Detoxification of the organophosphate nerve agent coumaphos using organophosphorus hydrolase immobilized on cellulose materials

Neurotoxic organophosphates (OPs) are widely used as pesticides and for public health purposes, as well as being nerve gases. As a result of the widespread use of these compounds for agriculture, large volumes of wastewater are generated. Additionally, there are large stockpiles of the nerve gases soman, sarin and VX in the United States and elsewhere around the world. Organophosphorus hydrolase (OPH) is an enzyme that catalyzes the hydrolysis of OP nerve agents. To date, however, the use of this enzyme in detoxification processes has been rather limited due to the high cost of its purification and short catalytic half-life. This paper reports the development of a cost-effective method for the production and immobilization of OPH in a pilot application in an enzyme bioreactor column for detoxification of paraoxon and coumaphos in contaminated wastewaters. A fusion between OPH and a cellulose binding domain that binds selectively to cellulose was generated to allow one-step purification and immobilization of OPH on cheap and abundantly available cellulose immobilization matrices. When packed in a column bioreactor, the immobilized fusion enzyme was able to completely degrade coumaphos up to a concentration of 0.2 mM. However, stirring of OPH immobilized on cellulose materials resulted in complete OP degradation of 1.5 mM coumaphos. The bioreactor column degraded the compounds tested at high concentration, rapidly, and without loss of process productivity for about 2 months.