CO2 mineralization induced by non-urea heterotrophic microorganisms: investigation of CO2 sequestration and mineralization mechanisms.

Carbon capture and sequestration is an effective measure to achieve China's major strategies of carbon peak and carbon neutrality, of which bio-mineralization is an important pathway. Our previous study discovered the microbial mineralization and dust suppression effect based on carbonic anhydrase (CA) in Sporosarcina pasteurii. Based on this, this study further explored the importance of Sporosarcina pasteurii in carbon sequestration by altering CO2 concentration. The results showed that under CO2 stress, Sporosarcina pasteurii enhanced CO2 sequestration. When the bacterium was incubated at 30 vol% CO2, it enhanced the absorption of headspace CO2, increasing by 49.3 %. Meanwhile, the CA activity was also enhanced by adding calcium ions. These results confirmed the mineralization potential of Sporosarcina pasteurii dependent on CO2 concentration. Meanwhile, different CO2 concentrations also have a significant effect on the distribution of calcium carbonate particle size, with higher CO2 concentrations resulting in smaller particles sizes. Furthermore, the transmission electron microscopy (TEM) demonstrated that high electron density particles and extracellular organic matrix secretion were visible internally in the presence of CO2, indicating that extracellular polymeric substances (EPS) played an important role in CO2 mineralization. Besides, the hydration reaction as a mechanism for microbial-induced CO2 sequestration and bio-mineralization, CA accelerated CO2 hydration to HCO3- and reacted with OH- and Ca2+ to form CaCO3 precipitates in an alkaline environment and in the presence of a calcium source. This study provided an important basis for a deeper understanding and advancement of the microbial-mediated bio-mineralization process for efficient CO2 mineralization.