Enhancement And Downstream Pathway Of Pyrene Degradation By Ochrobactrum Sp. PW

Polycyclic aromatic hydrocarbons (PAHs) are a class of organic pollutants exists widely in soil, water and other natural environment mainly as a result of incomplete combustion of coal, oil and other carbon containing compounds. PAHs pose a significantly risk to environment and a potential theat to human health because of the characteristicals of the "Teratogenicity, carcinogenicity and mutagenicity" effect, the difficulty to degraded due to stable chemcial structure and the highly fat soluble for accumulating in human body through food chain. Therefor, the remediation of PAHs pollution is crucial to reduce the risk.The pyrene and the Ochrobactrum sp. PW which was isolated from pyrene contaminated soil by laboratory were used as study object in this paper. The effect of cometabolism on pyrene degradation by Ochrobactrum PW, the effect of (NH4)2SO4, K2HPO4 and FeSO4 concentration on pyrene, the application of surface active agent and the two-phase partitioning bioreactor (TPPB) for bioremediation of PAHs and pyrene degradation downstream metabolic pathway by Ochrobactrum sp. PW were studied in this paper. The main results are as follow:(1) Yeast extract was the best one of the four kinds of crabon sourse selected for promoting pyrene degradation by Ochrobactrum sp. PW. Yeast extract could promote the degradation of pyrene When its concentration was 50 mg/L, but inhibit the degradation of pyrene when its concentration was more than 100 mg/L. It could promote the degradation of pyrene when the concentration of FeSO4 in mineral salt medium (MSM) increased from 1 mg/L to 2 mg/L, and it would inhibited degradation of pyrene when concentrations of (NH4)2SO4 and K2HPO4 in MSM were changed.(2) Tween80 could significantly increase the solubility of pyrene in water, and the solubility of pyrene increased with the increasing of Tween80 concentration. Tween80 could promote the pyrene degradation through improving the utilization efficiency of pyrene by Ochrobactrum sp. PW, for example, when the pyrene concentration was 100 mg/L, the pyrene degradation were 80.3%-91.1% and 88.6%-93.5% respectively as the tween80 concentration were 100 mg/L and 250 mg/L, and these were both higher than that of the control group, which was 73.3%-92.5%. But it would inhibit the pyrene degradation when the Tween80 concentration was too high, and the higher the concentration of Tween80, the lower degradation rate of pyrene.(3) the TPPB had a certain role in promoting the pyrene degradation by Ochrobacterum sp. PW. Effect of TPPB on the pyrene degradation was affected by the category and ratio of organic phase, the concentration of pyrene, liquid velocity of disturbance and other factors. A larger pyrene degradation rate was showed resulted from increasing of the interfacial area and the mass transfer rate with increasing of agitation rate. for the same class of organic phase, appropriately increasing of organic phase ratio had a active effect on pyrene degradation when the pyrene concentration was higher. For example, when the concentration of pyrene was 1000 mg/L, and the organic phase ratio was 2.5%-20%, the pyrene degradation rate was 24.3%-44.3% in water-hexadecane system, and 22.6%-48.8% in water-octadecane system, respectively. On the contrary, the proportion of organic phase should been reduced when the pyrene concentration was lower.(4) There were two downstream pathways of pyrene degrading by Ochrobactrum sp. PW, one was phthalate pathway, and the other one was salicylic acid pathway. In salicylic acid pathway, the salicylic acid was not degradated to catechol, but through other ways to enter the TCA cycle.