Turning CO₂ into minerals without urea

Bacillus megaterium can mineralise carbon dioxide (CO₂) into calcium carbonate (CaCO₃).

The microorganism is commonly found in soil, freshwater and marine environments or on plant surfaces and can use CO₂ to form CaCO₃, the mineral that forms limestone and marble.

Under high-CO₂ conditions – specifically, at concentrations over 470 times those found in the atmosphere – B. megaterium shifted its metabolic strategy.

Using an enzyme called carbonic anhydrase, it converts CO₂ into bicarbonate, which then reacts with calcium ions to form solid calcite. The researchers have found that 94% of the resulting mineral is derived directly from CO₂, not from nitrogen-based compounds like urea.

‘We know that dozens of bacteria have the potential to mineralise crystals,’ says Dimitrios Terzis, corresponding author at EPFL’s Soil Mechanics Laboratory and co-founder of spin-out Medusoil SA. ‘However, what is unique about our work is that we showcase this can be done by directly using CO₂.’

Principi, researcher at the University of Applied Sciences and Arts of Southern Switzerland adds, ‘The use of C13-labelled urea was key to tracing the origin of the carbon in the mineral, allowing us to quantify the microbial pathways with precision. It’s a great example of how multidisciplinary approaches – bridging microbiology, geochemistry, and materials science – can lead to impactful discoveries’.

Thus the microbe could lead the way to bio-based, carbon-sequestering binders, or conservation-grade materials for building and monument restoration.

Researchers from EPFL’s Soils Mechanics Laboratory, the University of Applied Sciences and Arts of Southern Switzerland (SUPSI) and the EPFL start-up Medusoil SA carried out the work  published in Scientific Reports. Medusoil will continue scale-up trials.