Influence and Mechanism of pH and Temperature on Microbial Carbonic Anhydrase Production and Activity in Carbon Sequestration and Self-Healing Concrete

Microbial induction of carbonate precipitation is common in nature, carbonic anhydrase (CA) secreted by microorganisms plays an important role in catalyzing the precipitation of CaCO3 from CO2. This study investigated how pH and temperature regulate microbial CA production, activity, and structure, and further examined their effects on CaCO3 deposition, steel slag carbon sequestration, and concrete crack healing. The results demonstrated that bacteria efficiently produced CA and maintained its activity over a broad range of alkaline pH levels and temperatures, the optimal conditions pH 9 and 30°C facilitated both bacterial CA production and activity by regulating growth and metabolism. Furthermore, pH and temperature modulated CA activity by altering its secondary structure (α-helices, β-turns) and weakening the enzyme’s active center for CO2 at higher pH, which consequently influenced CaCO3 deposition efficiency. The microbial treatment significantly enhanced carbon fixation in steel slag, with an 18.9% carbon sequestration rate at 48 hours, an 8% increase over the control group. In concrete crack-healing tests, the application of alkali-resistant microorganisms restored water permeability resistance to 93.24% of the original concrete after 28 d of healing. Microbial mineralization technology has great potential in steel slag carbon sequestration and self-healing concrete.