Operational Stability, Regenerability, and Thermodynamics Studies on Biogenic Silica/Magnetite/Graphene Oxide Nanocomposite-Activated Candida rugosa Lipase

Inorganic biopolymer-based nanocomposites are useful for stabilizing lipases for enhanced catalytic performance and easy separation. Herein, we report the operational stability, regenerability, and thermodynamics studies of the ternary biogenic silica/magnetite/graphene oxide nanocomposite (SiO(2)/Fe(3)O(4)/GO) as a support for Candida rugosa lipase (CRL). The X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), field-electron scanning electron microscopy (FESEM), vibrating sample magnetometry (VSM), and nitrogen adsorption/desorption data on the support and biocatalyst corroborated their successful fabrication. XPS revealed the Fe(3)O(4) adopted Fe(2+) and Fe(3+) oxidation states, while XRD data of GO yielded a peak at 2θ = 11.67°, with the SiO(2)/Fe(3)O(4)/GO revealing a high surface area (≈261 m(2)/g). The fourier transform infrared (FTIR) spectra affirmed the successful fabricated supports and catalyst. The half-life and thermodynamic parameters of the superparamagnetic immobilized CRL (CRL/SiO(2)/Fe(3)O(4)/GO) improved over the free CRL. The microwave-regenerated CRL/SiO(2)/Fe(3)O(4)/GO (≈82%) exhibited higher catalytic activity than ultrasonic-regenerated (≈71%) ones. Lower activation ([Formula: see text] and higher deactivation energies ([Formula: see text] were also noted for the CRL/SiO(2)/Fe(3)O(4)/GO (13.87 kJ/mol, 32.32 kJ/mol) than free CRL (15.26 kJ/mol, 27.60 kJ/mol). A peak at 4.28 min in the gas chromatograph-flame ionization detection (GC-FID) chromatogram of the purified ethyl valerate supported the unique six types of 14 hydrogen atoms of the ester (CAS: 539-82-2) in the proton nuclear magnetic resonance ((1)H-NMR) data. The results collectively demonstrated the suitability of SiO(2)/Fe(3)O(4)/GO in stabilizing CRL for improved operational stability and thermodynamics and permitted biocatalyst regenerability.