Tailoring the hydrophobicity of wrinkled silica nanoparticles and of the adsorption medium as a strategy for immobilizing lipase: An efficient catalyst for biofuel production

Hydrophobic wrinkled silica nanoparticles (WSNs) were obtained by surface functionalization with perfluorodecyltriethoxysilane (PDTES) by chemical vapour deposition (CVD). Surface functionalization was made to design a hydrophobic surface to immobilize lipase in its open active conformation by interfacial activation. Moreover, to modulate the closed/open form equilibrium, favouring the open conformation, n-hexane was added to the water/lipase solution, creating a micro-oily environment. Physicochemical characterization of supports was carried out by solid state Si nuclear Magnetic Resonance (NMR), the Brunauer-Emmett-Teller (BET) method, thermogravimetric (TG) analysis, contact angle (CA) measurement, scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. Three different supports for physical immobilization of lipase were prepared, differing in the degree of hydrophobicity. The effect of the different hydrophobicity and of the addition of n-hexane on the adsorption of lipase was evaluated. The hyperactivation of the best biocatalyst was tested in the hydrolysis and transesterification of sunflower seed oil and compared to free lipase. The reaction yields were 87% and 75% respectively for hydrolysis, and 93% and 56% respectively for transesterification. The results suggest that both the hydrophobicity of the support and the addition of n-hexane favour the adsorption of lipase in the active conformation.