Continuous degradation of trichloroethylene by Xanthobacter sp. strain Py2 during growth on propene.

Propene-grown Xanthobacter sp. strain Py2 cells can degrade trichloroethylene (TCE), but the transformation capacity of such cells was limited and depended on both the TCE concentration and the biomass concentration. Toxic metabolites presumably accumulated extracellularly, because the fermentation of glucose by yeast cells was inhibited by TCE degradation products formed by strain Py2. The affinity of the propene monooxygenase for TCE was low, and this allowed strain Py2 to grow on propene in the presence of TCE. During batch growth with propene and TCE, the TCE was not degraded before most of the propene had been consumed. Continuous degradation of TCE in a chemostat culture of strain Py2 growing with propene was observed with TCE concentrations up to 206 microns in the growth medium without washout of the fermentor occurring. At this TCE concentration the specific degradation rate was 1.5 nmol/min/mg of biomass. The total amount of TCE that could be degraded during simultaneous growth on propene depended on the TCE concentration and ranged from 0.03 to 0.34g of TCE per g of biomass. The biomass yield on propene was not affected by the cometabolic degradation of TCE.