A review on the detoxification of organophosphorus compounds by microorganisms

Organophosphorus compounds (OPs) are widely used as pesticides and chemical warfare agents (CWAs). These synthetic compounds reside in the environment and cause serious pollution problems. Organophosphorus compounds can be detoxified rapidly by hydrolysis on exposure to environment, which are liable to be influenced by abiotic and biotic factors. Microorganisms isolated from different niches are the predominant entities in the biosphere with an exceptional ability to metabolize various OPs for their growth. The focus of this work is organophosphorus hydrolase (OPH, E.C. 8.1.3.1), which catalyzes the hydrolysis of many organophosphorus compounds and greatly reduces the toxicity and even can completely mineralize them. Several OPH enzymes, including o-phenylenediamine dihydrochloride (OPD), methyl parathion hydrolase (MPH) mevalonate pyrophosphate decarboxylase (MPD) etc, have been identified which accomplish hydrolysis for specific classes of organophosphorus compounds. The functional gene encoding OPH protein have been cloned, expressed and purified in both prokaryotic and eukaryocyte expression vector. To increase the enzyme activity or enhance their broad-spectrum property, the wild activated OPH was used to modify activated sites by the chemical modification of specific amino acid residues with the use of appropriately designed coenzyme analogs. The applications of the functional strains and OPH enzymes in bioremediation of OPs pollutants included: (i) Bioremediation: the technologies can be generally classified as in situ or ex situ; (ii) immobilization: an immobilized enzyme is the OPH that is attached to an inert, insoluble material such as calcium alginate and agar; immobilized whole cell, the target cell is the functional strains that is capable of degrading special OPs; (iii) construction of genetically engineering bacteria. A versatile genetically engineering bacterium that gained more functional genes from different sources was constructed by gene engineering and enzyme engineering, showing a creative and promising application in OPs detoxification.