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Issue 06/2016

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From Science & Research

From Science & Research Bioplastic from flue gas and green electricity BioElectroPlast: New Biocatalyst Uses Carbon Dioxide and Regenerative Power for Low-cost Microbial Electrosynthesis Researchers of Karlsruhe Institute of Technology (KIT) (Karlsruhe, Germany) are working on an efficient and inexpensive method to produce a bioplastics. In the BioElectroPlast project funded by the German Federal Ministry of Research they use microorganisms that produce polyhydroxybutyric acid from flue gas, air, and renewable enegry. The optimized process of microbial electrosynthesis opens up further perspectives for the future production of biofuel or for the storage of power from regenerative sources in the form of chemical products, for instance. The consumer’s wish for sustainable products also increases the demand for bioplastics, for e.g. disposable cups, packages or garbage bags. The BioElectroPlast project coordinated by the Applied Biology Group headed by Professor Johannes Gescher of KIT’s Institute for Applied Biosciences (IAB) focuses on a method to produce bioplastics with a minimum consumption of resources and at low costs. In addition, BioElectroPlast is aimed at using the greenhouse gas carbon dioxide (CO 2 ) as an inexpensive and generally available raw material in the chain of values added and at applying renewable energy. For this purpose, the scientists use a relatively new technology, called microbial electrosynthesis. About six years ago, researchers in the USA for the first time described how certain microorganisms grow on a cathode, bind CO 2 , and use the cathode as the only energy and electron source. A chemical process, by contrast, requires high pressures and temperatures and, hence, a high energy input as well as expensive catalysts. So far, microbial electrosynthesis has been used mainly to produce acetates – salts of acetic acid. “We have optimized the process, such that the microorganisms are supplied with more energy for the production of molecules of higher complexity, e.g. polymers,” Johannes Eberhard Reiner of the IAB explains. “We mix the CO 2 with air. Then, the microorganisms use the oxygen as electron acceptor. This is quite similar to human breathing, where oxygen also serves as electron acceptor. In human beings, however, electrons do not come from a cathode, but are released by metabolization of our food in the cells. Then, they are transferred to the oxygen for energy production.” As biocatalyst, the researchers use a newly isolated microorganism that permanently regenerates itself. Flue gas is applied as CO 2 source. As a result, the concentration of this greenhouse gas is reduced and other sources of organic carbon that are usually applied as biotechnological substrates, such as agricultural products, are not required. Competition with food and feed production is avoided. The electric power needed for the BioElectroPlast process is based on regenerative sources. The German Federal Ministry of Education and Research (BMBF) funds the BioElectroPlast project under its initiative “CO2Plus – Material Use of CO 2 to Broaden the Raw Materials Base”. BioElectroPlast started in September this year and is scheduled for a duration of three years. Apart from the IAB, the KIT project partners are the Chair for Water Chemistry and Water Technology of Professor Harald Horn at the Engler-Bunte Institute (EBI) and the Microbial Bioinformatics Group headed by Dr. Andreas Dötsch at the Institute of Functional Interfaces (IFG). The other partners are the University of Freiburg (Germany) and energy provider EnBW AG (headquartered in Karlsruhe, Germany). EnBW participates in the project to further reduce CO 2 emission of coal combustion as a bridge technology. The researchers plan to test their reactors directly in the coalfired power plant of EnBW in Karlsruhe and to use the exhaust gases produced there. In parallel to the BioElectroPlast project, KIT’s researchers also study the conversion of carbon dioxide into valuable compounds under the industry-funded ZeroCarb FP innovation alliance. Here, the scientists use alternative biocatalysts isolated by them, as the industry partners Südzucker AG and B.R.A.I.N. AG have specified different process requirements and concentrate on other end products. MT 40 bioplastics MAGAZINE [06/16] Vol. 11

From Science & Research Polycarbonate from orange peels and CO 2 Take some orange peels, deprive them of the natural material limonene, oxidize them, and bind them with carbon dioxide: now you’ve got a bio-based plastic material that can be used to produce environmentally friendly functional materials for a vast array of industrial applications at low cost. This eco-friendly all-rounder known as PLimC is now enabling a broad spectrum of high-performance plastics to be manufactured solely on the basis of renewable resources. This was discovered by a research team at the University of Bayreuth (Germany), and the findings were published in the scientific journal Nature Communications. PLimC is a polycarbonate that results from a synthesis of limonene oxide and carbon dioxide. This guarantees that it does not contain the harmful substance Bisphenol A, in contrast to traditional polycarbonates. The new bio-based polymer also has a range of properties that make it attractive for industrial applications: PLimC is hard, extremely heatresistant, transparent, and is thus particularly well-suited for coating materials. “Our new study has now enabled us to significantly extend the findings that we published last year,” explained Prof. Dr. Andreas Greiner, head of the Bayreuth research team. “Using a few concrete examples, we have shown that PLimC is extremely well-suited as a base material from which wide-ranging plastics with very specific properties can be developed. For PLimC possesses a double bond that can be strategically utilized for further synthesis.” PLimC One example of such new PLimC-based synthetic materials are antimicrobial polymers that are able to prevent adsorption of E. coli bacteria. As materials for containers used in medical care, they can help decrease risk of infection, for example in hospitals. Such polymers are also expected to contribute to the production of plastic implants with a very low risk of infection. Another example is the water-soluble polymers that dissolve into ecologically harmless elements and then decompose. Such plastics could significantly decrease pollution of our waters by non-soluble plastic particles if they were used to produce bottles, bags, and other containers. PLimC is also a base material for hydrophilic polymers. These in turn have the advantage of having a high level of interaction with water and can therefore be broken down relatively quickly by microorganisms. “If we set about developing new materials on the basis of PLim C, the sky is the limit,” explained Oliver Hauenstein (M.Sc.), who has carried out crucial research on the synthesis and application of this new plastics as part of his doctoral research. “Producing PLimC is easy and extremely eco-friendly. The orange peels disposed of by companies that produce orange juice can be recycled, and the greenhouse gas CO 2 can also be used before it escapes into the atmosphere. In addition, the diverse plastics that can be synthesized on the basis of PLimC without any great technical or financial expenditure are ecologically harmless and recyclable.” MT Publications: [1] O. Hauenstein, S. Agarwal and A. Greiner, Bio-based polycarbonate as synthetic toolbox, Nature Communications 2016, DOI: 10.1038/ ncomms11862 ncomms11862/full/ncomms11862.html [2] O. Hauenstein, M. Reiter, S. Agarwal, B. Rieger and A. Greiner, Biobased polycarbonate from limonene oxide and CO2 with high molecular weight, excellent thermal resistance, hardness and transparency, Green Chem. 2016, 18, 760. DOI: 10.1039/c5gc01694k bioplastics MAGAZINE [06/16] Vol. 11 41

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