Study On The Degradation Mechanism Of Benzene Compounds By Marine Petroleum Hydrocarbon Degrading Bacteria Acinetobacter

With the rapid development of the economy,organic aromatic hydrocarbon pollutants discharged from industrial wastewater have seriously affected human health.Catechol and benzoic acid are two intermediate metabolites in the metabolism of benzene compounds,and are also common environment pollutants in industry wastewater.Nonylphenol(NP)as an environmental endocrine disruptor,can be enriched by food chain and eventually threaten marine life health.So we have to remove these environment pollutants immediately.However,there were few studies on the metabolomics of benzene pollutants by strains.The metabolic response of the strain to nonylphenol was important for environment repair.In this paper,the degradation characteristics of catechol and sodium benzoate by the strain which had a capability of highly effective degrading aromatic compounds were studied.The maximum tolerated concentration of the strain Tust-DM21 on catechol was 700 mg/L.The optimum conditions for the strain to degrade 600 mg/L of catechol were as follows:5%of inoculumvalue,pH 6.0 and temperature 35?,respectively.Under the optimal condition,the degradation rate of catechol could reach 92%.The maximum tolerated concentration of the strain on sodium benzoate was 4 500 mg/L.The optimum conditions for the strain to degrade 1 500 mg/L of sodium benzoate were as follows:3%of inoculum value,pH 8.0 and temperature 35?,respectively.Under the optimal condition,the degradation rate of sodium benzoate could reach 95%.In addition,the crude enzyme characteristics of catechol 1,2-dioxygenase(C12O)in the strain showed that the C12O enzyme catalyzed the ortho-ring opening of the benzene ring to achieve catechol degradation.The optimal conditions for the enzymatic reaction of C12O were as follows:pH 8.0 and temperature 35?.The crude enzyme kinetic parameters of C12O were as follows:Km=25.68 mol/L,Vmax=0.13 mol/(mL·min).In addition,the enzyme activity of benzoic acid 1,2-dioxygenase was measured,and the enzyme activity of benzoic acid 1,2-dioxygenase was 3.53 U.The degradation characteristics of NP by the strain were studied.The maximum tolerated concentration of the strain Tust-DM21 on NP was 150 mg/L.The optimum conditions for the strain to degrade 90 mg/L NP were as follows:pH 8.0,temperature 35?,70 mg/L glucose concentration.When the glucose concentration was 70 mg/L,the strain had the best degradation effect on nonylphenol with a degradation rate of 73.9%.Then orthogonal experiments results that showed the optimal conditions for removing NP were as follows:NP concentration had the greatest effect on NP degradation by strain,then followed by temperature,glucose concentration and pH.When the NP concentration was 90 mg/L,pH 8.0,temperature 35?,and glucose concentration 30 mg/L,the NP degradation rate by the strain could reach 81.2%.Under the same treatment time,NP degradation rate could increase 7.3%.Using metabolomics technology,the metabolic mechanism of NP was studied.The results showed as fllows:a total of 178 differential metabolites were detected by HPLC-MS.There were 24 significantly up-regulated metabolites and 154 down-regulated metabolites.Most of differential metabolites were aromatic compounds and lipid compounds,and the rest were organic oxygen compounds,organic nitrogen compounds and ketone compounds.The KEGG metabolic pathway analysis of these differential metabolites showed as follows:most of the metabolic pathways of differential metabolites were fatty acid biosynthesis,amino acid metabolism,aromatic compound degradation,and secondary metabolite biosynthesis.Finally we screened 9 metabolites which were related to the NP degradation pathway.So nonylphenol degradation pathway of this strain started from the nonylphenol alkyl chain end within a cycle of hydroxylation,subsequent and decarboxylation.Acinetobacter sp.Tust-DM21 as a petroleum-degrading strain could highly degrade catechol,sodium benzoate and NP.The results showed that the Tust-DM21 strain had a good application prospect for removing these pollutants.The application of metabolomics technology provided a theoretical basis for the study of stain metabolic regulation to NP.