Light-powered microbes can help improve the efficiency of target chemical compound production

Researchers found that introducing light dependent proton pump rhodopsin into E. coli can shift the carbon flow from cell metabolism to the production of biosynthetic products. This method of using light as energy can help improve the production efficiency of target compounds and reduce carbon dioxide emissions.

Sharing is the key to social life, whether it is children sharing toys or the country sharing natural resources; But the inevitable fact is that what one side gets more means that the other side gets less. Now, researchers at Osaka University, in cooperation with the University of Shizuoka and Kobe University, have found a way to bypass the need for energy sharing in biological manufacturing, so that the cell pathways that specialize in the production of products can always obtain more energy.

In a recent study published in metabolic engineering, researchers found that microorganisms can be transformed to use light to obtain energy and release cell resources to produce biological products.

Metabolic engineering microorganisms are used to produce various useful chemicals all over the world, but there is a problem: the growth and chemical synthesis of microorganisms require a molecule called ATP as an energy source. Therefore, keeping the cell "factory" healthy will limit the production of chemicals.

Yoshihiro Toya, the first author of the study, explained: "microorganisms that produce useful substances are usually developed by changing metabolism, converting the energy normally used for growth into resources for synthesizing these target substances." "We infer that, on the contrary, we can use light as an external energy source to improve the production of useful substances without destroying the natural metabolism of microorganisms."

To verify this, researchers introduced a heterologous membrane protein called rhodopsin into E. coli, which is a common microorganism in biological manufacturing. Rhodopsin is a light activated pump whose function leads to the production of ATP without the need to use the natural mechanism of the cell (called adenosine triphosphate cycle and respiratory chain) to produce ATP. An additional benefit of this approach is the reduction of carbon dioxide emissions, a by-product of the tricarboxylic acid cycle.

Kiyotaka y. Hara, the project leader, said: "the results clearly show that our strategy is successful." "When exposed to light, rhodopsin expressing cells produce significantly more chemical products, and the carbon flow in these cells shifts from energy production to chemical synthesis."

Once they proved that this concept was applicable to various compounds, such as 3-hydroxypropionic acid, mevalonate and glutathione, the researchers continued to create three new strains of E. coli. The superrhodopsin expressed by one strain has better pump activity than the original rhodopsin tested; This strain was developed by Dr. Toya's team at Osaka University. The other two strains joined the synthetic biological system, which provided the intrinsic supply of the retina (the activator of rhodopsin) and optimized the balanced expression of multiple genes in the relevant metabolic pathways; These strains were established by the team of Dr. Jun Ishii of Kobe University. Finally, Dr. Hara's research team at Shizuoka Prefecture University integrated all these systems into a single strain of E. coli, which produces a chemical substance in a light dependent manner.

Hara said: "our findings show that biomanufacturing microorganisms designed to use light as energy can be used to efficiently biosynthesis useful target compounds."

This new method is expected to improve the efficiency of producing useful materials through fermentation and other biological processes while reducing carbon emissions.

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