Solar Powered Proteins: Providers of Advanced Filtration

By Alex Bernstein

Solar energy is often thought of as a means of powering large machines and structures. Solar panels on homes, schools, and factories are able to capture enough sunlight to provide for the energetic costs of these buildings in an efficient and environmentally sustainable way. Now, scientists are beginning to use solar energy to power systems on the molecular level. Researchers at the University of Cincinnati have developed an organic, solar-powered nano-filter able to remove toxins in water with unmatched efficiency.

The need for high-performance filtration stems out of the presence of unwanted antibiotics and carcinogens in rivers and lakes that arrive there via runoff from farms and chemical plants. Antibiotics in water harm aquatic ecosystems by selecting for the survival of antibiotic resistant bacteria and by reducing populations of other microorganisms. The biodiversity of these ecosystems is thus reduced while the production of antibiotic resistant bacteria rises, posing the threat of higher disease incidence in humans.

The new filter is composed of two bacterial proteins arranged in a sphere. One of the proteins, AcrB, functions as a pump to selectively uptake carcinogens and antibiotics in water to be stored within the sphere. The other, Delta-rhodopsin, captures light energy and transfers it to AcrB to sustain its pumping action. Together, the two proteins are able to filter antibiotics out of water much more efficiently than standard filters. Whereas traditional carbon filters are able to absorb around 40% of the antibiotics in water, the nano-filters are able to absorb up to 64%.

The success of the unit may depend on the bacterial origin of its protein pump. In a normal bacterial cell, AcrB helps eliminate foreign substances, including antibiotics, by pumping them out of the cell. “Our innovation,” comments David Wendell, one of the authors of the report, “was turning the disposal system around. So, instead of pumping out, we pump the compounds into the proteovesicles.”  The ability of AcrB to selectively eliminate antibiotics from bacterial cells is a product of evolution that has allowed for the emergence of highly antibiotic-resistant bacteria. The protein filter, then, stands as an example of a highly beneficial product derived from a nominally harmful source.

Another advantage of the filter is that the antibiotics it collects are able to be recycled. Substances captured in carbon filters cannot be reused because they must be heated hundreds of degrees to be regenerated. The new filters, on the other hand, can be treated after use to retain the collected antibiotics. Moreover, the nano-filter is able to eschew the high energetic costs of carbon filters by relying solely on solar energy.
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The protein filter lies at the intersection of biotechnology and alternative energy. Although the idea of a solar powered filter with the diameter of a human hair sounds absurd, its creation testifies to the highly original and innovative technologies that can be produced from natural products. With nature as its guide, mankind can indeed achieve the improbable.