Study of support materials for sol-gel immobilized lipase

A variety of support materials for sol-gel immobilized lipase were considered based on their ability to provide superior sol-gel adhesion, load protein, and synthesize methyl oleate. A standard approach was developed to formulate the supported lipase sol-gels and to allow comparison of the resulting hybrid materials. These supported sol-gels are proposed as an alternative immobilization regime to overcome some challenges associated with enzymatic biodiesel production such as enzyme stability and cost. The support materials considered were 6-12 mesh silica gel, Celite (R) R633, Celite (R) R632, Celite (R) R647, anion-exchange resin AG3-X4, and Quartzel (R) felt. Each support material exhibited unique properties that would be beneficial for this application including: Quartzel (R) felt had the highest initial sol-gel capacity (62.5 mL/g) and sol-gel adhesion (1100 mg sol-gel/g material); silica gel had the most uniform coating of deposited sol-gel; the anion-exchange resin AG3-X4 supported sol-gel had the highest protein loading (1060 mu g lipase/g) and reaction rate [1.25 mM/(min g-material)]; the Celite (R) support series were the most thermally stable and had the lowest water content; and the Celite (R) R632 supported lipase sol-gels had the highest 6 h biodiesel conversion per gram of supported material (68%) and enzymatic activity [9.4 mmol/(min g-lipase)]. The supported sol-gels with the highest enzymatic properties (conversion, activity, and reaction rate) were those supported on Celite (R) R632, anion-exchange resin AG3-X4, and Quartzel (R). These supported sol-gels had superior performance in comparison with the unsupported sol-gels. Based on this study, the lipase sol-gel support material with the most potential for biodiesel production is Celite (R) R632.