This is a machine translation of the original article
中国科学报】凭“空”造淀粉，他们如何把梦想变为现实？
2024-05-22 来源： 中国科学报 刘如楠
[China Science News] Create starch out of thin air. How do they turn their dreams into reality?
2024-05-22 Source: China Science Journal Liu Runan
Starting from Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences (hereinafter referred to as Tianjin Institute of Industrial Biotechnology), walk 4,000 meters southeast and you will come to a place full of “magic”.
This is an engineering test platform, with various instruments placed compactly and the test equipment rumbling. Soon after, the methanol synthesized from carbon dioxide in the fermentation tank will react with specific biocatalysts – enzymes one by one, and eventually turn into tubes of snow-white starch.
Synthetic starch sample.
On September 24, 2021, Tianjin Institute of Engineering and Studies achieved a major breakthrough in the de novo synthesis of carbon dioxide to starch for the first time in the world. The relevant results were published online in “Science”. At the end of 2022, it took another key step from the laboratory to the production line, building a ton-level pilot device and currently testing it.
First “from 0 to 1”, and then “from 1 to 10”, Tianjin Institute of Engineering and Engineering is unswervingly determined and making steady and long-term progress in solving the food problems faced by human development.
1 Is it possible to create starch from “empty space”?
As an important type of polymer carbohydrate, starch is the core product of agricultural civilization, providing humans with the calories needed for survival. For more than 10,000 years, agricultural cultivation was the only way to produce starch.
However, plant photosynthesis has low energy efficiency and long growth cycle, which may cause food security issues. To this end, scientists have explored methods such as hybrid breeding, modular breeding, and molecular breeding, and have also established artificial photosynthetic systems.
“None of this breaks away from the carbon sequestration model of plants. No matter how fast you run, you still rely on your feet. Can you break out of this model and directly build a ‘car’ to put food production on the fast track?” One day in 2014, while on the high-speed train from Beijing back to Tianjin, Ma Yanhe, founding director of Tianjin Institute of Engineering and Biotechnology and chief scientist of the carbon dioxide synthetic starch project, thought this way.
As a scientific research institution dedicated to the development of industrial organisms, Tianjin Institute of Engineering and Biotechnology has always pursued an important goal – to cultivate organisms in industrial workshops and use them to produce agricultural substances, that is, to achieve “agricultural industrialization.”
At a discussion held by the Tianjin Institute of Engineering and Student Affairs, Ma Yanhe continued to think wildly: “We simply imitate plants, synthesize a cell, and let it use carbon dioxide in the air to synthesize the required substances. That is the real ‘out of thin air’ Make whatever you want’!
After careful discussion, everyone agreed that it was too difficult to synthesize cells, but it might be possible to use carbon dioxide to synthesize starch outside the cells.
Ma Yanhe said that the world today is facing a series of major challenges such as climate change, food security, energy resource shortages, and ecological environment pollution, and scientific and technological workers have important responsibilities on their shoulders. The conversion and utilization of carbon dioxide and the industrial synthesis of grain starch are one of the major scientific and technological issues facing challenges.
In January 2015, Cai Tao, an associate researcher at the Tianjin Institute of Engineering and Biotechnology, who was visiting and exchanging at the University of Minnesota in the United States, received a call from Ma Yanhe: “The institute is planning a project to create starch out of thin air.”
“Made out of thin air? Is this possible?” Cai Tao was surprised and excited. At that time, he had joined Tianjin Institute of Technology for more than two years. With the idea of “doing application-oriented basic research”, he switched from traditional biology to synthetic biology research, and went on a study tour in May 2014.
Cai Tao deeply feels that this project is of great significance, but he has been wondering how to do it and whether it can be completed.
Preliminary research results are not optimistic. Even renowned experts in the field shook their heads when they heard about the idea. “Plant photosynthesis has existed for more than a billion years, and the system mechanism has not been fully understood yet. Can you synthesize it from scratch?”
Everyone’s doubts are justified. This is something that has never been done by anyone. After searching through all the literature at home and abroad, I can’t find any clues about the synthesis path and research methods.
“But think about it, why can’t we do what plants can do?” Ma Yanhe said. At that time, the Tianjin Institute of Engineering and Biotechnology had already produced a batch of effective components of medicinal and economic plants such as ginseng, Gastrodia elata, and Rhodiola rosea. Heterologous cell synthesis has designed new biosynthetic routes for sugar, meat, oil, protein, etc., and has accumulated a lot in transforming traditional farming models.
