Desorption and solubilization of anthracene by a rhamnolipid biosurfactant from Rhodococcus fascians

The rhamnolipid biosurfactant‐producing bacterium, strain SDRB‐G7, was isolated from the sediment of Sindu‐ri beach and identified as Rhodococcus fascians based on a phylogenetic analysis. Optimal activity, with the highest yield (2.441 g/L) and surface tension‐reducing activity (24.38 mN/m), was observed when the cells were grown on olive oil as their sole source of carbon at pH 8.0. The rhamnolipid biosurfactant showed environmental stability at a variety of NaCl concentrations (2‐20%) and pH values (2‐12) even under acidic conditions. Of the initial anthracene, 66% was solubilized by 100% crude biosurfactant. Furthermore, 100% crude biosurfactant desorbed 81% of the anthracene in sediment into the aqueous phase. These results suggest that the rhamnolipid biosurfactant produced from R. fascians SDRB‐G7 is a promising candidate for polycyclic aromatic hydrocarbon (PAH) removal from the sediment and can be an effective agent for processes that bioremediate PAHs such as surfactant‐enhanced remediation. Practitioner points Biosurfactants can accelerate desorption of PAHs and improve their solubility. BS‐producing R. fascians SDRB‐G7 was selected by screening of biochemical tests. Solubility of anthracene was enhanced by rhamnolipid produced by strain SDRB‐G7. Microbial surfactant is a promising alternative for bioremediation of PAH‐polluted sites. Rhodococcus facians SDRB‐G7 produced rhamnolipid biosurfactants with environmental stability at various NaCl concentration (2–20%) and pH (2–12).