## 3 Results and Discussion  
### Analysis of Lipase Adsorption in PST Microspheres  
Lipase immobilized in the gigaporous PST microspheres showed higher activity, stability, reusability, and better kinetic performance than that in the mesoporous PST ones. In order to attain the detailed adsorption behaviors of lipase, PST-300 and PST-14 were used for the real-time adsorption of lipase. Figure 2 showed the adsorption process of lipase in PST-300 and PST-14, including the change of adsorption mass and lipase activity within 120 min. It can be seen from Figure 2a that the adsorption reached equilibrium for lipase in PST-300 after the time point of 30 min and for lipase in PST-14 after the time point of 60 min. From Figure 2b, it can be seen that the initial phase of lipase adsorption (before the time point of 30 min) had great influences on lipase activity. In order to study the adsorption of lipase more elaborately, the experiments were carried out firstly under the condition of low lipase concentration (0.05 mg/mL) and short adsorption time (within 30 min). The adsorption states of lipase in gigaporous and mesoporous microspheres were analyzed comparatively. The changes of adsorption mass, enzyme activity, and specific activity of lipase in PST microspheres with adsorption time are shown as Figure 3, which shows a clear difference between the two types of microspheres. In Figure 3a, the adsorption mass increased rapidly in the first two minutes, and monolayer adsorption mainly occurred in this stage since the enzyme concentration was very low (0.05 mg/mL). For the gigaporous microspheres, the adsorption mass basically maintained a sustained growth from the time point of 2 to 30 min. As for mesoporous microspheres, the adsorption mass increased from 12.2 to 15.6 mg/g (from the time point of 2 to 10 min), and nearly kept stable after the time point of 10 min. Therefore, after the time point of 10 min, the adsorption was mainly multilayer. Figures 4 and 5 were the CLSM images and the change of fluorescence intensity of lipase adsorbed in gigaporous and mesoporous microspheres with the adsorption time. For the gigaporous particles, before the time  
Figure 3: Adsorption of lipase (0.05 mg/mL) into PST microspheres within short time ((**a**) Adsorption mass; (**b**) Lipase activity; (**c**) Specific activity). Specific activity of free CALB: 3.8 U/mg. Figure 2: Adsorption process of lipase (0.05 mg/mL) in PST microspheres within 120 min ((**a**) Adsorption mass; (**b**) Lipase activity). point of 2 min, lipase molecules entered the whole particle and dispersed homogeneously (Figure 4a), while, in the mesoporous particles, most enzymes adsorbed in the shell (Figure 5a). Consistent with the increase of adsorption mass in Figure 3a, after the time point of 2 min, the fluorescence intensity in gigaporous particles exhibited a stable and uniform enhance (Figure 4b-d). As for lipase adsorbed in the mesoporous microspheres, only the fluorescence intensity of shell increased due to the limit of a smaller pore size (Figure 5b-d). The effects of the different adsorption behavior in the carriers with various porous structures were researched. The dramatic difference between their enzyme activities (Figure 3b), especially the specific activities (Figure 3c) gave very interesting results. In the first stage (before the time point of 2 min), the specific activity of lipase immobilized in the gigaporous particles was 1.79 U/mg, and that in the mesoporous particles was only 0.99 U/mg. According to the fluorescence distribution, the specific area of the gigaporous and mesoporous particles, and the area per lipase molecule occupied in ideal state, we calculated the amount of enzyme adsorbed on the unit area of the microspheres, 5.34 \(\times\) 10\({}^{11}\) and 3.12 \(\times\) 10\({}^{10}\), respectively. The amount is far less than the molecule number needed for monolayer adsorption in both type of particles (7.85 \(\times\) 10\({}^{14}\), PST-300; 7.68 \(\times\) 10\({}^{15}\), PST-14, 1/10 diameter).