The dynamics of diesel oil biodegradation were previously investigated at initial substrate concentrations of 1000 to 20,000 ppm using Gordonia nitida isolated from wastewater. Following the gas chromatogram profiles of diesel oil degradation, diesel oil with concentrations of up to 15,000 ppm was efficiently degraded by this strain. At a concentrations of 20,000 ppm, however, the degradation by this strain was not effective. The enhancement of the biodegradation of diesel oil (at 15,000 and 20,000 ppm) by a synthetic mycolic acid biosurfactant (at 9, 90 and 900 ppm) was also investigated. In G nifida inoculated cultures, the degradation of diesel oil was enhanced by the biosurfactant. For comparison, diesel oil degradation in batch incubations was measured after the addition of rhamnolipid and other surfactants. Synthetic mycolic acid enhanced the degradation to a greater extent than. any other surfactant tested. Additionally, it was demonstrated that the degradation-enhancing property of synthetic mycolic acid was similar to that of rhamnolipid and Tween 80.