Detoxification of organophosphate nerve agents by immobilized dual functional biocatalysts in a cellulose hollow fiber bioreactor

A whole-cell technology for detoxification of organophosphates based on genetically engineered Escherichia coli cell expressing both cellulose-binding domain (CBD) and organophosphorus hydrolase (OPH) onto cell surface was reported recently (Wang et al., [2002]). This study reports the application of these biocatalysts when immobilized in a cellulose hollow fiber bioreactor (HFB) for the biodetoxification of a model organophosphate, paraoxon, in a continuous flow mode. In 24 h, 0.79 mg wet cell/cm2 fiber surface were immobilized onto cellulose fibers specifically and strongly through the cellulose binding domain, forming a monolayer demonstrated by Scanning Electronic Micrograph, and essentially no cell was washed away by washing buffer. The immobilized biocatalyst had a high performance of detoxifying paraoxon solution of 5,220 micromol/h·L reactor or 990 micromol/h·m2 reactor. The immobilized biocatalysts maintained a stable degradation capacity for 15 uses over a period of 48 days with only 10% decline in degradation efficiency under operating and storage conditions. In addition, the bioreactor was easily regenerated by washing with 1% sodium dodecyl sulfate (SDS), with 86.7% immobilization capacity and 93.9% degradation efficiency recovery. This is the first report using the HFB in a non-traditional way, immobilizing whole-cell biocatalysts by specific adhesion thus rendering the catalysis operation the advantages of low pressure drop, low shear force, and low energy requirement. The successful application of this genetically engineered dual functional E. coli strain in a model bioreactor shows its promise in large-scale detoxification of organophosphate nerve agents in bulk liquid phase.