Abstract
Polycyclic aromatic hydrocarbons (PAHs) present in the petroleum wastewater are ubiquitous environmental pollutants. They are generated from both natural and anthropogenic processes, and pose a serious concern on the health of aquatic life and human beings through bioaccumulation. PAHs are known to be cytotoxic, mutagenic and carcinogenic. They persist in the environment due to their hydrophobic nature and are difficult to treat using chemical methods. This chapter details the biodegradation of PAHs under extremophilic condition. Bacteria, fungi and algae are reported to be used in the treatment of PAHs. Extremophilic conditions such as acidophilic (pH 1-5), alkaliphilic (pH > 9) halophilic (> 3 % salt), thermophilic (temperature > 50 degrees C), psycrophilic (temperature < 10 degrees C), piezophilic or barophilic (pressure > 38 MPa) and xerophilic (a(w) 0.60-a(w) 0.90) conditions. Collection of samples, isolation of extremophilic micro-organism, mineralization of hydrocarbons and identification of microbes using molecular techniques are detailed. Despite the microbial ability to degrade petroleum hydrocarbons, there are factors such as temperature, pH and nutrients that influence the degradation of hydrocarbons. Information on mechanisms and pathways for petroleum hydrocarbon degradation under extreme conditions is scarcely known and recently few studies reported on enzymes, genes and metabolism of hydrocarbons. Microbial cell interaction with petroleum hydrocarbons are also detailed in this chapter. Extremophiles play a vital role in the degradation of petroleum hydrocarbons and in the treatment of refinery wastewater.