CO mineralization induced by non-urea heterotrophic microorganisms: investigation of CO 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 CO concentration. The results showed that under CO stress, Sporosarcina pasteurii enhanced CO sequestration. When the bacterium was incubated at 30 vol% CO, it enhanced the absorption of headspace CO, 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 CO concentration. Meanwhile, different CO concentrations also have a significant effect on the distribution of calcium carbonate particle size, with higher CO 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 CO, indicating that extracellular polymeric substances (EPS) played an important role in CO mineralization. Besides, the hydration reaction as a mechanism for microbial-induced CO sequestration and bio-mineralization, CA accelerated CO hydration to HCO and reacted with OH and Ca to form CaCO 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 CO mineralization.