Schematic diagram of synthetic high-energy long-chain food molecules of carbon dioxide in vitro. Courtesy of the research team
Beijing, April 28 (China News Network) (Reporter Sun Zifa) In addition to "changing" starch, can carbon dioxide also "change" other things? The latest answer given by Chinese scientists is "energy" - can reduce the synthesis of glucose and oil.
Following the international first realization of carbon dioxide to starch de novo synthesis, the Chinese team of scientists once again realized carbon dioxide "waste into treasure", they through electrocatalytic combination of biosynthesis, successfully reduced carbon dioxide into high concentration of acetic acid, further use of microorganisms can synthesize glucose and oil.
This blockbuster scientific research achievement was jointly completed by the Xia Chuan Research Group of the University of Electronic Science and Technology of China, the Yu Tao Research Group of the Shenzhen Institute of Advanced Technology of the Chinese Academy of Sciences and the Zeng Jie Research Group of the University of Science and Technology of China, and on the night of April 28, Beijing time, the research paper was published in the form of a cover article in the international professional academic journal "Nature-Catalysis".
Grain boundary copper catalyzes CO reduction to acetic acid. Courtesy of the research team
Schematic of the conversion of carbon dioxide and water into long-chain products through electrochemically coupled biological fermentation. Courtesy of the research team
Industrial exhaust gases become "vinegar" under mild conditions
In this study, how exactly did carbon dioxide become glucose and fat?
Zeng Jieke said that first of all, it is necessary to convert carbon dioxide into raw materials for microbial use to facilitate microbial fermentation. The clean, efficient electrocatalytic technology, which can operate at room temperature and pressure, is ideal for this process, and the team has developed many mature electrocatalyst systems.
As for what kind of "raw material" to convert, the researchers set their sights on acetic acid. Because it is not only the main ingredient in vinegar, but also an excellent biosynthetic carbon source that can be converted into other biological substances such as glucose.
"Direct electrolysis of carbon dioxide can obtain acetic acid, but the efficiency is not high, so we adopt a 'two-step' strategy - first efficiently obtain carbon monoxide, 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" 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 electrolyte reaction device to use a solid electrolyte instead of the original electrolyte salt solution, and directly obtained a pure aqueous acetic acid solution without further separation. Using this device, an aqueous acetic acid solution of 97% purity can be continuously prepared for more than 140 hours within a stable current density.
Synthesis of glucose and fatty acids from acetate and acetic acid as carbon sources. Courtesy of the research team
Engineering modification of Saccharomyces cerevisiae strains. Courtesy of the research team
Microorganisms "eat vinegar" to 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, like microorganisms in the "vinegar", Saccharomyces cerevisiae by constantly "eating vinegar" to synthesize glucose, but in this process, Saccharomyces cerevisiae itself will also metabolize a part of the glucose, so the yield is not high.
In response, the research team abolished the ability of Saccharomyces cerevisiae to metabolize glucose by knocking out three key enzyme elements in Saccharomyces cerevisiae that metabolize glucose. After knockout, the engineered yeast strains in the experiment produced 1.7 grams per liter of glucose under the condition of shaker fermentation.
In order to further increase the production of synthetic glucose, it is necessary not only to abolish the ability of Saccharomyces cerevisiae, but also to strengthen its own ability to accumulate glucose. So the researchers knocked out two enzyme elements suspected of having the ability to metabolize glucose, and inserted glucose phosphatase elements from Ubiquitous and E. coli.
Yu Tao said that these two enzymes can "find another way" to convert phosphoric acid molecules in other pathways in yeast into glucose, increasing the yeast's ability to accumulate glucose. The modified engineered yeast strain produced 2.2 grams of glucose per liter, increasing yield by 30 percent.
The fermented broth of the yeast strain used to prepare glucose after modification (brown solution) and the prepared glucose (white solution). Courtesy of the research team
Solid electrolyte reactor. Courtesy of the research team
New catalytic methods facilitate the 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 electroretrovironment technology has the potential to compete with traditional chemical processes that rely on fossil energy. Therefore, the process of efficient carbon dioxide electroreverting to prepare high value-added chemicals and fuels is considered by the academic community to be one of the important research directions for the construction of future "zero carbon emission" substance conversion.
Xia Chuan said that in order to avoid the limitations of carbon dioxide electroretroduction products, it is possible to consider coupling the carbon dioxide electroretrix process with the biological process, using the electrocatalytic product as an electronic carrier for microbes to subsequently ferment and synthesize long carbon chain chemical products for production and life.
As a living cell factory, the advantage of microorganisms is that the product diversity is very high, and it can synthesize many compounds that cannot be artificially produced or have low artificial production efficiency, and it is a very rich "substance synthesis toolbox".
Zeng Jie believes that the new catalytic method of electrocatalysis combined with biosynthesis can effectively improve the added value of carbon. The research team will further study the homocompatibility and compatibility of the two platforms of electrocatalysis and biological fermentation. In the future, if you want to synthesize starch, manufacture pigments, produce drugs, etc., you only need to keep the electrocatalytic facilities unchanged, and replace the microorganisms used for fermentation.
The research team prepared a sodium acetate powder by a solid electrolyte reactor. Courtesy of the research team
An aqueous solution of acetic acid prepared by the research team by a solid electrolyte reactor. Courtesy of the research team
Provide new technologies for artificial semi-synthetic "grain"
Li Can, an academician of the Chinese Academy of Sciences and director of the China Catalysis Professional Committee, commented that this latest research work coupled with artificial electrocatalysis and biological enzyme catalysis processes, and developed a new way from water and carbon dioxide to small molecules of acetic acid containing energy chemistry, and then engineering modified yeast microorganisms to catalyze the synthesis of high value-added products such as glucose and free fatty acids, providing a new technology for artificial and semi-artificial synthesis of "grain".
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 the research work has opened up a new strategy for the catalytic preparation of glucose and other grain products by electrochemical combination with living cells, which provides a new paradigm for the further development of new agriculture and bio-manufacturing based on electricity, and is an important development direction for carbon dioxide utilization. (End)