Aerobic biodegradation of trichloromethane by Stenotrophomonas sp. GYH and its biodegradation mechanism analysis

A new strain, Stenotrophomonas maltophilia GYH, used trichloromethane (TCM) as the only carbon source for its growth was isolated. This strain was the first reported bacterium with TCM aerobic degradation ability. The initial TCM concentration of 8.93 mg·L-1 resulted in a degradation efficiency of 100% and a mineralization efficiency of 52% under the role of the strain. Based on the carbon balance and chlorine balance, the strain GYH could convert about 40 μg organic C contained by TCM to 20.4 μg inorganic C and 19.4 μg C by biomass, along with the complete dechlorination of TCM in 84 h. The maximum specific growth and biodegradation rates were 0.078 and 0.018 h-1, respectively. Two TCM-degrading genes were cloned and successfully expressed in the constructed strains, with 66.45% and 23.61% dechlorination efficiency. In combination with gas and ion chromatography detection and genetic analysis, an aerobic biodegradation pathway of TCM was proposed. TCM was finally converted to CO2, Cl-, and biomass under the aerobic degradation of the GYH. Such results supply fundamental knowledge for future research to effectively explain the molecular mechanism of TCM aerobic biodegradation and expand the potential industrial application of TCM biodegradation in polluted environments.