Injectable cationic traps and sticky bacterial emulsifiers: A safe alliance during diesel bioremediation

This study proposes injectable polymeric filters to prevent diesel migration during its bioremediation. Pseudomonas aeruginosa (Gram negative bacterium) was isolated from forest soil and used to biodegrade diesel. P. aeruginosa produced biosurfactants that emulsified diesel in water while degrading it, by decreasing the interfacial tension and forming skins around diesel droplets. In lab experiments, emulsified diesel droplets could migrate through model soil columns (sand and limestone) saturated with water (to mimic aquifers). These results indicate that clean aquifers downstream of diesel spills are at risk of becoming contaminated during diesel bioremediation by P. aeruginosa. Injectable filters were developed to mitigate this risk. Injectable filters were obtained by injecting into model soils aqueous solutions of quaternized hydroxyethylcellulose (HEC+, with a positive electrostatic charge). HEC + adsorbed onto model soils, yielding positively charged surfaces. Diesel droplets stabilized by P. aeruginosa had a negative electrostatic charge (as demonstrated through zeta potential measurements) and adhered onto HEC + coated soil, likely due to attractive electrostatic forces. As a result, diesel droplet mobility through soil columns decreased. Our proof of concept indicates that injectable HEC + filters can protect clean regions of aquifers during the bioremediation of diesel spills by P. aeruginosa.