Enzymatic synthesis of butyl butyrate by Candida rugosa lipase supported on magnetized-nanosilica from oil palm leaves: Process optimization, kinetic and thermodynamic study

The present study reports on Candida rugosa lipase (CRL) supported on magnetized nanosilica from oil palm leaves (CRL/Gl-A-SiO2-MNPs) and its utilization in the catalytic synthesis of butyl butyrate. Statistical optimization of process parameters, viz: enzyme loading, incubation time, temperature and substrate molar ratio (1-butanol:n-butyric acid), was executed using the Box–Behnken Design. Under optimized conditions, using 3.5 mg/mL of CRL/Gl-A-SiO2-MNPs, molar ratio of 2:1, incubated at 45 °C a 93.9% yield of ester was achieved in 3 h. CRL/Gl-A-SiO2-MNPs-catalyzed the esterification reaction according to Bi-Bi Ping Pong mechanism. The obtained kinetic values corresponded to Vmax of 0.298 mM/min, as well as Michaelis-Menten constants for substrates, n-butyric acid (KMa) and 1-butanol (KMb) of 17.274 and 13.780 mM, respectively. The values for Kcat, Keff and inhibition constant for 1-butanol (Kib) for the CRL/Gl-A-SiO2-MNPs-catalyzed esterification are 5.109/min, 0.371/min mM−1 and 288.184 mM, respectively. CRL/Gl-A-SiO2-MNPs exhibited higher thermal-stability than the aggregated CRL, as seen in the attained higher values of half-life (45.894 min), D-value (152.45 min), Ed (125 KJ/mol), ΔHd∘ (122.64 KJ/mol) and ΔGd∘ (11.957 KJ/mol) at 70 °C. Storage stability of CRL/Gl-A-SiO2 MNPs was improved by ∼ 9 fold over the aggregated CRL when incubated at room temperature.