PAH degrading capability of microbes isolated from hydrocarbon contaminated sites

Abstract

The polyaromatic hydrocarbons (PAH) are occurred in petroleum, petroleum derivatives, or its products and come off from the incomplete combustion of organic matters. These compounds are hardly degradable (persistent) in the environment. Human health risk of PAHs caused by their mutagenic, teratogenic and endocrine distrupting effects. Seven PAH compounds were identified as human carcinogenic by WHO, IARC and US EPA. The aim of our work was to look for microorganisms, which can be applied for biodegradation of PAHs. Bacteria were selected from the microbial culture collections of SZIU, Department of Environmental Protection and Environmental Safety. These microbes were previously isolated from soil and groundwater samples of Hungarian hydrocarbon (TPH, BTEX, PAHs) contaminated sites. The PAH degrading ability of chosen microorganisms were tested in three steps. In the first step, the method of Chinese researchers (Zhao et al., 2009) was used for screening the collection with three compounds [benzo(a)pyrene, benzo(a)anthracene, fluoranthene] to select possible degrading strains. In the second step PAH containing shaking cultures were used to verify degrading ability of the selected strains in vitro. Strains were paired for increasing degradation rate because, by the results of scientific references, a mixture of strains generally have improved degrading ability. Prior strain pairing tests were performed to analyze the multiplications of selected microbes together in mixed cultures. The third step was a degradation and soil respiration test (OxiTop, WVR International Inc.) with PAH and TPH polluted soil sample from a Hungarian contaminated site. The intensification of respiration and PAH degrading were compared between the control, and inoculed (with strain pairs) ones. Our results could lead to the creation of a PAH degrading inoculum, which can be used in contaminated sites, in vivo.