The Two Fluorene Degrading Isolation And Identification Of Bacteria And Degradation Characteristics

Two predominant fluorene-degrading strains(named W-1 and W-2 , respectively)which can use fluorene as sole carbon and energy source for growth in the selective culture medium was isolated and screened from activated sludge of a coking plant. On the basis of morphological observation and physio-biochemical test, the strain W-1 and W-2 were identified as Alcaligenes faecalis and Stenotrophomonas acidaminiphila by 16S rDNA gene sequence and phylogeny analysis, respectively. Under the conditions of inoculation amount 10% (V/V), initial concentration of fluorene 40 mg/L, pH 7.0 and temperature 30℃, the degradation efficiency of fluorene by the strain W-1 and W-2 reached 87.8% and 86.0% within 11 days, respectively.The results indicate that fluorene degradation ability would be increased greatly when the strain W-1 and W-2 were cultivated together, and the degradation efficiency of fluorine reached 94.0%, in the same conditions.Alkaline and boiling lysis methods were applied to extract plasmids from strain W-2, but none of plasmids were detected.It was supposed that fluorene-degrading gene harbored by strain W-2 may locate on the chromosomes instead of on the plasmids.The degradable PAHs as substrates for metabolism of the strains are diversiform. In the cultivation system solely containing chrysene, pyrene, anthracene or phenanthrene of 20 mg/L, the degradation efficiency of chrysene, pyrene, anthracene and phenanthrene by the strain W-1 reached 95.5%,71.0%,85.7% and 80.0%, respectively, and the degradation efficiency of chrysene, pyrene, anthracene and phenanthrene by the strain W-2 reached 86.0%,80.2%,91.4% and 94.5%, respectively . The results showed that the strains could be used as superordinary microorganism resource to remedy environment complexly polluted by polycyclic aromatic hydrocarbons.The effect of initial concentration of fluorene in culture solutions, strains dosage and pH on biodegradation efficiencies was also inspected. The enhancement of exotic carbon sources (such as glucose, phthalic acid, salicylic acid, pyrocatechol, naphthalene) on biodegradation of fluorene was studied.The results show that the strains dosage, initial concentration of fluorene and pH has obvious influence on the biodegradation. The appropriate condition for degradation of fluorene by the strain W-1 is: initial concentration of fluorene, 10 mg/L~40 mg/L; strains dosage, 7%~25%; pH, 7.0~9.0. The appropriate condition for degradation of fluorene by strain W-2 is: initial concentration of fluorene, 10 mg/L~40 mg/L; strains dosage, 7%~20%; pH, 6.0~7.0.The difference of impact of exotic carbon sources on biodegradation of fluorene by the strain W-1 and W-2. Eligible addition of glucose, salicylic acid, pyrocatechol and PAH naphthalene to the reaction system can all stimulate the biodegradation of fluorene by strain W-2.The removal rate of fluorene reached 93.8%,97.3%,97.4% and 96.5%, by the strain W-1, respectively, when 100mg/L glucose, 50mg/L salicylic acid, 50mg/L pyrocatechol or 50mg/L naphthalene was provided.Eligible addition of o-phthalic acid and naphthalene to the reaction system can all stimulate the biodegradation of fluorene by strain W-1. The removal rate of fluorene reached 94.6% and 97.1%, respectively, by the strain W-1, when 50 mg/L of o-phthalic acid or 20 mg/L of naphthalene was provided.