Engineering Molecular Efflux Pumps for Bioremediation of Groundwater

The present technology standard for removal of emerging contaminants in groundwater is activated carbon, which is commonly used in water treatment for removing a variety of organic contaminants such as synthetic organic chemicals (SOCs), aromatic compounds and natural organic matter (NOM). While activated carbon can remove a broad range of organic substrates, the cost of this prolific absorbance is specificity. Despite the advantage of high COD removal efficiencies, contaminants such as antibiotics escape capture due to their relatively low abundance compared to other organic matter. Also, heat regeneration of activated carbon is critical for efficient removal and increased useful lifetime of the media, but remains energy intensive. Clearly, there is a need for an effective and selective antibiotic removal material, capable of functioning in organics-rich wastewaters with minimum energy input. Here we demonstrate the selective removal of ampicillin and vancomycin, commonly used human and veterinary antibiotics, and ethidium bromide, a common molecular biology reagent, by engineering a light powered proteovesicle molecular assembly using the multidrug efflux pump protein AcrB. We have provided the requisite pmf by coupling this pump to the light-driven proton pump delta-rhodopsin (dR). This creates a solar powered material capable of pumping and capturing antibiotics from bulk solutions. When comparing the removal effeciency of our system to an equivalent amount of activated carbon using river water and sunlight, our vesicle system removed approximately twice as much antibiotic. In addition to capture, our system also offers the ability to recover antibiotics for reuse.  Altogether, the AcrB-dR technology enables an environmental friendly and cost-effective means for extracting antibiotics from surface waters, while also allowing potential antibiotic recovery and reuse through vesicle solubilization.