Cai Tao (left) discusses with technical staff.
- Innovate the organizational model and institutionalize scientific research
On January 1, 2016, the Chinese Academy of Sciences’ key deployment project “Artificial Biological Conversion of Carbon Dioxide” was officially launched. This project is led by the Tianjin Institute of Engineering and Student Affairs. It aims to convert carbon dioxide into complex organic matter through the efficient use of chemical energy, light energy, electrical energy and other energy forms. It also allocates part of the funds for the early exploration of “carbon dioxide synthesis of starch” .
Unlike many scientific research organization models that rely on the responsibility system of the project leader, the carbon dioxide synthetic starch project was launched in an institutional manner from the beginning, adopting a three-dimensional scientific research organization model of “overall research department-characteristic research group-platform laboratory”.
The General Research Department is responsible for condensing major scientific and technological tasks and determining research goals around major scientific issues in engineering biology and key core technologies in the bioindustry. Once a project is approved, a senior researcher will serve as the chief scientist, and a “project manager” will be hired throughout the institute and even society.
Subsequently, with the guidance and help of Ma Yanhe and Wang Qinhong, then assistant director of Tianjin Institute of Engineering and Biotechnology, the carbon dioxide synthetic starch project team condensed problems and decomposed tasks according to the project goals, and recruited and organized elite teams from the entire institute to collaboratively tackle key problems.
At the beginning of the project establishment, except for Ma Yanhe, Wang Qinhong, and Cai Tao, the project team only had four main technical personnel responsible for experimental technical work. In a three-year cycle, they will only work on this one project. If necessary, they will contact the research teams inside and outside the institute for cooperation.
When the project officially started, team members felt a lot of pressure. Among the natural reactions of plants, starch synthesis and accumulation involve about 60 steps of metabolic reactions and transport between organelles. For industrial production, these must be simplified while ensuring sufficient and accurate reactions.
To this end, the team collaborated with Ma Hongwu, a researcher at the Tianjin Institute of Engineering and Biotechnology, to develop a new algorithm and systematically mined and screened synthesis paths among 6,568 biochemical reactions to calculate the shortest synthesis route.
This pathway has a total of 9 main reactions. It roughly involves a chemical reaction first, using high-density electricity/hydrogen energy to reduce carbon dioxide to a carbon-one compound, and then a biological reaction to polymerize the carbon-one compound into a carbon-three compound and a carbon-6 compound ( i.e. glucose) up to long chain starch molecules.
But this is just a theoretical virtual path, and it must be turned into reality next.
3 After three years of research, “starch blue” appears for the first time
Synthetic starch research team.
Although the difficulty of the project had been estimated in advance, once the experiment started, the difficulties still exceeded everyone’s imagination.
The most prominent of these is the problem of enzymes. Each step of the reaction requires the participation of enzymes. According to the calculated pathways, many combinations of enzymes have never appeared in reality.
Unlike “one key opens one lock”, the same enzyme can often catalyze multiple reactions, which will cause “side effects”. Sometimes, a substrate is competed by multiple enzymes, resulting in no substrate available for the subsequent enzyme; sometimes, it “hits it off” with the substrate that does not need to be bound, but has “little interest” in the substrate that needs to be bound.
For a long time, team members have been “battling wits” with these enzymes. They worked with the team of Jiang Huifeng, a researcher at the Tianjin Institute of Engineering and Biotechnology who is best at designing new enzymes, and the team of Zhu Leilei, a researcher at the Tianjin Institute of Engineering and Biotechnology who is best at enzyme evolution and transformation, to carry out targeted transformation of existing enzymes, or to design new enzymes from scratch or create unnatural artificial ones. enzymes to solve combinatorial optimization problems of enzymes.
Time came to 2018, and the three-year project was about to come to an end. The team had achieved the synthesis of carbon compounds to starch, but was stuck in the previous step – the reduction reaction from carbon dioxide to carbon compounds.
There were two options available at that time. One was to convert carbon dioxide into formic acid, and then convert formic acid into formaldehyde; the other was to convert carbon dioxide into methanol, and then convert methanol into formaldehyde. But no matter which way, the amount of formaldehyde obtained by the reaction is not enough to support the subsequent reaction.
During those days, team members became extremely sensitive and doubted every step they took, guessing whether the solution was added incorrectly, the dose was not accurate, or other low-level mistakes were made. However, after repeated repetitions, they had to face the fact that there was no error in the operation and the reaction could not advance.
