▎ 摘　　要

Recently, biodiesel production has received extensive attention as an alternative energy source to conventional fuel. It is non-polluting fuel and combines environmental friendliness with low toxicity, renewability, and biodegradability. Immobilized lipases have been found emerging catalysts for the synthesis of biodiesel. In the current study, we used lipase Km12 to construct three efficient immobilized enzymes, including lipase@ZIF-8 (LZIF), silica@Lipase@ZIF-8 (SLZIF), and silica@Lipase@ZIF-8/graphene oxide (GSLZIF). The results exhibited that the apparent K-m and k(cat) amounts for these immobilized enzymes were higher than that of the free lipase. The GSLZIF exhibited the maximum lipase activity in the pH 8.0-10, in which the free lipase showed the maximum activity in pH 8.0. GSLZIF showed 4.3-fold more activity than the free lipase after 60 min of incubation at 40 degrees C. This immobilized lipase showed a 17% enhancement in the lipase activity in the presence of 50% of methanol compared to the free lipase. Results showed that the GSLZIF retained 77% of initial protein loading after 10 cycles of reusing. Furthermore, GSLZIF showed 88% biodiesel yield from Terminalia chebula oil after 18-h incubation, whereas the free lipase showed 38% biodiesel yield at the same conditions. Taken together, remarkable improvement of biodiesel production (2.3-fold), higher thermal stability (4.9-fold) and higher k(cat) (3.5-fold) of GSLZIF compared with free lipase are the main results of this research. These results indicated that the GSLZIF has high potential in industrial applications, especially in biodiesel production.