Microalgae, the ancient organism capable of performing photosynthesis, are important for life on Earth. Researchers from China and Germany have developed a way to improve microalgae's tolerance to high levels of carbon dioxide, offering new perspectives on cutting carbon emissions and even future exploration of Mars.

Microalgae are fast growing photosynthetic microorganisms that produce about half of the atmospheric oxygen. Microalgae hold potential in carbon dioxide mitigation, biofuel production and wastewater treatment. They can convert atmospheric carbon dioxide into lipids under sunlight and increase the output of algal oil.

However, a major challenge for carbon fixation by microalgae is to improve their tolerance to high levels of carbon dioxide. In flue gases, for instance, the high concentration of carbon dioxide inhibits the growth of microalgae.

During the early days of Earth, the atmospheric level of carbon dioxide was many times higher than today. Over millions of years of evolution, the mechanism that allows microalgae to sense extracellular carbon dioxide gradually adapted to lower and lower levels of the gas.

In the study published on Metabolic Engineering, researchers from the Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences and Ruhr University in Germany tried to rewind the evolutionary clock, returning today's microalgae to its ancient form which can tolerate high levels of carbon dioxide.

The researchers found that an enzyme named CA2 is a key sensor of the extracellular carbon dioxide level in microalgae. By knocking out certain genes, they reduced the activity of CA2 in industrial oil-producing microalgae called Nannochloropsis.

As a result, the mutant microalgae grew 30 percent faster than the original ones in flue gas with 5 percent of carbon dioxide.

The researchers said the study provides perspectives for the development of industrial oil-producing microalgae to convert flue gas to biofuel.

The discovery may also have implications for mankind's pursuit of a new home in space. On Mars, for instance, the level of atmospheric carbon dioxide is as high as 95 percent. To change the hostile atmosphere to a human-friendly one, microalgae, according to many scientists, might be the right candidate for the job.

Source: Xinhua  March 28, 2019