Microbial Electrosynthesis Using 3D Bioprinting of Sporomusa ovata on Copper, Stainless-Steel, and Titanium Cathodes for CO2 Reduction

Abstract

Acetate can be produced from carbon dioxide (CO2) and electricity using bacteria at the cathode of microbial electrosynthesis (MES). This process relies on electrolytically-produced hydrogen (H2). However, the low solubility of H2 can limit the process. Using metal cathodes to generate H2 at a high rate can improve MES. Immobilizing bacteria on the metal cathode can further proliferate the H2 availability to the bacteria. In this study, we investigated the performances of 3D bioprinting of Sporomusa ovata on three metal meshes—copper (Cu), stainless steel (SS), and titanium (Ti), when used individually as a cathode in MES. Bacterial cells were immobilized on the metal using a 3D bioprinter with alginate hydrogel ink. The bioprinted Ti mesh exhibited higher acetate production (53 ± 19 g/m2/d) at −0.8 V vs. Ag/AgCl as compared to other metal cathodes. More than 9 g/L of acetate was achieved with bioprinted Ti, and the least amount was obtained with bioprinted Cu. Although all three metals are known for catalyzing H2 evolution, the lower biocompatibility and chemical stability of Cu hampered its performance. Stable and biocompatible Ti supported the bioprinted S. ovata effectively. Bioprinting of synthetic biofilm on H2-evolving metal cathodes can provide high-performing and robust biocathodes for further application of MES.

Isolation and characterization ofSporomusa carbonissp. nov., a carboxydotrophic hydrogenogen in the genus ofSporomusaisolated from a charcoal burning pile

“…Recently, S. ovata was shown to employ a three subunit Sporomusa-type Nfn transhydrogenase (Stn) instead of the two subunit Nfn transhydrogenase used by other acetogens for linking the redox pool of NADH and reduced ferredoxin during autotrophy to the cellular redox pool (NADPH) [16]. Biotechnological applications of bacteria from the genus Sporomusa have focused on the CO2-based production of bulk chemicals and biofuels via microbial electrosynthesis [17][18][19][20][21][22] or via a bacterial CdS biohybrid system [23]. S. ovata is particularly suitable for microbial electrosynthesis, as it exhibited some of the lowest H2threshold found in described for acetogens [24].…”