Cai Tao can no longer remember how many times he discussed the formaldehyde reaction amount with Ma Yanhe and You Chun, a researcher at the Tianjin Institute of Engineering and Biotechnology. He gradually found an idea through constant discussions – using the energy generated by “hydrogen combustion” in methanol to drive the reaction that produces formaldehyde and solving the thermodynamic matching problem in the formaldehyde reaction.
On the afternoon of July 24, 2018, Cai Tao was in the conference room upstairs in the laboratory, preparing to participate in the key project stage review meeting of the Chinese Academy of Sciences, when he suddenly received a photo from a laboratory technician. In the photo, three reagent tubes are arranged side by side. The iodine solution in the middle reagent tube containing the latest test product is light blue-purple, which is in obvious contrast with the colorless reagent tubes and dark blue reagent tubes on the left and right sides.
Synthetic starch turns blue when exposed to iodine.
Cai Tao immediately called to confirm. After receiving a positive reply, he was still uneasy and ran all the way back to the laboratory. It wasn’t until he saw the reagent tube with his own eyes that he couldn’t help shouting: “Great! The manufacturing path is finally open!”
That day, everyone’s faces changed from the seriousness they had been in the past few days and were filled with smiles. Cai Tao immediately reported the good news to Ma Yanhe, “This is really the most beautiful color I have ever seen.”
At this point, the de novo synthesis of starch from carbon dioxide has finally achieved “from 0 to 1”, and the synthesis yield has reached 30 mg/L.
- Looking for cooperation outside the institute to welcome the bright moment
The project team did not stop there, but decided to continue to carry out follow-up research and “fight” with the enzyme to improve the synthesis rate and yield.
In the following months, they solved problems such as low activity of the rate-limiting enzyme in the pathway, inhibition of cofactors, and competition for adenosine triphosphate (ATP) through targeted modification of key enzymes.
At the end of 2018, the Chinese Academy of Sciences’ key deployment project “Artificial Biological Conversion of Carbon Dioxide” was completed. The project team increased the starch synthesis output 8 times to 200 to 300 mg/L, far exceeding the initial goal of the project. This means that the carbon dioxide synthetic starch project has ushered in the 2.0 era.
“From the initial ‘blind confidence’, to being hit to the bottom by various difficulties, until version 1.0 and 2.0 were gradually produced, everyone’s confidence was built up bit by bit.” Cai Tao said.
On June 24, 2019, under the guidance of Ma Yanhe, Cai Tao and Jiang Huifeng came to the Dalian Institute of Chemical Physics, Chinese Academy of Sciences (hereinafter referred to as Dalian Institute of Chemical Physics) with the latest progress information to seek cooperation.
At that time, Li Can’s team, an academician of the Chinese Academy of Sciences and a researcher at the Dalian Institute of Chemical Physics, had been working hard for more than 20 years and realized the electrolysis of water to produce green hydrogen, and then synthesized methanol from green hydrogen by adding carbon dioxide. If this pathway can be coupled with the biological reaction pathway for starch synthesis from carbon dioxide, new breakthroughs may be achieved.
After listening to the introduction of the project team, Li Can showed great interest, and the two teams hit it off immediately.
Later, the project team brought the methanol synthesized by Li Can’s team back to the Tianjin Institute of Engineering and Biotechnology laboratory for subsequent starch synthesis experiments. They found that it could be synthesized normally and the reaction rate was the same as that of commercial methanol.
Further adopting the reaction space-time separation strategy to solve the problem of incompatibility between chemical and biological reactions and establishing a biochemical cascade reaction system, the project team increased the starch synthesis output 17 times to 1.6 g/L, achieving controllable synthesis of different types of starch.
Version 3.0 of carbon dioxide synthesis of starch has appeared, and the starch synthesis rate of this artificial pathway significantly exceeds the synthesis rate of corn starch.
On September 24, 2021, “Science” magazine published this result online. The team’s six years of technical research finally yielded fruitful results.
After the results were released, it immediately ignited academic circles and public opinion, and “carbon dioxide synthesis of starch” quickly became a hot topic.
Domestic and foreign experts have said that this achievement is a “typical original breakthrough from 0 to 1”; it is a major breakthrough in the frontier research field of expanding and improving the ability of artificial photosynthesis, and is of “outstanding” significance; not only for the future Agricultural production, especially food production, has a revolutionary impact and is a milestone in the development of the global biomanufacturing industry.