VX. Direct biological treatment of mustard is not possible. Enzyme-based processes for both GB and VX would have to be available for practical application to the stockpile configuration. Currently, proof of concept has been demonstrated only for GB. Engineering development appears premature. Biological treatment of reaction products from chemical agents, including GB VX, and mustard, appears however to have a reasonable chance for early application.

DIRECT BIOLOGICAL TREATMENT OF CHEMICAL AGENTS

Mustard

Mustard (H, HD, HT) is a strong vesicant and DNA mutagen that destroys cellular membranes and enzymes. Development of a biological process for direct treatment of mustard agents is extremely unlikely because of their generic xenobiotic characteristics. No recent information has been reported on biological processes for direct destruction of mustard agents.

GB and VX

Several enzyme systems have been reported that are capable of degrading GB and other neurotoxic fluorophosphonates to varying extents and at differing rates (NRC, 1993a). The initial enzyme-catalyzed hydrolysis of GB results in the production of hydrogen fluoride and monoisopropyl methylphosphonate. In addition, several enzyme and cellular systems have been identified that are capable of cleaving the P—C bond; however, their direct applicability to GB or VX destruction has not been evaluated. At the time of the Alternatives report, critical limitations of enzyme systems to date were (1) tentative reported results indicating enzyme degradation activity on VX, (2) the absence of reaction rate data, and (3) lack of demonstration of proof of principle for practical process and reactor designs based on the reported enzyme systems. However, recent enzyme characterization and laboratory development of treatment processes based on specific enzyme systems have been initiated and several positive results reported.

It has been reported that hydrolysis of VX with specific P—S bond hydrolysis was observed with the organophosphorus hydrolase (OPH) enzyme from soil bacteria (Harvey et al., 1993b; Kolakowski et al., 1993). The specific activity of the OPH enzyme in studies at Edgewood Research, Development and Engineering Center (ERDEC), Aberdeen, Maryland, on VX was between 0.5 and 1.0 µmol VX hydrolyzed per minute per milligram of protein.



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