Isolation And Degradation Characteristic Of A New Cold-adapted Carbamazepine-degrading Bacterium

Pharmaceutical and Personal Care Products （PPCPs） are the new emergingpollutants and the biodegradation of PPCPs has been the hot and difficult issue inthe field of environmental biology. Carbamazepine is one of the representativesubstances of PPCPs. It has a complex structure and is hard to be degraded bymicroorganism. Therefore, it could not be removed effectively by the traditionalwastewater treatment. Otherwise, low temperature had serious inhibition on themetabolism activity of microorganisms, decreasing the biodegradation efficiency ofPPCPs. The purpose of this dissertation is to solve the problem that themicroorganism had poor biodegradation effect on carbamazepine at low temperature.Microbial pure culture technology was adopted to isolate a cold-adaptedcarbamazepine-degrading bacterium. Moreover, the growth characteristic andbiodegradation mechanism of carbamazepine-degrading bacterium were exploredand the actual treatment effect was validated by the biological activated carbon（BAC） process.Carbamazepine-degrading bacterium, CBZ-4was isolated from the activatedsludge of a Harbin municipal wastewater treatment plant at10oC and carbamazepinewas utilized as the sole sources of carbon and energy. According to themorphological analysis, BIOLOG identification and16S rDNA sequencing, strainCBZ-4was identified as Pseudomonas sp. preliminarily. The optimal growthconditions for CBZ-4were as follows: temparature of10oC，pH of7.0, rotationspeed of150r/min and inoculation volume of13%. After continuous culture for144h, the removal rate of carbamazepine arrived at46.6%by strain CBZ-4. StrainCBZ-4had the certain of biodegradation capability for salicylic acid, phthalic acid,phenol, diphenylamine and estrogen and so on. Futhermore, the biodegradationkinetics of carbamazepine by strain CBZ-4were fitted via the Monod equation.During the biodegradation of carbamazepine at different temperatures, strain CBZ-4had the maximal proportion of42.67%for the unsaturated fatty acids at4oC, whichdemonstrating one of the cold-adapted mechanisms. Strain CBZ-4was accustomedto the effect of low temperature on the biodegradation efficiency by increasing theconcentration of the unsaturated fatty acids in the cell membrane. According to thedetermination and analysis of GC-MS method, the degradation pathways werepresumed elementarily. Carbamazepine was hydrolysed to iminostilbene, and thenoxidated by oxygenase to the small molecules including2-methyl-Phenol, phenoland so on. Finally, the degradation intermediates were mineralized to H₂O and CO₂via TCA cycle. Experiment had shown granule activated carbon had better adsorptioncapability on carbamazepine, fitting to the Freundlich adsorption isotherm. StrainCBZ-4was immobilized on the surface of activated carbon to make the biologicalactivated carbon （BAC） reactor by artificial hanging biofilm. After continuous andsteady operation for26d, the removal rate of COD, NH₄⁺-N and carbamazepineachieved35%,38%and40%above in the BAC reactor, respectively. It was betterthan the treatment efficiency of activated carbon reactor without strain CBZ-4. Theresult illustrated that strain CBZ-4had certain of biodegradation efficiency for theactual wastewater containing carbamazepine.