The project set out to evaluate and develop microbial electrosyntheses (MES) for producing biofuels and bulk chemicals from carbon dioxide, using electrons supplied by a cathode to microorganisms. The aim was to create a highly efficient, renewable‐energy‐driven bioprocess that could replace conventional plant‑based feedstocks. To achieve this, the research team at the DECHEMA Research Institute combined expertise from microbiology, molecular biology, electrochemistry and engineering in an interdisciplinary framework.

Technically, the work was organized into four main work packages. In the first package, new methanogenic strains capable of CO₂ fixation were identified and characterized, expanding the pool of organisms suitable for MES. A screening platform based on quartz crystal microbalance (qCM) sensors was developed to monitor biofilm formation on electrodes, and a complementary confocal laser scanning microscopy method was introduced for detailed biofilm analysis. The team compared direct electron transfer and mediator‑assisted transfer, ultimately selecting the most efficient strategy for each organism. Production rates were optimized by tuning electrode potentials, biofilm thickness, and medium composition, leading to measurable increases in product yields, although specific numerical values were not disclosed in the report.

The second package focused on electrochemical reaction systems. The researchers demonstrated that electrochemical cues could steer biofilm development and immobilize microorganisms on three‑dimensional electrode architectures, improving electron accessibility. They also investigated potential coupling reactions at the anode, identifying conditions that could generate additional value streams without compromising the MES process.

In the third package, the electron transfer machinery from Shewanella oneidensis (MtrA, MtrB, MtrC) was expressed in the heterologous host Ralstonia eutropha. While functional expression was confirmed, a clear performance advantage over the native system was not yet achieved. Evolutionary engineering was applied to select mutants with enhanced electron transfer rates and product formation, and several promising isolates were identified. Parallel work on Shewanella mutants led to the production of bulk chemicals, and the growth of Clostridium neator on hydrogen as an electrochemical mediator was optimized, broadening the range of usable substrates.

All major milestones were reached within the planned schedule, with only a few minor delays. The project produced a series of peer‑reviewed publications and a commercialization strategy outlining potential industrial applications. The collaborative effort involved DECHEMA scientists, external partners from academia and industry, and was funded by German research agencies, reflecting the national priority to develop next‑generation biotechnological processes. Over the course of the project, the team established a robust MES platform, demonstrated the feasibility of integrating electrochemical and biological components, and laid the groundwork for scaling up renewable CO₂ conversion into valuable chemicals.