Society

It’s a step closer to realizing eco-friendly carbon neutrality using microalgae

Improved microalgae that can quickly biosynthesize high value-added substances directly from high concentrations of carbon dioxide emitted from industrial sites have been introduced.

* Microalgae: A generic term for photosynthetic microorganisms. About 2 tons of carbon dioxide can be fixed through 1 ton of microalgae culture.

Professor Shim Sang-Joon (Korea University)’s research team has developed a biological carbon dioxide reduction technology that can quickly convert high concentrations of carbon dioxide harsh on microalgae into high value-added substances such as biofuels.

Microalgae that use carbon dioxide as a carbon source are attracting attention as they can be used to directly produce polymers such as biodegradable plastics, biofuels such as biodiesel, and medicines using carbon dioxide.

However, since microalgae have low resistance to high concentrations of carbon dioxide, there was a limit to efficiently reducing and converting high concentrations of carbon dioxide generated in large quantities throughout the industry. Carbon dioxide resistance is resistance to cytotoxic effects (such as intracellular acidification) caused by high concentrations of CO2. When CO2 resistance increases, even if high concentrations of CO2 in industrial emissions are supplied, CO2 can be efficiently useful without leading to cell death.

The research team found that the low carbon dioxide resistance in microalgae is due to the low expression of amphiphilic hydrogen ion-ATP decomposition enzymes under a high concentration of carbon dioxide environment. Amorphous membrane hydrogen ion-ATP degradation enzymes are one of the hydrogen ion (H+) emission pumps present in the cell amphiphilic membrane and are proteins that play a key role in regulating intracellular acidity (pH) in plants and fungi.

The research team introduced this degradation enzyme gene derived from real plants into microalgae and improved it to continuously express this biological pump. As a result, these microalgae have more than tripled their carbon dioxide resistance to wild microalgae that do not.

This is because the bio pumps smoothly discharged hydrogen ions continuously accumulated in the microalgae as a result of carbon dioxide dissolution and metabolism, thereby maintaining the activity of microalgae even in acidic environments.

The research team also confirmed the effect of improving carbon dioxide resistance through outdoor mass culture experiments. Even when directly exposed to coal combustion gases containing high concentrations of carbon dioxide, it was found to convert carbon dioxide into biomass and biofuel more than twice as fast as wild microalgae.

The research team expects that the developed microalgae strain with increased carbon dioxide resistance can be used as a practical biological high-speed carbon dioxide reduction and conversion technology to realize carbon neutrality in 2050.

Journal Reference: https://www.nature.com/articles/s41467-021-26325-5

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