Phenolic Compound-Degrading Bacteria In The Coking Wastewater And The Related Degradation Mechanism

Phenols and phenolic compounds are a major source of environmental pollutants, which are very toxic, carcinogenic and mutagenic. More and more phenol wastewater without treatment is threatening the environment seriously with the development of economy. Compared with physical and chemical methods, microorganism biodegradation of phenol wastewater is more effective, lower in cost, and without secondary pollution. Thus, the isolation and identification of phenol-degrading bacteria are very important, especially in promoting the phenol sewage treat process.Together,26possible phenol-degrading bacteria were isolated from the activated sludge through LB、216L and phenol, m-cresol inorganic salt medium. Two other degrading bacteria named AEJ1and ANJ3were obtained by enrichment with gradual increase of m-cresol dosage as the sole source of carbon. Strain AEJ1was able to metabolize94.6%m-cresol with initial concentration790.77mg/L in just48h; while ANJ3metabolized92.2%m-cresol with initial concentration762.75mg/L in48h.Analysis of16S rRNA gene sequence showed that the isolates belonged to28different strains of28species of20genera. Most of them belonged to β-and y-Proteobacteria. Four of them possibly belonged to novel species based on their low16S rDNA sequence similarity to the described type strains. Results of systematic classification and identification of strain AN3showed that it represents a novel species in the genus Ottowia, of which the name Ottowia beijingensis sp. nov. is proposed. Results of systematic classification and identification of strain AE31showed that it represents a novel species in the genus Pedobacter, of which the name Pedobacter beijingensis sp. nov. is proposed.PCR analyses revealed the encoding genes of phenol hydroxylase, the nucleotide sequence of PCR fragment from strain AE14shared99%homology with the phenol hydroxylase of strain Pseudomonas mendocina PC3, and AN3shares100%homology with the phenol hydroxylase of phenol-degrading strain Diaphorobacter sp. J5-51, while AEJ1and ANJ3both shares99%homology with the phenol hydroxylase of strain Pseudomonas putida KL33. The existence of the key enzymes further confirmed the phenol-degrading capability at molecular level.Whole genome sequencing of strain AN3with phenolic degradation effect and preliminary analysis of the genome was carried out. Lots of phenol and m-cresol degradation genes were found, including13genes (orf1610to orf1642) which may be involved in phenol degradation meta-cleavage pathway. Meta-cleavage pathway for phenol degradation in strain AN3T was proposed, while maybe there are two independen pathways for m-cresol degradation.In summary, lots of phenol and m-cresol degrading bacteria were isolated fron activated sludge, and of practical application. Particularly, strain AEJ1and ANJ3ar excellent phenol and m-cresol degrader, and need further study.