Pyrene Degradation by Pseudomonas fluorescens Strain 29L

摘要

The intermediates and the enzymes involved in pyrene degradation by Pseudomonas fluorescens Strain 29L were studied. Strain 29L was grown with pyrene (50 mg/L) as the sole carbon and energy source. The GC-MS analysis showed the presence of two- and three-fused-ring PAHs which accounted for 21.8% of the carbon from pyrene in the mid-log phase. These decreased to 9.48% into the late log phase with an increase in the hydroxyl and carboxylic acid substituted benzenes accounting for 15.1% of the carbon from pyrene. By day 6, in the stationary phase when 91.1% of the pyrene had been degraded, citric, oxalic, and pyruvic acids were present in higher concentrations compared to the other intermediates. These three acids accounted for 10.4% of the carbon from pyrene on day 6. Results from the enzyme assays showed that the wild type Strain 29L and mutant 38 did not have any gentisate 1,2 dioxygenase activity, while mutant 15 did not show any catechol 1,2 dioxygenase activity. All the enzymes were induced by pyrene and peaked in the log phase. The exception was salicylate 5-hydroxylase, which had increased activity in the stationary phase. These data indicate that Pseudomonas fluorescens Strain 29L degrades pyrene by multiple pathways.