An Enzyme Net Coating the Surface of Nanoparticles: A Simple and Efficient Method for the Immobilization of Phospholipase D

Phospholipase D (PLD) was immobilized in a simple and effective way by adsorption and precipitation of the enzyme, followed by chemical cross-linking to form an “enzyme net” covering the surface of nonporous silicon dioxide nanoparticles. For catalyzing transphosphatidylation to produce phosphatidylethanolamine (PE), at pH 6.0 and 35 °C (the optimum operational conditions), the specific activity of immobilized PLD reached 15872 U/gprotein, which was approximately 1.15 times higher than the maximum value of specific activity of free PLD (13813 U/gprotein). A kinetic study demonstrates immobilized PLD had increases in catalytic activity and enzyme–substrate affinity. In addition, the thermostability and pH tolerance were significantly enhanced compared with free PLD. The half-life of immobilized PLD was significantly increased from 30 to 70 days at 4 °C (approximately 2.3 times). This novel method has been proven to be suitable for the production of robust biocatalysts.