Synthesis of ethyl caprylate in organic media using Candida rugosa lipase immobilized on exfoliated graphene oxide: Process parameters and reusability studies

• Immobilization of Candida rugosa lipase on silane functionalized exfoliated graphene oxide.
• Exploitation of immobilized lipase for synthesis of ethyl caprylate.
• Reusability of immobilized lipase for ester synthesis upto 30 cycles.
• Increased catalytic specificity of immobilized lipase in non-aqueous medium.

Present work elucidates a general method for biocompatible modification and functionalization of exfoliated graphene oxide (EGO) via direct reaction of organic silane on the surface of nanosheets. Functionalized EGO’s were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) analysis, Raman spectroscopy and thermal gravimetric analysis (TGA). Modified EGO were employed as a supporting matrix for Candida rugosa lipase immobilization and further applied in the synthesis of flavor ester ethyl caprylate. Various conditions were optimized and maximum ester production was obtained at 40 °C with caprylic acid/ethanol ratio of 0.15:0.1 M using cyclo-octane as a reaction medium. A yield of 85% for ethyl caprylate was observed using lipase immobilized on modified EGO which was higher as compared to that of free lipase. Additionally, the immobilized lipase showed reusability upto 30 cycles retaining 50% of initial activity. Thus, the application of enzyme immobilized on functionalized EGO verifies to be promising system for ester synthesis in non-aqueous environment.