Optimization of Preparation Process of Vaterite Calcium Carbonate and Effect of Chitinase on Calcium Carbonate

In order to establish a high-yield and high-purity vaterite calcium carbonate synthesis process, CaCl₂ was used as raw material. The effects of chitinase addition, carbonization temperature, pH, CaCl₂ concentration and carbonization time on the carbonization rate of calcium ions were investigated through the single factor, and orthogonal experiment was used to optimize the process. Scanning electron microscope (SEM) and infrared spectroscopy (IR) were applied to investigate the regulation of chitinase on the crystal form and composition of calcium carbonate under optimized conditions. The results showed that the addition of chitinase rarely affected the calcium ion carbonization rate, while the carbonization temperature, pH, CaCl₂ concentration and carbonization time had significant effects on the calcium ion carbonization rate. At 35 ℃, the gas flow rate was 1 L/min, the 1 mol/L CaCl₂ solution with pH 12.5 was continuously fed with CO₂ for 6 min to carbonize, and the effect of calcium ion carbonization was the best, with a carbonization rate of 99.88%. Characterization results such as SEM and IR showed that 2~8 μm calcite-type calcium carbonate microspheres, which assembled from spherical particles and a small part of diamond-shaped blocks, were obtained without chitinase regulation. After adding chitinase, the diamond-shaped block shape disappeared, and the size of calcium carbonate microspheres gradually decreased as the adding proportion of chitinase increased. The high-purity fluffy vaterite-type calcium carbonate microspheres with diameter of less than 1 μm, were obtained with uniform size when the enzyme calcium mass ratio was 0.01:1. The results indicated that high-yield and high-purity vaterite calcium carbonate could be prepared under the control of chitinase. The research was of great significance for the biomimetic preparation of food and pharmaceutical grade calcium carbonate.