Harnessing Tiny Microbes to Transform Excess Carbon Dioxide into Valuable Resources

Certain microbes can cause illness or spoil food, but others are essential for our survival. These minuscule organisms can also be modified to create specific substances. A recent study published in ACS Sustainable Chemistry & Engineering details how researchers have reengineered one such microbe to help combat greenhouse gases. This microbe absorbs carbon dioxide (CO₂) and produces mevalonate, an important component for pharmaceuticals.

The escalating levels of greenhouse gases in our atmosphere have contributed to global warming. To tackle this issue, significant reductions in greenhouse gas emissions, particularly CO₂, are necessary. Additionally, it’s crucial to eliminate the existing CO₂ still in the atmosphere. Current research is focused on developing methods to capture CO₂, and one promising approach uses microbes. By applying genetic engineering, scientists can alter the natural pathways of these microbes, transforming them into small factories capable of producing various substances, such as insulin.

One candidate for this microbial factory is Cupriavidus necator H16, a bacterium that is known for its ability to grow on minimal resources. It primarily feeds on CO₂ and hydrogen gas, making it an excellent option for capturing and converting these gases into larger compounds. However, while the bacterium’s DNA can be adjusted to create exciting products, it struggles to retain these new genetic instructions over time. More technically speaking, the plasmids (which contain the genetic information) are not very stable. Katalin Kovacs and her team sought to enhance C. necator’s memory of its new instructions to enable the production of valuable carbon-based molecules from CO₂.

The researchers began by modifying the biochemical pathways in C. necator that are responsible for transforming CO₂ into larger six-carbon molecules. The stability of the plasmid was found to be linked to an enzyme known as RubisCo, which is essential for the bacterium’s ability to utilize CO₂. The innovative plasmid was designed so that if a cell could not recall its new instructions, it would also lose the ability to produce RubisCo and ultimately perish. Conversely, those cells that could remember would thrive and multiply, passing the plasmid to their offspring.

In experiments, the newly modified microbes achieved a much higher yield of the six-carbon molecule mevalonate compared to a control strain. Mevalonate serves as a fundamental building block for many compounds in both living organisms and synthetic systems, including cholesterol and various steroid molecules used in pharmaceuticals. Notably, this research has yielded the highest quantities of mevalonate to date from CO₂ or other single-carbon reactants utilizing microbes. The researchers indicate that this improved carbon fixation approach is more economically viable than previous methods involving C. necator and could potentially be applied to other microbial strains as well.

The authors express gratitude for the financial support received from the Biotechnology and Biological Sciences Research Council and the Engineering and Physical Sciences Research Council of the United Kingdom.