Molecular cages encapsulating lipase and the effect of cage hydrophobicity and cage size

Abstract

To firmly immobilize enzyme on carrier surface without covalent attachment as well as improve enzyme stability, an effective method of enzyme immobilization was developed by encapsulating enzyme into nano-molecular cages on the surface of magnetic microspheres. Compared with physical adsorption, molecular cage encapsulation could fix lipase much more firmly and make lipase more active. Then, this study focused on investigating the effects of cage hydrophobicity and cage size on lipase encapsulation respectively by adjusting the log P value (from −0.85 to 1.28) and chain length (from 2.93 to 5.41 nm) of crosslinkers. It showed that lipase activity was dependent on the hydrophobicity of cage. Moreover, the size of cage had important effect on lipase loading amount, and a big cage was conducive to house lipase molecule. The structural analysis indicated that molecular cages could retain the active conformation of lipase and increase its structural rigidity. Molecular dynamics simulation revealed the interaction between the lid domain of lipase and molecular cage, leading to the higher activity of encapsulated lipase (63.6 U/mg) than that of free lipase (50.6 U/mg). Besides, the encapsulated lipase showed more than twice higher thermal stability and almost 8 times higher tolerance to denaturant than the adsorbed lipase.