Effective utilization of dichloromethane by a newly isolated strain Methylobacterium rhodesianum H13

An effective dichloromethane (DCM) utilizer Methylobacterium rhodesianum H13 was isolated from activated sludge. A response surface methodology was conducted, and the optimal conditions were found to be 4.5 g/L Na2HPO4·12H2O, 0.5 g/L (NH4)2SO4, an initial pH of 7.55, and a temperature of 33.7 °C. The specific growth rate of 0.25 h(-1) on 10 mM DCM was achieved, demonstrating that M. rhodesianum H13 was superior to the other microorganisms in previous investigations of DCM utilization. DCM mineralization paralleled the production of cells, CO2, and water-soluble metabolites, as well as the release of Cl(-), whereas the carbon distribution and Cl(-) yield varied with DCM concentrations. The facts that complete degradation only occurred with DCM concentrations below 15 mM and repetitive degradation of 5 mM DCM could proceed for only three cycles were ascribed to pH decrease (from 7.55 to 3.02) though a buffer system was employed.