Detoxification of organophosphate nerve agents by immobilized Escherichia coli with surface-expressed organophosphorus hydrolase

An improved whole-cell technology for detoxifying organophosphate nerve age nts was recently developed based on genetically engineered Escherichia coil with organophosphorus hydrolase anchored on the surface. This article repo rts the immobilization of these novel biocatalysts on nonwoven polypropylen e fabric and their applications in detoxifying contaminated wastewaters. Th e best cell loading (256 mg cell dry weight/g of support or 50 mg cell dry weight/cm(2) of support) and subsequent hydrolysis of organophosphate nerve agents were achieved by immobilizing nongrowing cells in a pH 8, 150 mM ci trate-phosphate buffer supplemented with 1 mM Co2+ for 48 h via simple adso rption, followed by organophosphate hydrolysis in a pH 8, 50 mM citrate-pho sphate buffer supplemented with 0.05 mM Co2+ and 20% methanol at 37 degrees C. In batch operations, the immobilized cells degraded 100% of 0.8 mM para oxon, a model organophosphate nerve agent, in approximately 100 min, at a s pecific rate of 0.160 mM min(-1) m( cell dry wt)(-1). The immobilized cells retained almost 100% activity during the initial six repeated cycles and c lose to 90% activity even after 12 repeated cycles, extending over a period of 19 days without any nutrient supplementation. In addition to paraoxon, other commonly used organophosphates, such as diazinon, coumaphos, and meth ylparathion were hydrolyzed efficiently. The cell immobilization technology developed here paves the way for an efficient, simple, and cost-effective method for detoxification of organophosphate nerve agents. (C) 1999 John Wi ley & Sons, Inc.