Evaluation of diatomaceous earth as a support for sol–gel immobilized lipase for transesterification

Enzymatic production of biodiesel by triglyceride transesterification is a promising alternative to chemically catalyzed biodiesel production despite the challenges involved with using enzymes. Celite® supported lipase sol–gels were investigated as an option for solving some of the challenges associated with the use of enzymes for biodiesel production addressing such problems as activity, stability and reusability of the enzyme. Three types of Celite® were considered (R633, R632, and R647) and compared to unsupported lipase sol–gels. Various factors were considered with regard to comparing the support materials. They included surface morphology characterized using surface area analysis and scanning electron microscopy, physical properties including adhesion of the sol–gel to the Celite® and the protein loading on the Celite®, and finally enzymatic properties based on the conversion of methanol to methyl oleate and the enzymatic activity of lipase. All the sol–gels showed good conversion and initial lipase activity, and all the Celite® supports had similar sol–gel adhesion and protein loading. Sol–gel immobilized lipase supported on Celite® R632 had an average 6-h percent conversion of approximately 60%, and an average initial lipase activity comparable to that of the unsupported sol–gel formulation.