Microbial degradation of N,N-dimethylformamide by Paracoccus sp strain DMF-3 from activated sludge

N,N-dimethylformamide (DMF) was a typical toxic chemical and existed extensively in industrial wastewater. In this study, a strain of the high-efficient DMF degrading bacteria DMF-3 belonging to Paracoccus sp. was enriched and isolated from activated sludge. The removal rate of DMF by DMF-3 was up to 100% while 1000 mg/L DMF was used as the sole carbon and nitrogen source. Growth kinetics model of DMF-3 was thus established, and the kinetic constants were determined with maximum specific growth rate mu(max) = 0.22 (h(-1)), saturation constant Ks = 0.41 (g/L) and inhibition constant Ki = 25.93 (g/L). Based on the analysis of the intermediate products, it was found that DMF was firstly converted into dimethylamine and formic acid, and these intermediates were finally degraded to ammonia and carbon dioxide following the typical metabolic pathway of methylotrophs. In addition, to enhance the degrading capacity of DMF-3 in high DMF concentration, ultraviolet mutagenesis process was applied. Compared with the usage of the original strain of DMF-3, the degradation rate was increased by 14.8% with the usage of obtained mutant strain with applied initial DMF concentration 10,000 mg/L.