clones of 32 species, an optimum pair i.e.
P. tricornutum and C. cryptica were selected. These algal species are easily cultivated in the laboratory environment, and the algal cells can be differentiated and
enumerated with the help of electronic particle counter. For the sake of toxicity
determination alteration of species ratio and total biomass were applied.
Polychlorinated biphenyls at 10 parts per thousand million (10
9 ; ptm) considerably
transformed species ratio in the favour of P. tricornutum, and 10 ptm of DDT (l,
l,1-trichloro-2,2-bis(p-chlorophenyl)ethane) and 20 ptm of dieldrin produced a
significant species alteration in contrast to that created by polychlorinated biphenyls.
Bacterial bioassays are commonly used for the detection of faecal pollution in
potable water, the most widely employed test being the coliform test. Ames test that
detects mutagenic pollutants is carried out by the bacterium Salmonella. Bacterial
bioluminescence is a recent technique used for the measurement of gaseous pollutants and other compounds e.g. sulfur dioxide, formaldehyde, ethyl acetate.
Photobacterium phosphoreum is the organism of choice for bacterial
bioluminescence.
264
R. Khan et al.