Immobilized lipase on magnetic chitosan microspheres for transesterification of soybean oil

Biodiesel fuel, produced by transesterification of vegetable oils or animal fats with methanol, is a promising alternative diesel fuel due to the limited resources of fossil fuels and the environmental concerns. An environmentally benign process for the transesterification reaction using immobilized lipase has attracted considerable attention for biodiesel production. In the work, magnetic chitosan microspheres were prepared by the chemical co-precipitation approach using glutaraldehyde as cross-linking reagent for lipase immobilization. The immobilization of lipase onto the magnetic particles was confirmed by magnetic measurements, transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) spectra. Using the immobilized lipase, the conversion of soybean oil to fatty acid methyl esters reached 87% under the optimized conditions of methanol/oil amount-of-substance ratio 4:1 with the three-step addition of methanol, reaction temperature 35 °C, and reaction duration 30 h. Moreover, the immobilized lipase could be used for four times without significant decrease of the activity.