China News Service, Beijing, April 28 (Reporter Sun Zifa) Can carbon dioxide "change" other things besides "change" starch?
The latest answer given by Chinese scientists is "energy" - it can reduce and synthesize glucose and oil.
Following the de novo synthesis of carbon dioxide to starch for the first time in the world, the Chinese team of scientists once again realized carbon dioxide "turning waste into treasure". They successfully reduced carbon dioxide into high-concentration acetic acid by electrocatalysis combined with biosynthesis, and further utilized microorganisms. Can synthesize glucose and lipids.
This heavy scientific research achievement was jointly completed by Xia Chuan's research group of University of Electronic Science and Technology of China, Yu Tao's research group of Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, and Zeng Jie's research group of University of Science and Technology of China. The journal Nature-Catalysis is published as a cover article.
Grain boundary copper catalyzes the reduction of CO to acetic acid.
Photo courtesy of the research team
Schematic illustration of the conversion of carbon dioxide and water into long-chain products via electrochemically coupled biological fermentation.
Photo courtesy of the research team
Industrial waste gas becomes "vinegar" under mild conditions
How exactly does carbon dioxide turn into glucose and oil in this study?
Zeng Jie Cope said that, first of all, carbon dioxide needs to be converted into raw materials that can be used by microorganisms to facilitate microbial fermentation.
Clean and efficient electrocatalysis technology can work under normal temperature and pressure conditions, which is an ideal choice for realizing this process, and their team has developed many mature electrocatalyst systems for this.
As for which "raw material" to be converted into, the researchers set their sights on acetic acid.
Because it is not only the main component of vinegar, but also an excellent biosynthetic carbon source that can be converted into other biological substances such as glucose.
"The direct electrolysis of carbon dioxide can obtain acetic acid, but the efficiency is not high, so we adopted a 'two-step' strategy - first to obtain carbon monoxide with high efficiency, and then from carbon monoxide to acetic acid." Zeng Jie said.
Xia Chuan pointed out that the acetic acid produced by conventional electrocatalytic devices is mixed with many electrolyte salts and cannot be directly used for biological fermentation.
Therefore, in order to "feed" the microorganisms, it is not only necessary to improve the conversion efficiency and ensure the quantity of "food", but also to obtain pure acetic acid without electrolyte salts to ensure the quality of "food".
The research team used a new solid-state electrolyte reaction device to replace the original electrolyte salt solution with a solid-state electrolyte, and directly obtained a pure aqueous acetic acid solution without further separation.
Using this device, an aqueous solution of acetic acid with a purity of 97% can be continuously prepared for over 140 hours within a stable current density.
Glucose and fatty acids are synthesized from acetate and acetic acid as carbon sources.
Photo courtesy of the research team
Saccharomyces cerevisiae strain engineering.
Photo courtesy of the research team
Microorganisms "jealous" produce glucose
Yu Tao said that after obtaining acetic acid, the research team tried to use the microorganism Saccharomyces cerevisiae to synthesize glucose.
This process is like a microorganism being "jealous". Saccharomyces cerevisiae synthesizes glucose by constantly being "jealous", but in this process, Saccharomyces cerevisiae itself also metabolizes part of the glucose, so the yield is not high.
In this regard, the research team abolished the ability of Saccharomyces cerevisiae to metabolize glucose by knocking out three key enzymatic elements in Saccharomyces cerevisiae that metabolize glucose.
After the knockout, the engineered yeast strain in the experiment produced 1.7 grams of glucose per liter under shake flask fermentation conditions.
To further increase the synthetic glucose production, it is necessary not only to abolish the ability of Saccharomyces cerevisiae, but also to strengthen its own ability to accumulate glucose.
The researchers then knocked out two enzymatic elements suspected of metabolizing glucose, and inserted glucose phosphatase elements from Pantoea and Escherichia coli.
Yu Tao said that these two enzymes can "open a different way" to convert phosphate molecules in other pathways in the yeast into glucose, increasing the yeast's ability to accumulate glucose.
The glucose yield of the modified engineered yeast strain reached 2.2 grams per liter, a 30% increase in yield.
Yeast strain fermentation broth (brown solution) used to prepare glucose after transformation, and prepared glucose (white solution).
Photo courtesy of the research team
Solid Electrolyte Reactor.
Photo courtesy of the research team
Novel catalytic method facilitates production of high value-added compounds
In recent years, with the rapid rise of new energy power generation and the decline in electricity costs, carbon dioxide electroreduction technology has the potential to compete with traditional chemical processes that rely on fossil energy.
Therefore, the high-efficiency electroreduction of carbon dioxide to prepare high value-added chemicals and fuels is regarded by the academic community as one of the important research directions for the construction of future "zero carbon emission" material transformation.
Xia Chuan said that in order to avoid the product limitations of carbon dioxide electroreduction, it is possible to consider coupling the carbon dioxide electroreduction process with biological processes, using electrocatalytic products as electron carriers for subsequent fermentation by microorganisms to synthesize chemical products with long carbon chains for production and life. .
As a living cell factory, microorganisms have the advantage of high product diversity and can synthesize many compounds that cannot be artificially produced or with low artificial production efficiency. They are a very rich "material synthesis toolbox".
Zeng Jie believes that the added value of carbon can be effectively improved by combining electrocatalysis with a new catalytic method of biosynthesis.
The research team will further study the homogeneity and compatibility of the two platforms, electrocatalysis and biofermentation.
In the future, if you want to synthesize starch, make pigments, and produce drugs, you only need to keep the electrocatalytic facilities unchanged and replace the microorganisms used for fermentation.
The research team produced sodium acetate powder in a solid-state electrolyte reactor.
Photo courtesy of the research team
The research team prepared an aqueous acetic acid solution through a solid-state electrolyte reactor.
Photo courtesy of the research team
Provide new technology for artificial semi-synthetic "food"
Li Can, an academician of the Chinese Academy of Sciences and director of the China Catalysis Professional Committee, commented that this latest research work couples artificial electrocatalysis and biological enzyme catalysis, and has developed a new energy-containing chemical small molecule acetic acid from water and carbon dioxide. Yeast microorganisms catalyze a new way of synthesizing high value-added products such as glucose and free fatty acids, providing a new technology for artificial and semi-artificial synthesis of "food".
Deng Zixin, academician of the Chinese Academy of Sciences and director of the State Key Laboratory of Microbial Metabolism at Shanghai Jiao Tong University, believes that this research work opens up a new strategy for the preparation of food products such as glucose by combining electrochemistry with live cell catalysis, and provides a basis for the further development of electricity-driven new agricultural and bio-manufacturing industries. It provides a new paradigm and is an important development direction in carbon dioxide utilization.
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