Enhanced sequestration of carbon dioxide into calcium carbonate using pressure and a carbonic anhydrase from alkaliphilic Coleofasciculus chthonoplastes .

CO 2 in the atmosphere is a major contributor to global warming but at the same time it has the potential to be a carbon source for advanced biomanufacturing. To utilize CO 2 , carbonic anhydrase has been identified as a key enzyme. Furthermore, attempts have been made to accelerate the sequestration via pressure. This study aims to combine both approaches to achieve high sequestration rates. The carbonic anhydrase of the alkaliphilic cyanobacterium Coleofasciculus chthonoplastes (cahB1) and bovine carbonic anhydrase (BCA) are introduced into a high-pressure reactor to catalyze the hydration of CO 2 at up to 20 bar. The reactor is filled with a CaCl 2 solution. Due to the presence of Ca 2+ , the hydrated CO 2 precipitates as CaCO 3 . The impact of the carbonic anhydrase is clearly visible at all pressures tested. At ambient pressure a CO 2 sequestration rate of 243.68 kg CaCO3 /m 3 h for cahB1 was achieved compared to 150.41 kg CaCO3 /m 3 h without enzymes. At 20 bar the rates were 2682.88 and 2267.88 kg CaCO3 /m 3 h, respectively. The study shows the benefit of a combined CO 2 sequestration process. To examinate the influence of the enzymes on the product formation, the precipitated CaCO 3 was analyzed regarding the crystalline phase and morphology. An interchange of the crystalline phase from vaterite to calcite was observed and discussed.