Comparative Study on Lipases Immobilized onto Bentonite and Modified Bentonites and Their Catalytic Properties

The hydrophobic property and structure of Na-bentonite (Na-bent) were tuned by intercalation with cationic surfactants for lipase adsorption. The adsorption isotherms of lipase on Na-bent and modified bentonites demonstrated Langmuir-type shape, and Na-bent showed higher adsorption efficiency than modified bentonites. The observed overlap of lipase molecules on the support and the interactions between these molecules under high protein loading caused the reduction in the activity of immobilized lipase. The immobilized lipases on modified bentonites (Bent-DTAB-lipase, Bent-CTAB-lipase, and Bent-OTAB-lipase) exhibited higher catalytic activity than that on Na-bent, due to the hydrophobically interfacial activation of modified bentonites toward lipase. The highest catalytic activity and stability were observed on Bent-CTAB-lipase, resulting from the tunable hydrophilic/hydrophobic balance of the support’s surface, while the excessive hydrophobic property showed negative influence on lipase’s catalytic performance. The immobilized lipases onto modified bentonites with hydrophobic property showed higher thermal stability and reusability than Na-bent-lipase.