BIODEGRADATION OF N-PHOSPHONOMETHYLIMINODIACETIC ACID BY MICROORGANISMS FROM INDUSTRIAL ACTIVATED-SLUDGE

A microbial population that biodegraded N-phosphonomethyliminodiacetic acid (PIA), a key component of glyphosate (N-phosphonomethylglycine) process waste, was established. The stoichiometric conversion of PIA t o aminomethylphosphonic acid (AMPA) was observed in a laboratory seque ncing batch reactor (SBR) containing activated sludge from a glyphosat e-manufacturing facility and PIA as sole source of carbon. PIA degrada tion was determined by high-performance liquid chromatography and conf irmed by radiolabeled studies. Greater than 90% of the [carboxymethyl- 2-C-14]-label of PIA was released as (CO2)-C-14 in 7 days using sample s of sludge from the SBR. The cycle time required to biodegrade up to 7.5 mM PIA in SBRs was reduced from 21 to <3 days. PIA biodegradation was also established in an immobilized bacteria column inoculated with mixed liquor from a SBR; >99% PIA removal was achieved at an influent concentration of 2.2 mM and a hydraulic retention time of < 10 h. A p ure bacterial culture was isolated from a SBR by streaking samples of sludge on solid media with PIA as sole carbon source. The isolate was identified as Xanthomonas maltophilia. In liquid culture, X. maltophil ia degraded up to 4.4 mM PIA within 10 days and produced stoichiometri c amounts of AMPA. The results demonstrate the biodegradation of PIA a nd suggest the potential for its treatment in industrial biological tr eatment systems.