Microbial Remediation of Pesticides - Pesticides: Evaluation of Environmental Pollution - page 140

polluted ones (Fogg 1987; Gibson and Smith 1982; Sorkhoh et al. 1992). Unlike those of
heterotrophic microorganisms, the viability and metabolic activity of these cyanobacteria
are not subject to reduction by the decrease in the concentration of the pollutants that they
may break down (Kuritz and Wolk 1995). A recent report showed that a blue-green micro-
alga Spirulina platensis produces the enzyme, alkaline phosphatase. The purified enzyme
from the isolate, alkaline phosphatase, degraded 100 ppm chlorpyrifos to 20 ppm in 1 h,
transforming it into its primary metabolite, 3,5,6-trichloro-2-pyridinol (Thengodkar and
Sivakami 2010). The cyanobacterium Microcystis novacekii was found capable of remov-
ing methyl parathion, an organophosphorus pesticide, with an extraction rate higher than
90%, from the culture medium. This study showed that spontaneous degradation was not
significant, which indicates a high efficiency level of biological removal. No metabolites of
methyl parathion were detected in the culture medium when the concentration level was
evaluated (0.10 to 2.00 mg/dm 3 ) (Fioravante et al. 2010).
The synergistic coupling of microalgae propagation with carbon sequestration and
wastewater treatment potential for mitigation of environmental impacts associate with
energy conversion and utilization (Brennan and Owende 2010). Therefore, based on
current knowledge and technology projections, bioremediation using microalgae is
considered to be a technically viable alternative that is devoid of the major drawbacks
(gradual depletion of nutrients) associated with other microorganisms such as bacteria
and fungi.
5.7 Concluding Remarks
There are numerous biotic and abiotic factors acting as synergistic and antagonistic
effects in the microenvironment of the remediation site. Effects are interrelated while
the presence or absence of specific microbes may alter the procedure. For example, endo-
sulfan had a short-lived inhibitory effect on soil fungi, but bacteria increased in number
in response to endosulfan application (Joseph et al. 2010). Screening of functional genes
in coral-associated microbial communities revealed 6700 genes, providing evidence
that the coral microbiome contains a diverse community of archaea, bacteria, and fungi
capable of fulfilling numerous functional niches. These included carbon, nitrogen, and
sulfur cycling; metal homeostasis and resistance; and xenobiotic contaminant degrada-
tion (Kimes et al. 2010).
The literature on bioremediation is huge, and only selected examples of microbial
strains' potential for use in bioremediation processes of pesticides are provided in this
chapter. Some of the microbial strains described could be combined or improved through
genetic manipulation. In other cases, appropriate detailed knowledge of microbes, pesti-
cides, and environment of the specific site may allow further optimization of the desired
process by altering the physicochemical conditions of the contaminated area. A combi-
nation of genetic engineering with appropriate ecoengineering of polluted sites may be
relevant to some future bioremediation strategies (Valls and de-Lorenzo 2002). All kinds
of microbes, including prokaryotes and eukaryotes and their symbiotic associations
with each other and “higher organisms” including humans, play remarkably wide and
diverse geoactive roles in the biosphere. Increasing our understanding of microbiology
and exploiting it in bioremediation and other areas of biotechnology clearly require a