Biosurfactants from Acinetobacter calcoaceticus BU03 Enhance the Bioavailability and Biodegradation of Polycyclic Aromatic Hydrocarbons

Biosurfactants produced by an isolated thermophilic strain Acinetobacter calcoaceticus BU03 were demonstrated to be effective in enhancing the solubility of polycyclic aromatic hydrocarbons (PAHs) and the present study aimed at investigating its effectiveness in increasing bioavailability of PAHs in soil for biodegradation under thermophilic composting condition. At 25 times of its critical micelle concentration (CMC), biosurfactants by BU03 significantly increased the apparent aqueous solubility of phenanthrene (PHE) and benzo[a]pyrene (B[a]P) to 54.3 and 2.08 mg L, respectively. After confirmation of its ability in enhancing the solubility of PAHs, the isolated biosurfactants were applied to a thermophilic soil composting system. Within 42 days of composting period, the degradation of PHE and B[a]P in the absence of the biosurfactants was 71.2 and 16.4%, respectively. Inoculation of A. calcoaceticus BU03 or biosurfactants produced by this strain significantly increased the emulsifying capacity of soil, and therefore enhanced the desorption of PAHs from soil to aqueous phase in which they can be degraded by an inoculated degradative strain Bacillus subtilis B-UM. Therefore inoculation of A. calcoaceticus BU03 or biosurfactants from BU03 together with inoculation of B. subtilis B-UM increased the degradation of B[a]P to 83.8 and 65.1%, respectively, while PHE was almost completely removed with these two treatments. The results indicate that the application of biosurfactants produced by A. calcoaceticus is an effective means to enhance the biodegradation of PAHs in thermophilic composting, while inoculation of biosurfactants producing strains in PAHs contaminated soil is a more practical and cost-effective approach than direct addition of biosurfactants. Corresponding author: Jonathan W.C. Wong: Sino-Forest Applied Research Centre for Pearl River Delta Environment, Department of Biology, Hong Kong Baptist University, Hong Kong SAR, P.R. China, Tel: +852 34117056, Fax: +852 34112355, Email: [email protected]. Wong et al.: Biosurfactants from Acinetobacter calcoaceticus BU03 Enhance the Produced by The Berkeley Electronic Press, 2010 Biosurfactants from Acinetobacter calcoaceticus BU03 37