Living Reverse Osmosis Membranes: A Model for the Beneficial Use of Engineered Biofilms

Reverse osmosis membrane systems, increasingly used for developing new water sources and recycling water, are a key technology to ensure water sustainability. However, as with all membrane water treatment processes, biofouling, the build-up of microbes and their polymeric matrix, clogs these systems and reduces their efficiency. Realizing that a microbial film is inevitable, we engineered a beneficial biofilm that prevents membrane biofouling by limiting its own thickness by sensing the number of its cells that are present via a quorum-sensing circuit; the beneficial biofilm also prevents biofilm formation by deleterious bacteria by secreting nitric oxide, a general biofilm dispersal agent. In addition, the beneficial biofilm was engineered to produce an epoxide hydrolase so that it efficiently removes the environmental pollutant epichlorohydrin. Thus, we have created a living reverse osmosis system that simultaneously reduces biofouling while providing a platform for biodegradation of persistent organic pollutants.