| Abstract: | This article summarizes the bench‐scale studies to identify pyrene‐degradation pathways using an environmental microbial isolate, Pseudomonas fluorescens 29L. Strain 29L was grown on 50 mg of pyrene per liter of mineral medium. At a pyrene biodegradation rate of 14.7 mg/L of medium/day, 82.38 percent of pyrene was degraded in six days. Naphthalene and phenanthrene accounted for 1.09 percent and 3.69 percent, respectively, of the carbon mass from pyrene in the late log phase. Substituted benzene compounds accounted for 26.10 percent of the carbon mass from pyrene in the late log phase. In the stationary phase, carboxylic acids accounted for 10.44 percent of the carbon mass from pyrene. Strain 29L mutants were used for enzyme assays. Pyrene is oxidized by monoxygenases and dioxygenases, and the oxidized ring is cleaved. These enzymes were induced in the presence of pyrene and their activities peaked in the late log phase. No gentisate 1,2‐dioxygenase activity was detected in Strain 29L wild type (WT), whereas mutant M15 did not show any catechol 2,3‐dioxygenase activity. This indicates the possibility of multiple branchings in the pyrene‐biodegradation pathways. In conclusion, multiple degradative pathways are operating concurrently in this strain. The study shows the versatility of Pseudomonas fluorescens Strain 29L for pyrene degradation. It also emphasizes the need to study pyrene‐degradation pathways in other microorganisms so as to enhance the bioremediation potential for the in situ treatment of pyrene‐contaminated sites. © 2008 Wiley Periodicals, Inc. |
