Biosurfactant assisted degradation of high ring number PAHs using a two-stage CSTR/fully submerged fixed-film bioreactors in series

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are released into the environment through natural activities such as forest fires and incomplete combustion of wood and decay of vegetable matter. Anthropogenic activities that release PAHs into the environment include activities such as combustion of coal and petroleum product processing. PAHs are not easily accessible to bacteria for degradation due to their low solubility in water. Among the notorious PAH are the high ring number PAHs (ring-number 4 - 7) that are extremely difficult to degrade due to their hydrophobicity which renders them insoluble in water. One such compound, fluoranthene (Flu), is a four ring PAH classified as a High Molecular Weight (HMW) compound. Due to the difficulty to degrade these compounds, it is necessary to find novel and environmentally compatible methods for treating them. In this study, PAH degrading organisms isolated from engine oil contaminated soil achieved 92 % removal of Flu in a fixed-film bioreactor operated at retention time of 1.19 h at 0.86 L.h-1 under fully submerged conditions. The predominant species of biosurfactant producing bacteria in the reactor were determined to be dominated by Pseudomonas aeruginosa using 16S rRNA genotype fingerprinting analysis.