Isolation, Identification And Degradation Characterization Of DMAC-Degrading Bacterial

A bacterial strain, capable of utilizing DMAC as sole carbon and nitrogen source was isolated from activated sludge collected from wastewater treating pool of a pesticide company. This strain was identified asPseudomonas sp.. according to its morphological, physiological and biochemical analysis and the analysis of its16S rRNA gene sequence, and named DM5.The optimal growth temperature and pH of DM5were30℃and7.0respectively. The strain could still grow at low temperature, but high temperature could inhibit the growth of strain; The strain could grow at pH5.0-9.0.The liquid volume in flask showed a negative correlation with the growth of DM5. Strain could grow well in the NaCl solution with the concentration of0-30g/l, and the optimum concentration of NaCl was5g/l.DM5could utilize glucose, fructose, xylose as carbon source; peptone urea ammonium nitrate as nitrogen source; DM5was sensitive to gentamicin and kanamycin.Strain DM5could degrade100mg/l DMAC within48h. The optimal pH and temperature for the degradation were7.0and30℃, respectively. The degrading rate showed a negative correlation with the liquid volume in flask and a positive correlation with the inoculum size. Addition of Fe3+and Mg2+promote the degradation of DMAC while Cd2+and Ag+inhibited the degradation. Ba2+、Zn2+、Al3+、Cu2+had little impact on the degradation. Addition of either SO42-or NH4+reduced the degradation efficiency of DMAC to a certain extent. The inhibition became significant when the concentration of SO42-and NH4+reached600mg/L and1100mg/L respectively.Used sodium alginate embedding the DMAC degrading strain DM5, results showed that mechanical strength of immobilized beads best and the degradation of DMAC effect was best when the concentration of sodium alginate was4%, the concentration of CaCl2was3%, encap sulated cell mass was6g/L and immobilized time was4h.Immobilized bacteria could tolerance pH and temperature in a wider range. The immobilized DM5cells were taken to treat the DMAC wastewater with fluidized-bed as the reactor. The optimum amount of imbedded balls was:imbedded ball/wastewater=90/1000. The concentration of DMAC had great impact on the removal efficiency. After four consecutive degradation experiments, immobilized degrading bacteria could keep high stability and reactivity.