Nickel-Coated ceramic hollow fiber cathode for fast enrichment of chemolithoautotrophs and efficient reduction of CO2 in microbial electrosynthesis

Microbial electrosynthesis (MES) explores the potential of chemolithoautotrophs for the production of value-added products from CO2. However, the enrichment of chemolithoautotrophs on a cathode is relatively slow and the separation of the products is energy intensive. In this study, a novel and multifunctional cathode configuration, enabling the simultaneous enrichment of chemolithoautotrophs and separation of acetate from MES, was developed through one-step electroless nickel plating on ceramic hollow fiber (CHF) membrane. A thick layer of chemolithoautotrophs with 5.2 times higher cell density, which was dominated by Sporomusa (68 % of the total sequence reads in biocathode), was enriched on the membrane cathode surface through suspended biomass microfiltration compared to MES reactors operated without filtration. Simultaneously, >87 % of acetate (31 mM) per batch could be harvested after catholyte microfiltration. The Ni content was > 80 % on the CHF surface after long-term operation in the two-chamber MES system, which exhibited 78 % lower charge transfer resistance compared to three-chamber MES system (∼110 vs 510 Ω) for acetate separation/extraction. The ease of product separation in two-chamber MES systems and the fast establishment of chemolithoautotrophs on the cathode are a step forward in realizing MES systems as a promising platform for CO2 reduction and biochemical production in a circular carbon bioeconomy.