Enzymic synthesis of isoamyl isovalerate using immobilized lipase from Rhizomucor miehei: a multivariate analysis.

Effects of substrate concn., enzyme concn., substrate molar ratio, temp. and incubation time on esterification of isoamyl alcohol and isovaleric acid were investigated using immobilized lipase (Lipozyme IM-20; triacylglycerol lipase, EC 3.1.1.3) from Rhizomucor miehei. The product of this esterification, isoamyl isovalerate, posseses a distinct apple flavour and is useful as a natural flavour compound. Max. yield (>85%) was obtained using 0.75M alcohol, 0.5M acid (ratio 1.5:1) and 10 g/l enzyme at 50C after 144 h in n-hexane. Hydrophobic solvents, such as cyclohexane, hexane and heptane/isooctane, were most suitable for esterification, whereas synthesis was low in solvent-free conditions. Using multivariate analysis, enzyme yield could be predicted at known values of input parameters.