Amyloid Nano-biofibrils as a New Nano-Scaffold for Lipase Immobilization.

Amyloids could be created under destabilizing conditions from various proteins. Having high chemical reactive groups makes the amyloid fibers suitable for enzyme stabilization. Response surface methodology was used in this study to produce the maximum amounts of amyloid fibrils using Design Expert 7 software. Transmission electron microscopy was also employed to confirm the presence of amyloid fibers. The stabilization process was performed by glutaraldehyde mediated covalent cross-links between the enzyme and amyloid fibers. The optimum conditions for fibrillogenesis were obtained at 4.36 mgml-1 of protein after 72 hours of mild agitation in a mixed citrate-phosphate buffer at the pH of 4.5 and the temperature of 80 ºC. Kinetic parameters including activity, specific activity, optimal pH and temperature and thermal stability of immobilized enzyme were compared with the free counterpart. The kinetic parameters of the immobilized lipase were improved in terms of activity, specific activity, Km and Vmax, optimal pH and temperature and thermal stability at 40 ºC. Amyloid fibrils with a diameter of less than 100 nm, as a new nano-scaffold, increased both the stability of lipase and other kinetic properties of the enzyme. Amyloid fibrils as a new chemically-rich nano-scaffold could be therefore an appropriate matrix for lipase immobilization.