Developing a biosurfactant to attenuate arsenic contamination in mining tailings

Area of Science:

• Environmental Microbiology
• Bioremediation
• Soil Science

Background:

• Biosurfactants offer a sustainable alternative for soil remediation.
• Arsenic (As) contamination poses significant environmental and health risks.
• Microbial consortia can be engineered for enhanced biosurfactant production.

Purpose of the Study:

• To investigate biosurfactant production by a microbial consortium using different carbon sources.
• To evaluate the efficacy of microbial biosurfactants in mobilizing arsenic from contaminated soil.
• To assess the ecotoxicity reduction of treated soil using Allium cepa.

Main Methods:

• Optimized biosurfactant production by a microbial consortium (Pseudomonas and Stenotrophomonas) under varying conditions (pH, temperature, carbon source ratio).
• Assessed biosurfactant efficiency in arsenic mobilization from soil via sequential soil-flushing.
• Evaluated the ecotoxicity of eluted solutions using the germination index (GI) of Allium cepa.

Main Results:

• Optimal biosurfactant production achieved at pH 9.5, 25 °C, with a 2.5 glucose/glycerol ratio, yielding low surface tension (30 mN.m⁻¹) and high emulsification index (58%).
• Cell-free biosurfactant extracts demonstrated superior arsenic mobilization compared to chemical agents.
• Alkaline treatment with biosurfactants removed 24.6% of arsenic (678 mg/kg) and significantly reduced soil toxicity, increasing the GI from 0 to 55%.

Conclusions:

• Microbial biosurfactants are effective agents for arsenic mobilization and soil remediation.
• The developed biosurfactant-based soil-flushing method is efficient and reduces ecotoxicity.
• Allium cepa serves as a sensitive bioindicator for assessing soil decontamination effectiveness.