Faculty of Food Technology and Biotechnology, University of Zagreb
Abstract
Synthesis of isoamyl acetate, a flavour ester extensively used in food industry, has been carried out in a solvent-free system. In the present study, an attempt has been made to enhance the isoamyl acetate synthesis yield by transesterification of isoamyl alcohol with vinyl acetate using immobilized Rhizopus oryzae NRRL 3562 lipase. In the present synthesis, substrates had no inhibitory effect on immobilized lipase. The effects of various reaction parameters on isoamyl acetate synthesis were studied and maximum conversion was achieved at 16 % (by mass per volume) of immobilized lipase, 40 °C and 200 rpm. Under these conditions, 8-hour reaction time was sufficient to reach a high ester conversion of 95 % with 0.5 mol/L of isoamyl alcohol. The structure of the transesterified product was confirmed by infrared and nuclear magnetic resonance spectroscopic studies. Immobilized lipase had Km and vmax values of 306.53 mmol/L and 99 µmol/(h·g) respectively, for isoamyl acetate synthesis in a solvent-free system.Provedena je sinteza izoamilnog acetata, estera koji se često koristi kao pojačivač okusa u prehrambenoj industriji, u sustavu bez otapala. Pokušao se poboljšati prinos izoamilnog acetata transesterifikacijom s vinilnim acetatom pomoću imobilizirane lipaze izolirane iz soja Rhizopus oryzae NRRL 3562. Pri tome supstrat nije inhibirao imobiliziranu lipazu. Istražen je utjecaj različitih parametara reakcije na sintezu te ustanovljeno da je maksimalna pretvorba postignuta sa 16 % (m/V) imobilizirane lipaze pri 40 °C i 200 rpm. Pri tim je uvjetima nakon 8 sati postignuta 95 %-tna konverzija s 0,5 mol/L izoamilnog acetata. Struktura produkta utvrđena je infracrvenom spektroskopijom i nuklearnom magnetskom rezonancijom. Imobilizirana lipaza imala je Km vrijednost od 306,53 mmol/L i υmax od 99 µmol/(h∙g)
