in 1937 (Dragun et al. 1984). Organophosphorus pesticides have been widely
developed for agricultural purposes since the 1950s, and these pesticides are highly
toxic chemicals (Gupta 2009). The acute toxicity of organophosphorus chemical
compounds is due to their capacity to inhibit acetylcholine esterase, a key enzyme
involved in the overall regulation of the central and peripheral nervous system. As
the organochlorine pesticides such as lindane, dichloro-diphenyl-trichloroethane
(DDT) possess longer persistency, tendency towards bioaccumulation, high mammalian toxicity, and potential toxicity towards non-target organism, the use of these
has been diminished drastically in developed countries and has been replaced by the
less persistent and more effective and efficient other similar organophosphorus
compounds such as chlorpyrifos, glyphosate, methyl parathion, parathion, diazinon,
coumaphos, fenamiphos, monocrotophos and phorate. The phosphorus is generally
present as a phosphonate or a phosphate ester which are normally involved in
oxidation, hydrolysis, dealkylation and alkylation. Therefore, the most important
step in detoxification by microbial degradation involves through hydrolysis of P-Oaryl and P-O-alkyl bonds. Singh and Walker (2005) have presented a list of
microorganisms capable of degrading organophosphorus compounds.
Although pesticides play a key role in the protection of crop yields, their
excessive and persistence use resulted in serious soil pollution and deteriorated
soil quality. Excessive and continuous use of these compounds has led to the
contamination of several ecosystems in different parts of the world (Cisar and
Snyder 2000; Tse et al. 2004). Residues of pesticides have been reported in soil,
water, milk, food, or fish in numerous countries around the world. As these compounds possess high toxicity and constitutes major health and environments issue
(Jaipieam et al. 2009), it is essential to remove them from the environment. Numerous approaches including physical, chemical and biological methods have been
considered for developing decontamination strategies against these chemicals, but
these methods are not considered for large-scale environmental remediation and also
involve harsh conditions (Jacquet et al. 2016). Hence, bioremediation, the treatment
that uses living organisms to transform hazardous substances into lesser or non-toxic
compounds, is an effective way to clean up the soil polluted with chemical pesticides. The first microbe, Flavobacterium sp. that could degrade organophosphorus
compounds was isolated and identified in 1973, and subsequently, several bacterial
and a few fungal species have been isolated which can degrade a wide range of these
compounds in soil systems and liquid cultures. The degradation process of these
compounds takes place through the enzymes organophosphate hydrolase or
phosphotriesterase catalyse encoded by gene opd (organophosphate degrading)
which has been isolated, sequenced, cloned in different organisms and altered for
better activity and stability (McDaniel et al. 1988; Horne et al. 2002).
In recent years, enzymes from extremophiles have emerged as promising alternative to smoothly and quickly decontaminate these chemical compounds. The
phosphotriesterase-like lactonase ScoPox from the archaea Sulfolobus solfataricus
is an attractive candidate for bioremediation. This enzyme has been engineered and
proven to be highly efficient for degrading a number of organophosphorus pesticides
(Elias et al. 2008; Hiblot et al. 2012, 2013; Del Giudice et al. 2016). Two
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S. Kaushik et al.
developed for agricultural purposes since the 1950s, and these pesticides are highly
toxic chemicals (Gupta 2009). The acute toxicity of organophosphorus chemical
compounds is due to their capacity to inhibit acetylcholine esterase, a key enzyme
involved in the overall regulation of the central and peripheral nervous system. As
the organochlorine pesticides such as lindane, dichloro-diphenyl-trichloroethane
(DDT) possess longer persistency, tendency towards bioaccumulation, high mammalian toxicity, and potential toxicity towards non-target organism, the use of these
has been diminished drastically in developed countries and has been replaced by the
less persistent and more effective and efficient other similar organophosphorus
compounds such as chlorpyrifos, glyphosate, methyl parathion, parathion, diazinon,
coumaphos, fenamiphos, monocrotophos and phorate. The phosphorus is generally
present as a phosphonate or a phosphate ester which are normally involved in
oxidation, hydrolysis, dealkylation and alkylation. Therefore, the most important
step in detoxification by microbial degradation involves through hydrolysis of P-Oaryl and P-O-alkyl bonds. Singh and Walker (2005) have presented a list of
microorganisms capable of degrading organophosphorus compounds.
Although pesticides play a key role in the protection of crop yields, their
excessive and persistence use resulted in serious soil pollution and deteriorated
soil quality. Excessive and continuous use of these compounds has led to the
contamination of several ecosystems in different parts of the world (Cisar and
Snyder 2000; Tse et al. 2004). Residues of pesticides have been reported in soil,
water, milk, food, or fish in numerous countries around the world. As these compounds possess high toxicity and constitutes major health and environments issue
(Jaipieam et al. 2009), it is essential to remove them from the environment. Numerous approaches including physical, chemical and biological methods have been
considered for developing decontamination strategies against these chemicals, but
these methods are not considered for large-scale environmental remediation and also
involve harsh conditions (Jacquet et al. 2016). Hence, bioremediation, the treatment
that uses living organisms to transform hazardous substances into lesser or non-toxic
compounds, is an effective way to clean up the soil polluted with chemical pesticides. The first microbe, Flavobacterium sp. that could degrade organophosphorus
compounds was isolated and identified in 1973, and subsequently, several bacterial
and a few fungal species have been isolated which can degrade a wide range of these
compounds in soil systems and liquid cultures. The degradation process of these
compounds takes place through the enzymes organophosphate hydrolase or
phosphotriesterase catalyse encoded by gene opd (organophosphate degrading)
which has been isolated, sequenced, cloned in different organisms and altered for
better activity and stability (McDaniel et al. 1988; Horne et al. 2002).
In recent years, enzymes from extremophiles have emerged as promising alternative to smoothly and quickly decontaminate these chemical compounds. The
phosphotriesterase-like lactonase ScoPox from the archaea Sulfolobus solfataricus
is an attractive candidate for bioremediation. This enzyme has been engineered and
proven to be highly efficient for degrading a number of organophosphorus pesticides
(Elias et al. 2008; Hiblot et al. 2012, 2013; Del Giudice et al. 2016). Two
310
S. Kaushik et al.