Self-sustained ammonium recovery from wastewater and upcycling for hydrogen-oxidizing bacteria-based power-to-protein conversion

Microbial protein (MP) production by autotrophic hydrogen-oxidizing bacteria is regarded as a potentially sustainable approach to mitigate food crisis, water pollution, and climate change. Herein, a hybrid biological-inorganic (HBI) system which coupled energy-neutral ammonium recovery and in-situ upcycling for MP production was demonstrated. No energy and acids/bases were needed for ammonium recovery and pH control. The system was tested with different amounts of CO₂ supply and operated at different operational modes (microbial fuel cell or microbial electrolysis cell mode). 0.381 g/L of biomass containing 64.79% of crude protein was produced using the recovered nitrogen and therefore led to 76.8% of ammonium recovery and 84.6% of COD removal from real municipal wastewater. The system although not yet optimal in terms of efficiency has a meaning in alleviating food crisis and environmental issues. Altogether, this study offers insight into developing an energy and resource-efficient power-to-protein process to supplement conventional food production globally.