Substrate interaction effects during pyrene biodegradation by Pseudomonas aeruginosa RS1

Abstract

Polynuclear aromatic hydrocarbons (PAHs) are typically present in the environment as multicomponent mixtures where system specific substrate interaction effects are inevitable. Substrate interaction effect of different hydrocarbon groups on biodegradation of the high molecular weight PAH (HMW PAH), pyrene by an efficient pyrene degrader, Pseudomonas aeruginosa was investigated in two scenarios. In one scenario, the effect of 2, 3 and 4-ring PAHs, acenaphthene, phenanthrene and fluoranthene on pyrene degradation was determined using the 23 full factorial design where the low and high concentration of each PAH was selected as 25mgL−1 and 100mgL−1, respectively. High concentration of either phenanthrene or fluoranthene or both had statistically significant adverse effect on pyrene degradation while acenaphthene showed minimal adverse effect. Pyrene degradation exceeded 95% when all the PAHs were present at 25mgL−1. In another scenario degradation of pyrene present as a component of a multicomponent non aqueous phase liquid containing low molecular weight (LMW) PAHs and n-alkanes was found to be hindered. Further studies confirmed that the observed recalcitrance was due to nutrient depletion and the adverse effect of LMW PAHs and their metabolites. In the absence of LMW PAHs, pyrene induced P. aeruginosa RS1 could simultaneously degrade pyrene and n-alkanes at a high rate.