Biosurfactants and bioemulsifiers: from contaminated soils to remediation via food-waste valorization

Hydrocarbon-contaminated soils serve as rich ecological niches for the isolation of biosurfactant (BS) and bioemulsifier (BE) - producing microorganisms. This study adopted a waste valorization approach by converting food and agricultural residues into biosurfactants, which can be applied in soil remediation techniques, such as soil washing, soil flushing, and in situ biostimulation. Real contaminated soil was used as inoculum for BS and BE production under anaerobic conditions, with nitrate and sulfate as electron acceptors. A microemulsion composed of waste frying oil and chickpea powder served as the carbon source, while hydrogen peroxide was added to stimulate microbial oxidative activity. The effectiveness of the produced biosurfactants was evaluated using oil displacement and emulsification index (EI24h) tests on various hydrocarbons, including gasoline, diesel, fuel oil, and mineral oil. Biodegradation and stimulation assessments are ongoing, employing either freshly or aged contaminated soils treated with crude or microfiltered biosurfactant mixtures as biostimulants. Phytotoxicity tests on Zea mays, Lepidium sativum, and Sorghum bicolor to assess the safety of these mixtures, are in progress. The overarching goal is to demonstrate that waste-derived biosurfactants can enhance sustainable and cost-effective soil remediation strategies, without the need for microbial bioaugmentation.