Sustainable production of microbial protein from carbon dioxide in the integrated bioelectrochemical system using recycled nitrogen sources

Given the urgency of climate change, it is imperative to develop innovative technologies for repurposing CO₂ into value-added products to achieve carbon neutrality. Additionally, repurposing nitrogen-source-derived wastewater streams is crucial, focusing on sustainability rather than conventional nitrogen removal in wastewater treatment plants. In this context, microbial protein (MP) production presents a sustainable and promising approach for transforming recovered low-value resources into high-quality feed and food. We assessed MP production by hydrogen-oxidizing bacteria (HOB) utilizing CO₂ and various nitrogen sources. Specifically, we investigated MP production by two different HOB strains, Cupriavidus necator H16 and Xanthobacter viscosus 7d, within an integrated water-splitting biosynthetic system that generates in situ H₂ via water electrolysis. The electroautotrophically produced MPs of C. necator H16 and X. viscosus 7d exhibited amino acid contents of 555 and 717 mg protein/g cell dry weight, with 243 and 299 mg essential amino acid/g cell dry weight, respectively. They could serve as viable alternatives to conventional food/feed sources like fishmeal or soybean protein. Ammonium-rich wastewater streams are preferable for MP production in integrated bioelectrochemical systems. This study provides valuable insights into sustainable, carbon-neutral MP production using CO₂, water, renewable electricity, and recycled nitrogen sources.