Carbon dioxide is first used as a reagent in industry

For the first time, chemists were able to come up with a method in which carbon dioxide (CO2) in the form of a gas serves as the main reagent for producing a useful chemical. Thus, scientists synthesized methionine – an amino acid that is necessary in large quantities, in particular, in order to produce animal feed. The authors argue that the invented method is suitable for industrial production. The results are reported in the journal Nature Catalysis.

Methionine (C5H11NO2S) is now produced in a six-step process using highly toxic substances such as, for example, hydrogen cyanide (hydrocyanic acid, HCN). One of the intermediate reaction products in this process is methional (C4H8OS), which is also produced by the decomposition of methionine by bacteria. “Based on the idea that microorganisms convert methionine to methional with the release of carbon dioxide, we tried to reverse the process,” explains lead author Arne Skerra of the Technical University of Munich in Germany. “Any chemical reaction is potentially reversible, although it often requires huge pressures and energy costs.”

As part of the study, chemists identified the appropriate parameters for triggering the reverse reaction on an industrial scale and the catalysts required for this. Already in preliminary experiments, the percentage of methionine obtained was unexpectedly high, even at a low pressure of only two atmospheres. Subsequently, the authors concentrated on catalysts, which in this case are organic compounds – proteins.

After several years of experiments on laboratory equipment, the authors were able to achieve a ratio of 40% between the raw material and the reaction product, methionine. In addition, they created a theory that describes this biochemical process. “Compared to photosynthesis, in which nature also biocatalytically uses carbon dioxide as building blocks for organic molecules, our response is elegant and simple,” adds Skerra. “Photosynthesis is based on 14 enzymes and has a yield of about 20%, and our method involves the use of only two enzymes.

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