Organophosphates are esters of phosphoric acid and can be hydrolyzed and detoxified by carboxylesterase and phosphotriesterase. In this work esterase enzyme (Est5S) was expressed in yeast to demonstrate the organophosphorus hydrolytic activity from a metagenomic library of cow rumen bacteria. The esterase gene (est5S) is 1098 bp in length, encoding a protein of 366 amino acid residues with a molecular weight of 40 kDa. Est5S enzyme was successfully produced by Pichia pastoris at a high expression level of approximately 4.0 g L-1. With p-nitrophenol butyrate as the substrate, the optimal temperature and pH for enzyme activity were determined to be 40 C and pH 7.0, respectively. The esterase enzyme was tested for degradation of chlorpyrifos (CP). TLC results obtained inferred that CP could be degraded by esterase enzyme (Est5S) and HPLC results revealed that CP could be efficiently degraded up to 100 ppm. Cadusafos (CS), coumaphos (CM), diazinon (DZ) dyfonate (DF), ethoprophos (EP), fenamiphos (FM), methylparathion (MPT), and parathion (PT) were also degraded up to 68, 60, 80, 40, 45, 60, 95, and 100%, respectively, when used as a substrate with Est5S protein. The results highlight the potential use of this enzyme in the cleanup of contaminated insecticides.
Title: Nematicidal efficacy of MCW-2, a new nematicide of the fluoroalkenyl group, against the root-knot nematode Meloidogyne javanica Oka Y, Shuker S, Tkachi N Ref: Pest Manag Sci, 65:1082, 2009 : PubMed
BACKGROUND:
The small number of available nematicides and restrictions on the use of non-fumigant nematicides owing to high toxicity to human and non-target organisms hinder effective nematode control. The nematicidal efficacy of MCW-2, a new nematicide of the fluoroalkenyl group, was evaluated against the root-knot nematode Meloidogyne javanica (Treub.) Chitwood.
RESULTS:
MCW-2 showed irreversible nematicidal activity against second-stage juveniles of M. javanica in vitro, following exposure for 48 h at concentrations as low as 0.5 mg L(-1), in contrast to fenamiphos or cadusafos. When exposed to MCW-2 for shorter periods, motile juveniles became immobile with time after rinsing in water. MCW-2 at 8 mg L(-1) inhibited nematode hatching, which, however, recovered after rinsing in water. In pot and plot experiments, 0.5 mg MCW-2 L(-1) soil and 2 kg MCW-2 ha(-1), respectively, controlled M. javanica similarly to or better than fenamiphos or cadusafos at the same concentrations or at their recommended doses. In the soil, the nematicidal activity of MCW-2 was less persistent than that of fenamiphos.
CONCLUSION:
MCW-2 has potential to be used as a new non-fumigant nematicide that probably has a novel mode of action.
BACKGROUND:
In intensive agriculture, the use of pesticides and soil fumigants is necessary to produce economically viable crops worldwide. However, this practice may involve undesirable effects on human health and the environment. In 1995, methyl bromide was restricted by the Montreal Protocol because of possible ozone depletion. The objective of this study was to compare intrinsic environmental and toxicological properties of 11 active substances with nematicidal properties, some of them recognized as methyl bromide alternatives.
RESULTS:
Four groups of active substances were discriminated by a series of principal component analyses (PCAs): (a) high toxicity to non-target fauna, humans and animals and medium persistence in the environment (cadusafos, ethoprophos and fenamiphos); (b) high toxicity to humans, animals and non-target fauna and high persistence (carbofuran and fosthiazate); (c) low toxicity to non-target fauna, humans and animals and low persistence (carbosulfan, benfuracarb and oxamyl); (d) low toxicity to humans, animals and non-target fauna and medium persistence in the environment (1,3-dichloropropene, chloropicrin and methyl bromide).
CONCLUSION:
Evaluating the multiple aspects of toxicological and environmental properties of active substances through PCA is proposed as a helpful tool for initially comparing the complex toxicological behaviour of active substances as plant protection products.
