Potential of Candida bombicola URM 3718 Biosurfactant for Application in Removal of Motor Oil Adsorbed on Soils

Soil contamination by petroleum derivatives is a growing environmental issue that affects ecosystems and human health, since the hydrocarbons present in them are persistent and toxic, compromising soil quality and biodiversity. This study investigated the potential of a biosurfactant from Candida bombicola URM 3718, to be applied to remove oils from contaminated soils. After isolation, its main surface-active characteristics were evaluated. The biomolecule was then characterized by NMR and FTIR spectroscopy analyses, and its ability to remove motor oil adsorbed on soils with different particle sizes and its genotoxicity profile were determined. Tests to determine surfactant activities revealed a reduction in water surface tension to 30 mN/m with a critical micelle concentration (CMC) of 0.03 g/L. The surfactant was shown to have a glycolipid nature. The removal of burned engine oil sorbed on various kinds of soil was investigated in both static and kinetic assays using the biosurfactant at different concentrations, namely, ½ CMC (0.015 g/L), CMC (0.03 g/L), and 2 × CMC (0.06 g/L). In the static tests, the maximum removal percentage was 65.32% for burned engine oil adsorbed on sandy soil, 59.04% on silty soil, and 57.42% on clayey soil, while in the kinetic tests, this parameter reached 98.60%, 93.22%, and 92.55% for sandy, silty, and clayey soils, respectively. The genotoxicity profile evaluated in Allium cepa roots did not reveal necrosis or the occurrence of micronuclei in the plant root cap cells, demonstrating that the biomolecule thus produced is not toxic. Such findings, when taken together, indicate that the C. bombicola URM 3718 biosurfactant was effective in removing oils and could, therefore, be used as an alternative agent for remediating hydrocarbon-polluted soil.