Virus-like organosilica nanoparticles for lipase immobilization: Characterization and biocatalytic applications

Hydrophobic virus-like organosilica nanoparticles (VOSNs) with a spherical core formed by mesoporous organosilica surrounded by epitaxial perpendicular nanotubes were successfully synthesized for the first time. These hydrophobic VOSNs were used for the immobilization of the lipase B from Candida antarctica (CALB) via covalent binding method, where glutaraldehyde was used as a spacer to form covalent bonds connect between the enzyme and support. Under optimized immobilization conditions, the specific hydrolytic activity which determined via the hydrolysis of p-NPP was 23200 U/g support , and the maximum CALB loading was 115.6 mg/g support . Compared to virus-like silica nanoparticles (VSNs), the hydrophobic VOSNs protected the CALB active conformation from a hazardous external environment due to stronger hydrophobic interactions between the VOSNs and CALB molecule. Thus, compared with CALB@VSNs and free lipase, CALB@VOSNs exhibited better pH, thermal stability, organic solvents tolerance and storage stability. The CALB@VOSNs was used to catalyze the esterification reaction of levulinic acid (LA) and n-lauryl alcohol, which was optimized by a response surface method. Under the optimal conditions (temperature, 51.2 °C; LA: n -lauryl alcohol, 1:11.5; time, 22.6 h), the CALB@VOSNs still retained 75.7% of the LA conversion, whereas the N435 only retained 29.8% of the conversion after 9 cycles. These results showed that hydrophobicity VOSNs could be an efficient support to prepare immobilized enzymes as well as to improve the properties of enzymes.