| Polycyclic aromatic hydrocarbons?PAHs?constitute a group of typical and representative of persistent organic pollutants for soil contamination.Due to their carcinogenic,teratogenic and mutagenic properties,PAHs pose serious harm to human health and ecological environment.Bioremediation of PAHs pollution is a research hotspot for experts at home and abroad.Bioremediation of PAHs is the most promising technology,because this method is economic and efficient.Therefore,the study of the interaction between PAHs and microorganisms has great significance for bioremediation PAHs pollution.Ochrobactrum anthropi Na-B was isolated from creosote-contaminated soil,and studied for the physicochemical properties of the cell surface.The characteristics of the adsorption,biodegradation of naphthalene and phenanthrene by this strain was studied.While a numerical model and thermodynamic electron equivalents model were used to simulate phenanthrene degradation.Results of the study are as follows:1.There are four distinct proton binding sites of this strain,with pKa values in the rang of 2.31-4.70?pK1?,5.03-6.37?pK2?,6.83-7.75?pK3?and 8.81-9.69?pK4?,corresponding to phosphoric/carboxylic,carboxylic,phosphoryl,and hydroxyl/amine groups,respectively.The total site concentration was 4.21×10-5-2.27×10-4 mol/g.When the C:N ratio was 6:1 and bacteria was at stationary phase,the concentration of the four sites was?1.04±0.48?×10-4 mol/g,?3.04±1.20?×10-5 mol/g,?2.45±0.44?×10-5 mol/g and?6.75±1.95?×10-5 mol/g,respectively.Microbial growth with ammonium as nitrogen source was significantly more than with nitrate as nitrogen source,but the p Ka was lower.2.Biosorption capacity for naphthalene and phenanthrene was relatively higher when bacteria was in the stationary phase.The maximum adsorption capacity was achieved at pH=7.0,which was 5.42 mg/g and 5.97 mg/g for naphthalene and phenanthrene,respectively.The adsorption equilibrium time was 30 and 180 min for naphthalene and phenanthrene,respectively.The adsorption kinetics fit well with the pseudo-second-order kinetic model.The Freundlich model and two-site Langmuir model exhibited a better fit to the biosorption data.The changes of enthalpy indicates that the biosorption process was exothermic.There are competitive effect of naphthalene and phenanthrene.Phenanthrene will promote biosorption of naphthalene,while naphthalene inhibits biosorption of phenanthrene.The competition factor?CF?was 1.07-1.59 for naphthalene while the competition factor was 0.44-0.95 for phenanthrene.Adsorption capacity of naphthalene and phenanthrene increased with the increasing of ion valence.3.The degradation efficiency for naphthalene biodegradation was reached 100%at pH 7.2,30.7?,inoculum size 3.0%.While the degradation efficiency for phenanthrene biodegradation was reached 85%at pH 7.5,28.6?,inoculum size 4.6%.The degradation pathways of naphthalene main via gentisate pathway,but there also exist phthalic acid pathway.Phenanthrene degradation mainly through salicylic acid pathway.4.In mixture,the main effect of naphthalene,phenanthrene,pyrene concentration and the interaction between naphthalene and pyrene on phenanthrene degradation were found significant.In addition,pyrene removal were significantly affected by the three-way interaction of naphthalene,phenanthrene,pyrene and two-way interactions between the three substrates.The removal efficiency of pyrene increases with increasing of the concentration of naphthalene and phenanthrene.Varies of initial concentration of phenanthrene and pyrene have little effect on the removal of naphthalene,naphthalene removal efficiency was remained at about 98%.5.Due to the poor solubility of phenanthrene at room temperature,a numerical model which coupled substrate dissolution,metabolism and microbial growth kinetics was used to simulated phenanthrene metabolism by Ochrobactrum anthropi Na-B.The correlation coefficient?R2?of the model was in range of 0.346 to 0.975.The no-growth concentration calculated by the model was 0.053 mg/L.The maximum specific degradation rate was 1.233 g phenanthrene/g bacteria d and true yield was0.139 g bacteria/g phenanthrene for Ochrobactrum anthropi Na-B.While the yield calculated by thermodynamic electron equivalents model were 0.73 g bacteria/g phenanthrene. |
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