eBioCO2n – Electricity-driven CO2 conversion through synthetic enzyme cascades

Many industries are setting their sights on CO2 as an important raw material for syntheses in the context of developing climate friendly, resource-efficient innovations, and the chemical industry is no exception. That means CO2 will play an important role in the future right alongside renewable raw materials, as the greenhouse gas can be converted into other substances using renewable electricity.

To help achieve this transition, a multidisciplinary research team from the Bioinspired Chemistry innovation field at Fraunhofer IGB is developing a new, modular electro-biocatalytic process in the Fraunhofer project eBioCO2n, funded under the collaboration program with the Max Planck Society. Using electricity and under very mild reaction conditions, the process fixes CO2 to a substrate, so that it can then be used to manufacture valuable fine chemicals by means of carefully coordinated enzyme cascades.

A new electro-biocatalytic CO2 reduction process for synthesizing fine chemicals


Not only chemical-catalytic processes can be considered for the current-driven synthesis of chemicals. It is also conceivable to combine CO2-fixing electron-transmitting biocatalysts with further enzymatic conversion steps in the form of an enzyme cascade for the production of fine chemicals.

Solution approach

The "eBioCO2n" project, which is being carried out jointly by Fraunhofer and Max Planck researchers, meets this challenge. The aim of this ambitious project is to demonstrate the feasibility of such bioelectrocatalytic syntheses with a demonstrator on a 10 – 100 mL scale. To this end, suitable C02-fixing enzymes are to be assembled on electrodes (cathodes) using new molecular architectures and – depending on the target product – combined with other specific enzymes to form continuous and coupled reaction cascades. Recently discovered redox enzymes, enoyl-CoA carboxylases/reductases (ECRs), are used as CO2-fixing biocatalysts. They are among the most efficient CO2-converting biocatalysts described so far.

Using hydrogel to transport electrons to the CO2 fixation enzymes

Special redox enzymes called enoyl-CoA-carboxylases/reductases, developed by Prof. Tobias Erb’s research group at the Max Planck Institute for Terrestrial Microbiology in Marburg, are being used for the biocatalytic CO2-fixation. These bind CO2 to a substrate by means of reductive carboxylation, transforming it into a valuable intermediate in the process. The enzymes are among the most efficient biocatalysts ever recorded when it comes to CO2 conversions.

The CO2 fixation enzymes are immobilized on electrodes in a custom-made redox-active hydrogel consisting of polymers grafted with viologens. This ensures an efficient, continuous transfer of the electrons supplied by renewable electricity. The basic principles allowing the three-dimensional flow of electrons were developed by a team from the Technical University of Munich (TUM), led by Prof. Nicolas Plumeré. This three-dimensional flow makes it possible to use larger quantities of enzymes, meaning that a higher product yield can be achieved.

Infographic eBioCO₂n
© Fraunhofer IGB
eBioCO₂n platform for the electrically driven fixation of CO₂ into crotonyl-CoA to form (2𝘚)-ethylmalonyl-CoA.

Regenerating the cofactor

For the reductive carboxylation reaction to take place, the enzyme enoyl-CoA-carboxylase/reductase requires NADPH as a cofactor. This small, organic molecule acts as either a proton or electron donor, and is used up in the course of every individual reaction. Providing new cofactors every time the synthetic reaction is conducted would be very expensive on a large scale, and as such, it would not be financially viable. As a result, the project team had to find a way of using electricity and the same reaction principles to regenerate the cofactor molecules, so that they would be available for further reaction cycles. Ultimately, they hit on the solution of immobilizing another enzyme in the redox hydrogel to act as a recycling module.

Demonstrating CO2 incorporation into crotonyl-CoA

With this new approach combining CO2 reduction, bioelectrocatalytic technology, material chemistry and synthetic biology, the scientists were able to demonstrate the feasibility of the process at a milliliter scale. By enabling regioselective and stereoselective incorporation of CO2 into crotonyl-CoA, the new approach delivered the most complex product ever achieved in the biocatalytic conversion of CO2. The results of the studies were published in 2021 in “Angewandte Chemie,” a scientific journal for applied chemistry, and selected as a “hot paper.”

Modular platform technology

As the electro-biocatalytic reaction system can be extended on a modular basis, it can function as a platform technology. Depending on the target molecule (synthesis product), suitable enzymes can be selected from bioinformatic databases, manufactured using biotechnology, and embedded in the hydrogels. Consequently, the eBioCO2n module can enable the manufacture of various biobased fine chemicals that can be diversified as needed using specific enzyme cascades. This holds great application potential by companies in the pharmaceutical, agrochemical and food industries.


In the next steps, the team aims to complete the scaling and modular expansion of the process. Chemical synthesis based on biocatalytic CO2 fixation is paving the way for a new form of circular economy by offering alternatives to fossil-based raw materials in chemical synthesis processes.

Enzyme reactions are combined for the process: one for provision and regeneration of the cofactor, one for CO2 fixation.
© Fraunhofer/Marc Müller
The enzymes required for CO2 fixation are biotechnologically produced and purified by FPLC for use in the redox-active hydrogel.
In the "glovebox", the functionality of the enzymes is monitored electrochemically in the absence of air.
© Fraunhofer/Marc Müller
In the "glovebox," the researchers investigate the functionality of enzymes electrochemically in the absence of air. The enzyme kinetics calculated on the basis of the measured current flow provide information on the most suitable enzymes for the eBioCO2n process.
Dr. Leonardo Castañeda-Losada at the development of the electro-biocatalytic process for CO2 fixation.
© Fraunhofer/Marc Müller
The enzyme for cofactor regeneration is fixed on the electrode together with the enzymes for CO2 fixation in the redox hydrogel.


In novel bioelectrocatalytic approaches, the functional integration of CO2-fixing enzymes onto electrode materials for the electrosynthesis of stereochemically complex molecules remains to be demonstrated. In this publication, we show the electricity-driven regio- and stereoselective incorporation of CO2 into crotonyl-CoA by an NADPH-dependent enzymatic reductive carboxylation. Co-immobilization of a ferredoxin NADP+ reductase and crotonyl-CoA carboxylase/reductase within a 2,2′-viologen-modified hydrogel enabled iterative NADPH recycling and stereoselective formation of (2S)-ethylmalonyl-CoA, a prospective intermediate towards multi-carbon products from CO2. This approach paves the way for realizing even more complex bioelectrocatalyic cascades in the future.

Leonardo Castañeda-Losada, David Adam, Nicole Paczia, Darren Buesen, Fabian Steffler, Volker Sieber, Tobias J. Erb, Michael Richter, Nicolas Plumeré (2021) Bioelectrocatalytic Cofactor Regeneration Coupled to CO2 Fixation in a Redox-Active Hydrogel for Stereoselective C−C Bond Formation; Angewandte Chemie International Edition 2021, 60, 2–8; https://onlinelibrary.wiley.com/doi/10.1002/anie.202103634

Project information

Project title

eBioCO2n – Electricity-driven CO2 conversion through synthetic enzyme cascades


Project duration

January 2019 – December 2022


Project partners



This work was supported by the Fraunhofer and Max Planck cooperation program.