Biosurfactant-assisted biodegradation of fluoranthene in a two-stage continuous stirred tank bio-reactor system using microorganism

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are known to be resistant to environmental degradation due to their hydrophobicity which results in low solubility in water. PAHs are therefore typically less bioavailable than other non-aromatic compounds in the same range of molecular weight. One of the PAHs, fluoranthene, is a four-ring PAH rated among the top 16 PAHs which are included in the list of priority pollutants by the U.S.EPA. Like other PAHs, fluoranthene is a mutagenic, carcinogenic and toxic compound with known potential risks to human health and the environment. In this study, cultures of biosurfactant producing bacteria were isolated from engine oil contaminated soil at a car servicing facility in Pretoria (South Africa). Biodegradation of fluoranthene was conducted using the isolated culture in two Continuous Stirred Tank Reactors (CSTRs) in series followed by polishing treatment in a packed-bed biofilm reactor. Optimum operation times for the CSTR and biofilm system was based on the optimum incubation time and experimental results from batch systems. Results showed that up 93 % fluoranthene was degraded during runs that utilised the enriched inoculum from engine oil contaminated soil. The open system was easily optimised based on target feed rate, hydraulic retention time (HRT) and biomass yield. Analysis of the 16S rRNA gene of the biosurfactant producing inoculum showed that the strains isolated were 100 % homologs of Pseudomonas aeruginosa.