Characterization of dibenzofuran biodegradation by a bacterial consortium DBFC

Abstract:

[Objective] Dibenzofuran (DBF) is a highly toxic compounds and widely spread in environment, used as a model compound in studying the microbial degradation of polycyclic aromatic compounds. [Methods] A bacterial consortium DBFC was isolated from petroleum contaminated soil in Liao River China. The total DNA was extracted to analyze the biodiversity of DBFC, and the strain was isolated and purified by plate dilution coating method. The optimum growth conditions of mixed bacteria were studied through measuring the absorption value of OD₆₀₀. The effects of substrate concentration, substrate, adding nutrient and surface-active substance on the degradation efficiency were studied under the optimum growth conditions. The intermediate metabolites of DBF degradation were detected by ultra-high resolution mass spectrometry, and the metabolic pathway was speculated. [Results] Microbial diversity analysis showed 84.06% of the strains identified in DBFC were Paenibacillus sp., 8.17% were Achromobacter sp., 0.77% were Pseudmononas sp., other strains contain only 2.13%. Four strains, belong to Ochrobactrum sp., Achromobacter sp., Stenotrophomonas sp. and Microbacterium sp., were isolated. Through cultivated in mineral-NH₄Cl salt medium adding DBF as the carbon source, the four stains could not grow. The optimal growth temperature and pH value was 30℃ and 8.0, respectively. Under optimal conditions, DBFC could completely degrade up to 1000 g/L of DBF in 8 days. The maximum degradation rate of DBFC was 0.031 mmol/(L·h) under 1.0 g/L of DBF. Adding glucose, yeast and peptone, the degradation rate of DBF were increased by 1.38, 1.14, and 1.24 fold, respectively. Adding sodium dodecyl sulfonate and Triton-X-100, the degradation rate were inhibited; while adding Tween-80, the degradation rate was decreased. Metabolites 2,2',3-trihydroxybiphenyl, 2,4-hexadienoic acid, gentisic acid and salicylic acid were identified by ultra-high performance liquid chromatography (UPLC). The bacterial consortium DBFC could also use gentisic acid and salicylic acid as sole carbon and energy source, which were respondence with the previous results. [Conclusion] The bacterial consortium DBFC had high efficient in degrading of DBF under pH 8.0 condition, which could be further exploited in situ remediation of polycyclic aromatic compounds contaminated sites. Through UPLC-MS/MS analysis, the metabolites were identified, which provides methods and directions for the study of metabolic process of the polycyclic aromatic compounds.