(384h) Polyethylene Glycol-Based Hydrogel Coatings for Protection of Electroactive Bacteria Against Chemical Shocks

Microbial electrochemical cells (MxCs) are an environmental biotechnology platform used for producing renewable energy, carbon and nutrient recovery, and synthesis of chemicals. Essential to the operation of MxCs are anode-respiring bacteria (ARB) that consume simple organic substrates like acetate to produce electrical current. However, to be used in wastewater treatment, ARB must be able to resist toxins such as ammonia-N, bleach, and oxidants like hydrogen peroxide. Here, polyethylene glycol (PEG) based hydrogels are investigated for use as an interface on bioanodes for protection against chemical shocks, specifically for the protection of ARB from toxic concentrations of ammonia spikes. PEG hydrogels were formed using thiol-vinyl sulfone crosslinking chemistry and were first demonstrated to have long-term stability over the bioanode for more than 30 days. The transport of ammonia and acetate through the PEG coatings were simulated using steady and unsteady states COMSOL models. The response of coated electrodes to ammonia toxicity was then evaluated at different concentrations to explore the potential of the coating for protection of ARB biofilms. Prior to the ammonia shock, the uncoated electrode reached a higher current density of 4-6 A/m² compared to 3-5 A/m² for the coated electrode. During the ammonia spike, the coated electrode had a lower reduction of current density which resulted in a higher current density compared to the uncoated electrode. This positive impact lasted for about 8 hours before the toxicity of the ammonia-N outweighed the impacts of the protective coating. These studies present a foundation for further development of protective hydrogel coatings to improve MxC operation in unfavorable chemical environments.