Fabrication of boehmite films with cage-like pores and their properties as enzyme immobilization supports

The texture of porous films prepared from boehmite nanofibres changed from the lengthwise orientation to the random orientation with the addition of ammonia, and with this change, the shape of the pores in the films turned from slit-like into mesh-like while increasing both the pore size and pore volume. The pore size and volume of the films also increased with an increase in the length of the fibres. When the porous films were used for the immobilization of four lipases with different sizes, the films with the mesh texture exhibited higher immobilization ability than the films with the slit texture. It was found that not only the pore size and volume but also the surface charge and hydroxyl groups are important for the immobilization of enzymes. Among the four lipases used, the lipase with the biggest size (ca. 9.5 nm) was most firmly immobilized on the film with the peak top of pore diameter at 10 nm in the distribution curve, and this immobilized lipase exhibited higher activity in the hydrolysis of 2,3-dimercaptopropanol trilactate than the corresponding native one and was recyclable.