Kinetic Study of Trichloroethylene Biodegradation by Methylosinus trichosporium OB3b PP358 lmmobilized in a Fibrous-Bed Bioreactor

Abstract

Biodegradation of trichloroethylene (TCE) by resting cells of methanotrophic Methylosinus trichosporium OB3b PP358, which constitutively expresses soluble methane monooxygenase (sMMO), was studied in a fibrous-bed bioreactor operated in the recycle batch mode. Cells were grown on methane as the substrate with aeration, and then used to degrade TCE through the cometabolism with sMMO in the absence of methane. Complete biodegradation of TCE was verified with the TCE and chloride ion mass balance. In general, concentration of up to ~12 mg/l, and followed the first-order reaction kinetics. TCE transformation was inhibited in the presence of methane or methanol. Without the energy source and after being exposed to TCE for an extended period, cells gradually lost most of their capability in degrading TCE, which was attributed to reduced sMMO enzyme activity due to lack of NADH and cell death caused by TCE toxicity and oxygen starvation. However, the reactor was able to recover its TCE degradation ability after rejuvenating and regrowing cells with methane and air. Compared to free cell and other immobilized cell systems, the cells immobilized in the fibrous-bed bioreactor not only showed a much higher TCE degradation rate (up to 84.77 mg/(1 day) or ~32 times of that from free cells), but also had a better tolerance to TCE (22.6 mg/l or ~11 times higher than that with free cells). With periodical rejuvenation, the bioreactor could be used for long-term treatment of TCE-contaminated water.