Comparison and mechanism of CO2 sequestration by different carbonic anhydrase producing bacteria

With the rapid emission of CO₂ accelerating global warming, CO₂ geological storage has attracted wide attention due to its huge storage site and safe long-term storage capacity. Carbonic anhydrase (CA) can accelerate CO₂ hydration reaction and promote calcium carbonate precipitation. However, CA has poor thermal stability and high purification cost, so it is necessary to directly use CA producing bacteria for CO₂ geological storage under high temperature environment. In this paper, CA-producing bacterial strains resistant to medium and high temperature was screened from geological saline aquifers and compared with Bacillus mucilaginosus to reveal the reason for its resistance to medium and high temperature. Subsequently, the CO₂ dissolution sequestration capabilities of the two strains were explored at different temperatures. At 50℃, the CO₂ sequestration capacity of Bacillus licheniformis S5 was the highest, and reached 127 mM after 10 days of reaction, which was 26.8 % and 24.9 % higher than that of B. licheniformis CICC 10101 and B. mucilaginosus. Ultimately, the CO₂ sequestration mechanism of different CA-producing bacteria was analyzed. Under high temperature conditions, the enzyme activity of the unit-living bacteria of B. licheniformis S5 was higher, which was more conducive to the conversion of CO₂ into ionic state. This study provides theoretical support for CO₂ sequestration in some medium and high temperature scenarios.