Synthesis Of Mesoporous Silica Templated By F68 And Its Application In The Immobilization Of Lipase

In acidic conditions, mesoporous silica named MS–100 and MS–130 were synthesized using triblock copolymer F68 as template, TEOS as silica source at different hydrothermal temperature. The samples were characterized by XRD, N2 adsorption–desorption, FT–IR and TEM, the results show that these samples are amorphous mesoporous materials with"ink bottle"pore–like structure. The characters of these samples (MS–100, MS–130) were described as follows: the diameters are 4.7 nm, 4.6nm; the total pore volumes are 0.271 cm3·g–1,0.723 cm3·g–1; specific surface areas are 761.2 m2·g–1,670.1 m2·g–1. The higher the temperature of hydrothermal synthesis, the mesoporous silica has the higher porosity and the more uniform of pore size distribution. These mesoporous materials were used as supports to immobilize the porcine pancreatic lipase, and the immobilized amount can reach 740 mg·g–1g and 760 mg·g–1. The optimum immobilized conditions are at pH = 6 for 6 h. The optimal pH and temperature of the hydrolysis of triacetin for the immobilized PPL are at 8.0 and 45℃, while the free PPL were at 7.0 and 35℃. Immobilized lipases can maintain high activity in a wide range indicating that the immobilized PPL is more stable than free PPL. Due to the disclosure of lipase, the activity of immobilized PPL (MS–100–PPL,MS–130–PPL) have been found to be 50%, 65% of their original activity after the fifth reuse.Mesoporous silicas (MS–1, MS–2, MS–3) with different pore diameter were synthesized by hydrothermal method using triblock copolymer F68 as template, TEOS as silica source, and different amount of TIPB was added into this mixture as expanding agent. These samples were characterized by TEM, XRD, FT–IR, N2 adsorption–desorption experiments, and the results show that these mesoporous silicas are amorphous materials, the addition of swelling agent does not change the crystal structure of mesoporous materials. However, the structure parameters of mesoporous silicas, such as pore size and pore volume will be changed with the increase of swelling agent amount. With the increase in the amount of TIPB, the pore volume increase gradually, while the pore diameters increase to 5.2 nm and reduced to 3.8 nm. These mesoporous silicas (MS–1, MS–2 and MS–3) were used as supports to immobilize PPL, the physical adsorptions of PPL can reach the balance at 18 h, the adsorbed maximum activities are observed at pH = 6 and 6 h for MS–1, MS–2. The immobilized PPLs were characterized by various characterization tools (such as N2 adsorption–desorption, FT–IR, etc.), it is found that the lipase molecules are adsorbed into the channels of MS–1 and MS–2; however, the lipase molecules are only adsorbed near the mouth of MS–3 because of its smaller pore diameter. The optimum pH of hydrolysis of triacetin for the immobilized PPLs is higher than the free PPL, however, the optimum temperature of hydrolysis of triacetin for MS–2–PPL and MS–3–PPL is the same with the free PPL, and only the optimum temperature of hydrolysis of triacetin for MS–1–PPL is higher than the free one. But the immobilized PPLs have excellent adaptability in high temperature. After 5 times reuse, the immobilized enzyme can keep some of the original activity, but the activity of MS–3–PPL decreases rapidly.