## 1 Introduction  
Immobilization is one of the most effective approaches to improve the catalytic performance of enzymes. To gain a better performance, the immobilized carriers should be rationally designed and selected. It has been demonstrated that the physical properties of carriers, such as surface morphology [1; 2], particle size [3; 4], and inner porous structures [5; 6; 7; 8] have an important impact on enzyme immobilization. Recently, many porous particles have also exhibited their distinctive performance as immobilized carriers [9; 10]. It is worth noting that the pore size of these conventional carriers usually ranges from a few nanometers to tens of nanometers [11; 12]. In this case, the enzyme penetration in most studies might be limited by the tiny pore size. The effect of pore size on the activity of enzymes has been a controversial issue. Because of the complexity of enzymes, different or even opposite results have been reported [13; 14; 15; 16].  
In our previous work, lipase was immobilized in polystyrene (PST) microspheres with different pore sizes of 14 nm (mesoporous), 100 nm (macroporous), and 300 nm (gigaporous). Fortunately, we found the specific activity of lipase immobilized in gigaporous microspheres was 2.87 times and 1.46 times more than that of mesoporous ones and the free lipase, respectively. In addition, the reusability and the stability of lipase in gigaporous microspheres was improved dramatically compared with those of mesoporous ones [17]. The significance of pore size has been demonstrated in this comparative investigation. Therefore, the reasons of these results and the detailed analysis of enzyme adsorption needed to be researched. There were many reports about the enzyme adsorbed in macroporous microspheres. [PERSON] _et al._ studied the distribution and the molecular structure of lipase adsorbed in microspheres with different pore sizes. The average pore sizes of the carriers were usually 40-100 nm. The results showed that the enzyme is localized in an external shell of the bead [18; 19; 20; 21]. They noticed the influences of pore size on the diffusion--the higher the pores, the better the activity due to the diffusion--however, they did not specialize the adsorption state. In addition, although macroporous microspheres were frequently used in enzyme adsorption, many studies mainly focused on the microspheres with a maximum pore size of 100 nm, which may be restricted by the preparation technology of microspheres. As for other researches about gigaporous microspheres, [PERSON] _et al._ investigated the poly(GMA-_co_-EGDMA) [poly(glycidyl methacrylate-_co_-ethylene glycol dimethacrylate)] microspheres with large pore size (over 300 nm) as the immobilized carriers of lipase. The main conclusions mostly focused on the immobilization and catalysis results [22], yet the effects of the adsorption state were not taken into consideration.  
In this work, lipase B from _Candida antarctica_ was selected as the prototype because of its wide applications. The adsorption time and the initial concentration of lipase were tailored to investigate the adsorption amount and the enzyme activity of lipase in the microspheres more precisely. Moreover, considering the possible effect of the pore curvature, lipase adsorption in microspheres was compared with that on the flat surface. In order to attain the real-time data of lipase adsorbed on flat surface, quartz crystal microbalance with dissipation monitoring (QCM-D) was used to monitor the adsorption process of enzyme molecules on flat surface [23].  
The work carried out on the behaviors of lipase adsorption in the gigapores, in the mesopores, and on the flat surface, which was expected to provide a model for the enzyme immobilization in gigaporous microspheres.