Abstract
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 (SiO2/Fe3O4/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 Fe3O4 adopted Fe2+ and Fe3+ oxidation states, while XRD data of GO yielded a peak at 2θ = 11.67°, with the SiO2/Fe3O4/GO revealing a high surface area (≈261 m2/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/SiO2/Fe3O4/GO) improved over the free CRL. The microwave-regenerated CRL/SiO2/Fe3O4/GO (≈82%) exhibited higher catalytic activity than ultrasonic-regenerated (≈71%) ones. Lower activation ( and higher deactivation energies ( were also noted for the CRL/SiO2/Fe3O4/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 (1H-NMR) data. The results collectively demonstrated the suitability of SiO2/Fe3O4/GO in stabilizing CRL for improved operational stability and thermodynamics and permitted biocatalyst regenerability.
Highlights
This study examines the influence of biogenic SiO2 /Fe3 O4 /graphene oxide (GO) nanocomposites on the operational stability and thermodynamics of Candida rugosa lipase (CRL)/SiO2 /Fe3 O4 /GO compared to free CRL
The study demonstrates that the fabricated biogenic SiO2 /Fe3 O4 /GO support effecTheimproved study demonstrates the fabricated biogenic
The resultant biocatalyst successfully catalyzed higher yields of Ethyl valerate (EV) compared to free CRL
Summary
The graphene-based magnetic silica nanocomposite combination shows good prospects as a greener and sustainable biopolymer resource This is given the nanocomposite’s ability to stabilize lipases for higher catalytic activity and operational stability, as well as easier separation for recycling [1,2,3]. The ternary chitosan/chitin/Fe3 O4 covalently bound CRL produced 96% pentyl valerate and retained ≈90% initial activity after 40 days of storage [12] Another similar study using lipase conjugated to alginate/nanocellulose/montmorillonite composite produced 92.89% ethyl levulinate in just 6 h. CRL bound on the Fe3 O4 /SiO2 /PAMAM nanocomposite was reusable for seven successive reaction cycles, retaining 68% residual activity [14] Despite these advancements, the technology to fabricate novel ternary nanocomposites for lipase immobilization is still in its infancy. The obtained information could offer new insights into the SiO2 /Fe3 O4 /GO nanocomposite’s feasibility as support for other types of enzymes
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