Comparison of synthetic surfactants and biosurfactants in enhancing biodegradation of polycyclic aromatic hydrocarbons

TLDR

PAH contamination poses serious health and ecological risks, and while bioremediation offers a low‑cost solution, its effectiveness is limited by slow degradation rates and poor PAH bioavailability; biosurfactants have emerged as a promising alternative that is biodegradable, nontoxic, and avoids micelle formation. Adding surfactants to soil or bioreactors increases PAH solubility and desorption into the aqueous phase, thereby enhancing bioavailability. Synthetic surfactants can inhibit PAH biodegradation through toxicity, stimulation of degraders, or micelle sequestration, whereas biosurfactants show encouraging results but require further study to clarify surfactant–PAH interactions and develop predictive models for improved bioremediation.

Abstract

Abstract Polycyclic aromatic hydrocarbon (PAH) contamination of the environment represents a serious threat to the health of humans and ecosystems. Given the human health effects of PAHs, effective and cost‐competitive remediation technologies are required. Bioremediation has shown promise as a potentially effective and low‐cost treatment option, but concerns about the slow process rate and bioavailability limitations have hampered more widespread use of this technology. An option to enhance the bioavailability of PAHs is to add surfactants directly to soil in situ or ex situ in bioreactors. Surfactants increase the apparent solubility and desorption rate of the PAH to the aqueous phase. However, the results with some synthetic surfactants have shown that surfactant addition can actually inhibit PAH biodegradation via toxic interactions, stimulation of surfactant degraders, or sequestration of PAHs into surfactant micelles. Biosurfactants have been shown to have many of the positive effects of synthetic surfactants but without the drawbacks. They are biodegradable and nontoxic, and many biosurfactants do not produce true micelles, thus facilitating direct transfer of the surfactant‐associated PAH to bacteria. The results with biosurfactants to date are promising, but further research to elucidate surfactant–PAH interactions in aqueous environments is needed to lead to predictive, mechanistic models of biosurfactant‐enhanced PAH bioavailability and thus better bioremediation design.