Isolation And Characterization Of A Dichloromethane-Degrading Strain And The Optimization Of Degradation Condition

A strain H13which could utilize dichloromethane (DCM) as the sole carbon and energy source was isolated from the activated sludge of a pharmaceutical factory in Taizhou. Based on the analysis of the morphological, cellular fatty acid profile, physiological and biochemical characteristics and16S rDNA sequence, strain H13was identified as Methylobacterium rhodesianum, and was deposited in China Center for Type Culture Collection(CCTCC NO:M2010121). To date, DCM degradation by Methylobacterium rhodesianum have not been reported in any other literature.This thesis studied the effects of nitrogen source, oxygen supply conditions, substrate concentration and others factors to ability of degrading DCM by M. rhodesianumH13. We found the main factors which influence dichloromethane-degrading strain from nine factors via the Plackett-Burman experiment, such as temperature, pH, Na2HPO4·12H2O and (NH4)2SO4. Base on this experiment, the optimal cultivating conditions of M. rhodesianumH13strain were chosen by Response surface methodology. The results showed that the optimum conditions were as followd:Na2HPO4·12H2O was4.5g, was0.5g, pH was7.55and temperature was33.73℃. After this condition of cultivating was chosen, the specific degradation rate to DCM was increased from0.1282h-1to0.1625h-1. The concentration of DCM was4.9mM, and could be degraded completely and the release of Cl-was9.4mM. The M.rhodesianumH13strain would be suppressed significantly when the concentration of dichloromethane was up to30mM, however, the degradation concentration of DCM could be higher than before when a silicone oil-water two phase system was formed by adding silicone oil into the inorganic salt culture medium. At the same time, the biodegrading rate to dichloromethane was also increased.In this thesis, the scale-up cultivation antecedent conditions of microorganism cell and preparation of the solid inoculants were also studied. We find DL-malic acid was the good carbon source to the strain scale-up cultivation. The best cultivating concentration and time respectively was4g/L and36h. Peat was used as carriers to make solid inoculants and the storage effect of solid inoculants was good after its function was researched.