Manufacture Bioplastics With Microbes From Flue Gas And Electricity

With the desire of consumers for sustainable products, the demand for bioplastic, for example for disposable cups, packaging or waste bags, is also growing. Researchers at the Karlsruhe Institute of Technology (KIT) are therefore developing a resource-saving and cost-effective process for the production of bioplastics: In the "Bioelectroplast" project funded by the Federal Research Ministry, they use microorganisms that produce the polymer polyhydroxybutyric acid from flue gas, air and electricity from renewable sources. The process of microbial electrosynthesis also opens up new perspectives for the future - for example, to produce biofuels or to store electricity from renewable sources in the form of chemical products.

The project, which is coordinated under the direction of Prof. Johannes Gescher at the Institute for Applied Biosciences (IAB) at KIT, aims at a process for the production of bioplastics that saves resources and saves costs. In addition, "Bioelectroplast" is geared towards using the greenhouse gas CO ₂ as an inexpensive raw material that is available everywhere and integrating renewable energies.

Microorganisms produce polymers

The scientists are building on a relatively new technology - microbial electrosynthesis. Around six years ago, researchers in the United States described how certain microorganisms grow on a cathode, fix CO ₂ and use the cathode as the sole source of energy and electrons. A chemical process, on the other hand, requires high pressures and temperatures, that means a high energy input, as well as expensive catalysts. So far, mostly acetates - salts of acetic acid - have been produced with microbial electrosynthesis.

"We have optimized the process so that we provide the microorganisms with more energy so that they can produce more complex molecules - for example polymers -" explains Johannes Eberhard Reiner from KIT. “To do this, we mix the CO ₂ with air. The microorganisms can then use oxygen as an electron acceptor. This is quite similar to the human breathing process, in which oxygen also serves as a receiver for electrons. In humans, of course, the electrons do not come from a cathode, but are released in the cells by the metabolism of the food we eat and then transferred to oxygen for energy production.”

Reduce greenhouse gases and protect agricultural products

The researchers use a newly isolated microorganism that is constantly regenerating itself as a biocatalyst and use flue gas as a CO ₂ source. In this way, they not only achieve a reduction in greenhouse gases, but also protect other sources of organic carbon, which usually serve as biotechnological substrates, such as agricultural products. This avoids competition for food and feed production. The scientists obtain the electrical energy required for the "Bioelectroplast" process from regenerative sources.

The Federal Ministry of Education and Research (BMBF) supports the project with its initiative "CO ₂ -Plus - Material use of CO ₂ to broaden the raw material base". The project started in September this year and is set to run for three years. In addition to the IAB, partners are the Chair for Water Chemistry and Water Technology by Prof. Harald Horn at the Engler-Bunte Institute (EBI) and the Bioprocess Technology and Biosystems Group headed by Prof. Andreas Dötsch at the Institute for Functional Interfaces (IFG) at KIT, as well as the University of Freiburg and EnBW AG. The researchers want to test their reactors directly in the EnBW coal-fired power plant at the Rheinhafen Karlsruhe and use the power plant's exhaust gases. (kj)