Recycling of minerals with acetate separation in biological syngas fermentation with an electrodialysis system

Abstract

The current study proposes integrating syngas fermentation and electrodialysis (ED) systems to reduce operating costs of fermentation process by reusing nutrients required for biocatalyst growth as well as separating the ionized product, acetate. By reusing nutrients, the nutrient and mineral limitations that generally occur in high cell density conditions are resolved. Eubacterium callanderi KIST612, used as a biocatalyst, improved acetate titer by 25 % (264 mmol/L) in the ED-integrated process by avoiding nutrient and mineral limitations. A high extraction rate (>99.8 %) of acetate was also achieved, and divalent cations were maintained in the residual medium using mono-selective cation exchange membranes (CEMs) in the ED system. Cell growth was assessed using a residual medium, showing that this integrated system could be operated without any additional treat-ment of residual medium. A case study for cost and carbon footprint analyses demonstrated that reusing the residual medium can reduce medium cost (16.5 %-29.6 %) for syngas fermentation as well as reduce the carbon footprint. These results suggest that reusing the medium while extracting acetate in ED could potentially resolve issues of operational expenditure and carbon emissions in the industrial syngas fermentation process.