Genetic Engineering Approach to Toxic Waste Management: Case Study for Organophosphate Waste Treatment

Abstract

Currently, there has been limited use of genetic engineering for waste treatment. In this work, we are developing a procedure for the in situ treatment of toxic organophosphate wastes using the enzyme parathion hydrolase. Since this strategy is based on the use of an enzyme and not viable microorganisms, recombinant DNA technology could be used without the problems associated with releasing genetically altered microorganisms into the environment. The gene coding for parathion hydrolase was cloned into a Streptomyces lividans, and this transformed bacterium was observed to express and excrete this enzyme. Subsequently, fermentation conditions were developed to enhance enzyme production, and this fermentation was scaled-up to the pilot scale. The cell-free culture fluid (i.e., a nonpurified enzyme solution) was observed to be capable of effectively hydrolyzing organophosphate compounds under laboratory and simulated in situ conditions.

Applications of Environmental Biotechnology

“…Toxic organophosphate waste can be treated using the enzyme parathion hydrolase produced and excreted by a recombinant strain of Streptomyces lividans. The cell-free culture fluid contains enzymes that can hydrolyze organophosphate compounds (20). Future applications may involve cytochrome-P450-dependent oxygenase enzymes that are capable of oxidizing different xenobiotics (21).…”

Environmental applications of enzymes

“…Improvements in the useful life of the enzyme, and thereby a reduction in treatment cost, have been accomplished through: selection of an appropriate reactor configuration (Nicell et al, 1993b); the use of additives such as polyethylene glycol to protect the enzyme from premature inactivation (Nakamoto and Machida, 1992); the addition of absorbents such as talc which protect the enzyme from inhibition by reaction products (Arseguel and Baboulène, 1994); and the immobilization of the enzyme on solid supports (Bodzek et al, 1994). In particular, the advantages of immobilization for enzymes can include the preservation of enzyme activity (Coppella et al, 1990), the potential for continuous flow treatment (Caldwell and Raushel, 1991) and the possibility of enzyme reuse (Munnecke, 1977). Thus, this methodology has been pursued during the development of many different types of enzymatic processes, as will be seen below.…”

“…Parathion hydrolase is produced by a number of bacteria including Pseudomonas sp., Flavobacterium sp. and a recombinant Streptomyces (Smith et al, 1982;Coppella et al, 1990). It has been shown to hydrolyze a number of the most widely used organophosphate pesticides such as methyl and ethyl parathion, diazinon, fensulfothion, dursban and coumaphos (Munnecke, 1977;Caldwell and Raushel, 1991).…”

“…These hydrolysis products are much more soluble than the initial substrates and can be treated using ultraviolet light in combination with ozonation. Parathion hydrolase has been shown to successfully hydrolyze coumaphos much more rapidly than chemical hydrolysis and it was further shown to selectively hydrolyze potasan while preserving coumaphos, when specific amounts of enzymes were involved (Coppella et al, 1990). The advantage of this latter process is the prolongation of coumaphos= useful life and the resulting decrease in coumaphos waste generation.…”

Organophosphorus Cholinesterase Inhibitors: Detoxification by Microbial Enzymes

“…The considerable diversity of organophosphate pesticides that parathion hydrolase can utilize as substrates makes it very attractive for use in the detoxification of these materials as has been proposed by a number of groups [16,22,871. However, the relatively low activity observed with DFP and the nerve agents sarin and soman, would indicate that parathion hydrolase is not as well suited for the detoxification of these compounds which are of military interest [27, 721.…”