Carbonic anhydrase-producing microorganisms can rely on their metabolism for carbon sequestration and carbonate precipitation, which is a relatively effective mode among the known microbially induced carbonate precipitation (MICP) methods. A newly carbonic anhydrase-producing strain was isolated from soil samples. 16S rDNA gene sequencing showed this strain had 99.18% sequence identity to Chryseobacterium gambrini. Various culture parameters (temperature, pH, rotational speed, inoculum size, and metal ions) were optimized for optimal microbial growth and CA activities. Optimal culture conditions were as follows: temperature of 30 °C, pH 6-7, rotational speed 150 rpm, and inoculum size 1%. It was observed that Co2+ and Mn2+ can improve CA activity with optimal concentrations of 0.02 mM and 0.01 mM, respectively. Furthermore, the introduction of CO2 for 15 min daily leads to a 36% increase in the final production of biotic CaCO3, reaching 2.884 g/L. Characterization of the mineralization precipitates was conducted to reveal the mechanism of the carbonic anhydrase-producing bacterium. Lastly, an analysis of the crystalline species and content of the biogenic CaCO3 was performed to lay the groundwork for future crystalline adjustments and to offer technical support for the application of the calcium method.
Keywords: CO2 hydration; Carbonic anhydrase; Enzyme activity; MICP.
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