A common biomimetic strategy copies Nature to design the structure and properties of coatings, such as in a lotus leaf design. In an alternative strategy, we directly use Nature (in the form of living bacterial cells) to add functionality to waterborne coatings. Specifically, we have successfully made “biocoatings,” which confine metabolically-active bacteria (e.g. Escherichia coli) within a synthetic colloidal polymer (latex) film. We add nanoclay (halloysite) to build a network of pores to increase the permeability for mass transport, mimicking the structure of natural biofilms. This talk’s focus is on the optimization of the film formation process to achieve biocoatings for the nitrification of wastewater. Biofilm bioreactors are attracting interest in industry, as they allow a higher cell density and thus higher reaction rates compared to conventional bioreactors. Nitrifying bacteria convert ammonium to nitrites and nitrates. However, some commonly used nitrifying bacteria, such as Nitrosomonas europaea, are slow-growing, need a prolonged time to develop a mature biofilm, and are subject to failure. The use of synthetic biocoatings could offer significant time savings and greater robustness. Conventionally, the film formation of biocoatings is achieved by drying a bacteria/latex mixture. However, this process decreases the viability of the encapsulated bacteria because of the osmotic stress induced by desiccation. To address this limitation, we developed a non-desiccating process, which utilizes two colloidal science phenomena: coagulation and wet sintering. The latex binder is coagulated via the deposition of salt on a porous substrate, and then colloidal particles are coalesced in the presence of water. We use a desiccation-sensitive commercial nitrifying bacteria product as a model system to study reactivity. Our results from controlled experiments show that biocoatings fabricated by non-desiccating film formation have a nitrite/nitrate production rate that is five times higher than those fabricated by desiccation. This new technology could be readily applied without additional infrastructure investment to address UN Sustainable Development Goal 6 for access to clean water.

Adding functionality to waterborne coatings with living bacteria for wastewater treatment

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.