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Resourcification of greenhouse gases: C1-fixing pathway discovered

A method of converting gases, a cause of climate change, into valuable biochemical substances has been discovered. Gases emitted from factory chimneys, such as carbon dioxide and methane, are known as primary greenhouse gases. C1 gases having one carbon atom, namely, carbon dioxide (CO₂), carbon monoxide (CO), and methane (CH₄) are being extensively studied as they look promising as a new source of energy, depending on the processing method.

The team, led by Professor Byung-Kwan Cho, identified a new pathway that utilizes C1 gases. The proposed pathway is the most efficient among related pathways known to date, and is expected to be useful in industrial applications that convert C1 gases into biochemical substances.

Seventh pathway is most efficient among the C1-fixing pathways

The team, led by Professor Byung-Kwan Cho, discovered a new pathway to convert C1 gases into organic matter. There are six C1-fixing pathways known to date. Before this discovery, the Wood–Ljungdahl pathway in acetogens was found to be the most efficient. Acetogens can thrive in various environments and produce hundreds of billions of kilograms of acetic acid in a year, thus playing a key role in the global carbon cycle. However, they grow at a rate ten times slower than E. coli and other industrial microorganisms, which acts as a limitation during the conversion of C1 gases into valuable biochemical substances.

Using next-generation genome sequencing and genetic analysis, the team established a digital virtual cell model. They predicted the efficiency of C1-fixing pathways, and discovered that a seventh pathway exists. The new pathway was found by coutilizing the Wood–Ljungdahl pathway and glycine synthase pathway to fix C1 compounds, and at the same time, acquire energy needed for cellular growth. The team proved that C1 gas is used in the autotrophic growth of Clostridium drakei via gene expression, isotope-based metabolite-tracing, and genome editing. In addition, C1 gas was found to be rapidly utilized when related genes were introduced in other acetogens having slow growth rates.

“New pathway discovered after countless failures”

Professor Byung-Kwan Cho said, “There is a higher demand for this technology than when I started this study seven years ago, and I feel a greater sense of responsibility. By using the new pathway, we can overcome limitations on the synthesis of biochemical substances caused by the slow growth of acetogens.” The team plans to build upon this study to create intelligent artificial cells.

The study was published in the online version of the Proceedings of the National Academy of Sciences of the United States of America (PNAS) on March 13, 2020.

Prof. Byung-Kwan Cho
2020 KI Annual Report

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