Optimization of the Use of His₆-OPH-Based Enzymatic Biocatalysts for the Destruction of Chlorpyrifos in Soil.

Olga Senko,Olga Maslova,Elena Efremenko

doi:10.3390/ijerph14121438

Abstract

Applying enzymatic biocatalysts based on hexahistidine-containing organophosphorus hydrolase (His6-OPH) is suggested for the decomposition of chlorpyrifos, which is actively used in agriculture in many countries. The application conditions were optimized and the following techniques was suggested to ensure the highest efficiency of the enzyme: first, the soil is alkalinized with hydrated calcitic lime Ca(OH)2, then the enzyme is introduced into the soil at a concentration of 1000 U/kg soil. Non-equilibrium low temperature plasma (NELTP)-modified zeolite is used for immobilization of the relatively inexpensive polyelectrolyte complexes containing the enzyme His6-OPH and a polyanionic polymer: poly-l-glutamic acid (PLE50) or poly-l-aspartic acid (PLD50). The soil’s humidity is then increased up to 60–80%, the top layer (10–30 cm) of soil is thoroughly stirred, and then exposed for 48–72 h. The suggested approach ensures 100% destruction of the pesticide within 72 h in soils containing as much as 100 mg/kg of chlorpyrifos. It was concluded that using this type of His6-OPH-based enzyme chemical can be the best approach for soils with relatively low humus concentrations, such as sandy and loam-sandy chestnut soils, as well as types of soil with increased alkalinity (pH 8.0–8.4). Such soils are often encountered in desert, desert-steppe, foothills, and subtropical regions where chlorpyrifos is actively used.

Highlights

The ever-continuing growth of the Earth’s population is accompanied with an increasing demand for agricultural products: fruit, vegetables, cereals, meat, etc
The trend towards higher economical efficiency has led to the widespread utilization of organophosphorus and organochlorine agricultural pesticides as an inevitable part of modern agricultural practices
Special attention was paid to the possibility of achieving the soil pH of 8.0–8.4 and keeping it in that range, as well as to the influence of the alkalizing agent on the stability of the enzymatic hydrolyzing activity towards organophosphorus pesticides

Summary

Introduction

The ever-continuing growth of the Earth’s population is accompanied with an increasing demand for agricultural products: fruit, vegetables, cereals, meat, etc. Development of animal husbandry and plant cultivation implies an increase of the areas used for grazing and hay harvesting as well as expansion of arable land and quick deforestation of territories [3,4,5]. Since most areas with humus-rich soils are already being used in agricultural processes, such development calls for increasing use of steppes and deserts, which heretofore have been largely usused. The trend towards higher economical efficiency has led to the widespread utilization of organophosphorus and organochlorine agricultural pesticides as an inevitable part of modern agricultural practices. The application of pesticides against various plant pests is currently well founded from the economical viewpoint [7,8,9,10].

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Conclusion