Preparation of cross-linked lipase-coated micro-crystals for biodiesel production from waste cooking oil.

A dual modification procedure composed of cross-linking and protein coating with K(2)SO(4) was employed to modify Geotrichum sp. lipase for catalyzing biodiesel production from waste cooking oil. Compared to single modification of protein coating with K(2)SO(4), the dual modification of cross-linking and lipase coating improved catalytic properties in terms of thermostable stability, organic solvent tolerance, pH stability and operational stability in biodiesel production process, although biodiesel yield and initial reaction rate for CLPCMCs were not improved. After five successive batch reactions, CLPCMCs could still maintain 80% of relative biodiesel yield. CLPCMCs retained 64% of relative biodiesel yield after incubation in a pH range of 4-6 for 4 h, and 85% of relative biodiesel yield after incubation in a range of 45-50 °C for 4 h. CLPCMCs still maintained 83% of relative biodiesel yield after both treated in polar organic solvent and non-polar organic solvent for 4 h.