球霰石碳酸钙制备工艺优化及几丁质酶对碳酸钙的影响

为了建立一种以CaCl₂为原料碳化合成高产率高纯度球霰石碳酸钙的工艺。通过单因素考察几丁质酶添加、碳化温度、pH、CaCl₂浓度和碳化时间等工艺条件对钙离子碳化率的影响，再用正交试验优化工艺，并用扫描电镜（SEM）、红外光谱（IR）等表征考察优化条件下几丁质酶对碳酸钙晶型与组成的调控。结果表明，几丁质酶添加基本不影响钙离子碳化率，而碳化温度、pH、CaCl₂浓度和碳化时间等对钙离子碳化率存在显著性影响；35 ℃下，以1 L/min气体流速往pH 12.5的1 mol/L CaCl₂溶液持续通入CO₂碳化6 min，钙离子碳化效果最佳，碳化率达99.88%。SEM和IR等表征结果显示，未加几丁质酶制得由球状颗粒和少部分菱形块状组装形成的直径为2 ~ 8 μm的大小不一的方解石型碳酸钙微球；加入几丁质酶后，菱形块状形貌消失，且随着几丁质酶添加比例增大，碳酸钙微球尺寸逐渐下降；当酶钙质量比为0.01:1时，制备得直径小于1 μm的大小较均一的高纯度蓬松球霰石型碳酸钙微球。结果说明几丁质酶调控下可制备出高产率高纯度球霰石碳酸钙，研究对食药级碳酸钙的仿生制备具有重要意义。

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.