Hydrocarbon degradation by a soil microbial population with beta-cyclodextrin as surfactant to enhance bioavailability

In general the biodegradation of nonchlorinated aliphatic and aromatic hydr ocarbons is influenced by their bioavailability. Hydrocarbons are very poor ly soluble in water. They are easily adsorbed to clay or humus fractions in the soil, and pass very slowly to the aqueous phase, where they are metabo lised by microorganisms. Surfactants that increase their solubility and imp rove their bioavailability can thereby accelerate degradation. Cyclodextrin s are natural compounds that form soluble complexes with hydrophobic molecu les. They are widely used in medicine and harmless to microorganisms and en zymes. This paper describes their in vitro effect on the biodegradative act ivity of a microbial population isolated from a petroleum-polluted soil, as shown by the decrease of dodecane (C12), tetracosane (C24) anthracene and naphthalene added individually as the sole carbon source to mineral medium liquid cultures. beta -cyclodextrin accelerated the degradation of all four hydrocarbons, particularly naphthalene, and influenced the growth kinetics as shown by a higher biomass yield and better utilization of hydrocarbon a s a carbon and energy source. Its low cost, biocompatibility and effective acceleration of degradation make beta -cyclodextrin an attractive option fo r bioremediation. (C) 2000 Elsevier Science Inc. All rights reserved.