Degradation of polyaromatic hydrocarbons by Burkholderia cepacia 2A-12

Abstract

A new strain of bacterium degrading polyaromatic hydrocarbons (PAHs), Burkholderia cepacia 2A-12, was isolated from oil-contaminated soil. Of three PAHs, the isolated strain could utilize naphthalene (Nap) and phenanthrene (Phe) as a sole carbon source but not pyrene (Pyr). However, the strain could degrade Pyr when a cosubstrate such as yeast extract (YE) was supplemented. The PAH degradation rate of the strain was enhanced by the addition of other organic materials such as YE, peptone, glucose, and sucrose. YE was a particularly effective additive in stimulating cell growth as well as PAH degradation. When 1 g YE l(-1), an optimum concentration, was supplemented into the basal salt medium (BSM) with 215 mg Phe l(-1), the specific growth rate (0.30 h(-1)) and Phe-degrading rate (29.6 mumol l(-1) h(-1)) were enhanced approximately ten and three times more than those obtained in the BSM with 215 mg Phe l(-1), respectively. Both cell growth and PAH degradation rates were increased with increasing Phe and Pyr concentrations, and B. cepacia 2A-12 had a tolerance against Phe and Pyr toxicity at the high concentration of 730-760 mg l(-1). Through kinetic analysis, the maximum specific growth rate (mu(max)) and PAH degrading rate (v(max)) for Phe were obtained as 0.39 h(-1) and 300 mumol l(-1) h(-1), respectively. Also, mu(max) and v(max) for Pyr were 0.27 h(-1) and 52 mumol l(-1) h(-1), respectively. B. cepacia 2A-12 could simultaneously degrade crude oil as well as PAHs, indicating that this bacterium is very useful for the removal of oils and PAHs contaminants.