ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Chemically modified nanoparticles from oil palm ash silica-coated magnetite as support for Candida rugosa lipase-catalysed hydrolysis: kinetic and thermodynamic studies

Winny Kai Li Wong, Roswanira Abdul Wahab, and Emmanuel Onoja

Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, Johor Bahru, Malaysia

E-mail: roswanira@kimia.fs.utm.my

Received: 11 August 2019  Accepted: 21 October 2019

Abstract:

Herein, silica (SiO₂) extracted from treated oil palm leaves ash (TOPLA) was coated over Fe₃O₄ (SiO₂–Fe₃O₄) before surface modification using 3-aminopropyltriethoxysilane (AP–SiO₂–Fe₃O₄). The AP–SiO₂–Fe₃O₄ was further modified with glutaraldehyde for the chemical immobilisation of Candida rugosa lipase (CRL) on the surface of G–AP–SiO₂–Fe₃O₄ (CRL/G–AP–SiO₂–Fe₃O₄). Surface analytical techniques (FTIR, TGA, and XRD) that monitored the successive processes to prepare the CRL/G–AP–SiO₂–Fe₃O₄ biocatalyst affirmed that CRL (14.7 mg/g, 183 U/g activity) was present on the support. Under an optimized condition, CRL/G–AP–SiO₂–Fe₃O₄ (40 °C, pH 8.0 at 200 rpm) and free CRL (35 °C, pH 7.0, 200 rpm) hydrolysed 98.5% olive oil at fixed 2.5:1 olive oil: water ratio, enzyme load 1.0 mg/mL, signifying retention of lipase activity after immobilisation. Despite the lower V_max (833.3 μmol/mL min), CRL/G–AP–SiO₂–Fe₃O₄ (K_m 0.583 g/mL) showed a 12-fold higher affinity for the substrate over free CRL (K_m 6.00 g/mL, V_max 3330 μmol/mL min). Thermodynamic data also corroborated the increased thermal stability of CRL/G–AP–SiO₂–Fe₃O₄ (t_1/2 38.94 min, D value 129.4 min, ( Delta H_{ ext{d}}^{^circ } ) 110.10–110.27 kJ/mol, ( Delta S_{ ext{d}}^{^circ } ) 292.3–293.2 kJ/mol) over free CRL (t_1/2 23.89 min, D value 79.67, ( Delta H_{ ext{d}}^{^circ } ) 87.55–87.72 kJ/mol, and ( Delta S_{ ext{d}}^{^circ } ) 233.5–233.7 kJ/mol).

Keywords: Silica; Candida rugosa lipase; Nanoparticles; Magnetite; Hydrolysis; Oil palm leaves ash

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-019-00976-7

Chemical Papers 74 (4) 1253–1265 (2020)