Isolation And Identification Of A Pyromellitic Acid(PMA) Degrading Strain PB-3 And Its Degradation Characteristics And Pathway

Pyromellitic acid(PMA)is one of the most widely used aromatic carboxylic acid compounds,playing an important role in the chemical synthesis and polymer industries.High concentrations of PMA in wastewater will cause great difficulties in sewage treatment and bring great harm to the natural environment because of its poor biodegradability,high COD,low pH and other characteristics.In this study,a highly-effective PMA-degrading bacteria,PB-3,which could utilize PMA as the sole source of carbon and energy for growth was successfully isolated from activated sludge.According to the 16S rRNA gene sequence analysis,combing with its physiological and biochemical properties,the strain was identified as Arthrobacter phenanthrenivorans.The stain PB-3 growed well when it was cultured in LB liquid medium.4 hrs later,bacteria entered into the logarithmic growth period and continued for 20 hrs and then,bacteria entered into stable growth period.The optimum temperature for the growth of strain PB-3 was 30 ?,the optimal pH was 7.0.Larger amount of dissolved oxygen in water was benefit for the bacteria growth.When the concentration of NaCl was more than 10 g/L,the growth of strains was inhibited.For different carbon sources,the strain could utilize glucose and sucrose but lactose.For various nitrogen sources,the strain could highly utilize peptone and was followed by ammonium chloride,potassium nitrate,ammonium sulfate and urea.The strain was resistant to norfloxacin,but sensitive to tetracycline,gentamicin,kanamycin,chloramphenicol,ceftriaxone,penicillin,ofloxacin,carbenicillin,ampicillin,spectinomycin and streptomycin.The strain PB-3 could use PMA as the sole carbon source for growth and could completely degrade 400 mg/L PMA in 64h.The optimum temperature and pH for PMA degradation by strain PB-3 were 30? and 7.0,respectively.When the initial PMA concentration was increased from 200 mg/L to 1000 mg/L,the degradation efficiency has no significant decrease.The degrading rate showed a positive correlation with the initial inoculum proportion.The increased NaCl concentration will inhibit the PMA degradation.Glucose does not accelerate the degradation rate of PMA.PB-3 can degrade 1,2,4-benzene tricarboxylic acid,phthalic acid and isophthalic acid,but trimesic acid.The relationship between the concentration of PMA and biodegradation rate of strain PB-3 can be described by the Monod equation as V=47.6S/(181+S).During the degradation of PMA,three metabolites,1,2,4-benzenetricarboxylic acid,terephthalic acid and 2,5-dihydroxyterephthalic acid were identified based on liquid chromatography-mass spectrometry analysis.