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Screening and Kinetics of High Strength Phenol Degrading Bacterial Strains

Author: WangQian
Tutor: LiuJianZhong
School: Wuhan University of Science and Technology
Course: Chemical processes
Keywords: phenol biodegradation Pseudomonas sp. catabolic pathway catechol-1, 2-dioxygenase kinetics
CLC: X172
Type: Master's thesis
Year: 2011
Downloads: 150
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Abstract

The phenol, belongs to aromatic compound with high toxic and recalcitrant to degradation, is the raw or middle materials during the fields of paper-making, tar and oil factory. Recently wastewater with high concentration phenol posed serious threats on the environment. The phenol removal by biodegradation, especially the bioaugmentation with effective microbes, is one of economic and effective ways. Bacteria that can effectively degrade phenolic compound had been isolated from natural environment, they can be poured into waste water treat system and obviously enhance the effect, therefore, they have extraordinary potential in bioremediation.50 bacterial strains capable of biodegrading phenol were isolated from activated sludge of the wastewater of coke oven industry in Wuhan, P. R. China. One strain Wust-C1 was selected for detailed studies because of its capable of tolerating high phenol concentrations with high degrading ef?ciency and relatively rapid growth in MSM. The strain was identified as Pseudomonas sp. according to morphological,physiological and biochemical characteristics and 16S rRNA sequence analysis. The 16S rRNA sequence of strain WUST-C1 was submitted to GenBank（GenBank code JN180124）.The growth and phenol degradation capability of strain WUST-C1 were investigated. The optimum conditions for the degradation of phenol were: 35℃, pH 7.0, 150 r/min and 5 % of inoculation amount, respectively. Under the optimal conditions, WUST-C1 could degrade over 99 % of phenol （1200 mg/L） within 36 h. It could tolerate 1600 mg/L of phenol utilized as the sole carbon source. WUST-C1 is also able to degrade other aromatic compounds, such as hydroquinone, naphthalene, catechol, isoquinoline, 1-naphthol, indol, etc. and is resistant to ampicillin and chloroamphenicol.The effects of environmental factors on the growth and phenol degradation were investigated. The results indicated that additional carbon source cannot accelerate the growth of WUST-C1 and phenol degrading, glucose would inhibited significantly the degradation of phenol. Phenol could completely by WUST-C1 within 18h with NaNO₃ or KNO₃ as nitrogen source, but 36h with （NH₄）₂SO₄ or NH4NO3. Cu²⁺, Cd²⁺, Co²⁺, Cr6+ inhibited the growth of WUST-C1 and phenol degradation due to their high toxicity. Mn²⁺ could accelerate the phenol degradation. The efficiency of phenol degradation of the strain descends gradually with the increase of NaCl concentration. WUST-C1 lost their growth activity when the concentration of NaCl is 1.5 %.In this thesis, the phenol catabolic pathway of strain WUST-C1 was evaluated by PCR amplification of the key enzyme encoded gene and activity. It was demonstrated that the degradation of phenol was catalyzed by catechol-1,2-dioxygenase. Kinitcs study was performed using phenol as the sole carbon and energy,the initial phenolconcentration was varied from 0 to 1600 mg/L. Haldane type substrate inhibit model was used to simulate the cell growth on phenol, as for the substrate degradation. The result showed that the models can well describe the experimental results.

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