Microbially induced calcium carbonate precipitation through CO2 sequestration via an engineered Bacillus subtilis.

Background: Microbially induced calcium carbonate precipitation has been extensively researched for geoengineering applications as well as diverse uses within the built environment. Bacteria play a crucial role in producing calcium carbonate minerals, via enzymes including carbonic anhydrase-an enzyme with the capability to hydrolyse CO₂, commonly employed in carbon capture systems. This study describes previously uncharacterised carbonic anhydrase enzyme sequences capable of sequestering CO2 and subsequentially generating CaCO₃ biominerals and suggests a route to produce carbon negative cementitious materials for the construction industry.

Results: Here, Bacillus subtilis was engineered to recombinantly express previously uncharacterised carbonic anhydrase enzymes from Bacillus megaterium and used as a whole cell catalyst allowing this novel bacterium to sequester CO₂ and convert it to calcium carbonate. A significant decrease in CO₂ was observed from 3800 PPM to 820 PPM upon induction of carbonic anhydrase and minerals recovered from these experiments were identified as calcite and vaterite using X-ray diffraction. Further experiments mixed the use of this enzyme (as a cell free extract) with Sporosarcina pasteurii to increase mineral production whilst maintaining a comparable level of CO₂ sequestration.

Conclusion: Recombinantly produced carbonic anhydrase successfully sequestered CO₂ and converted it into calcium carbonate minerals using an engineered microbial system. Through this approach, a process to manufacture cementitious materials with carbon sequestration ability could be developed.