Screening and Environmental Safety Assessment of Biosurfactant-Producing Bacteria from Tunisian Soil

Biosurfactant-producing bacteria represent a promising and environmentally compatible alternative to synthetic surfactants; however, their large-scale application requires careful assessment of potential ecological toxicity and environmental impact. In this study, several bacterial strains were isolated from Tunisian soil and systematically screened for their ability to produce biosurfactants using standard qualitative and quantitative assays. The most efficient producers were selected for further characterization, and the biosurfactants obtained were evaluated for their environmental safety through a series of toxicity, stability, and biodegradability tests.

Phytotoxicity assays using Lepidium sativum seeds at biosurfactant concentrations ranging from 10 to 1000 mg/L showed no inhibitory effects on seed germination or root elongation, with a germination index (GI) exceeding 80% at all tested concentrations, indicating the absence of phytotoxicity. Biodegradability studies demonstrated rapid degradation, with more than 60% degradation achieved within four days, highlighting the biosurfactant's low environmental persistence. Stability assays showed that the emulsification activity (E24) remained stable after exposure to temperatures between 30 and 80°C and within a pH range of 4–10, demonstrating the robustness of the biosurfactant under a wide range of environmental conditions.

Overall, the results confirm that biosurfactants produced by the isolated soil bacteria exhibit a favorable ecotoxicological profile, supporting their potential use as safe, sustainable, and efficient agents in bioremediation and other environmental biotechnological applications.