AN ORIGINAL TRANSESTERIFICATION ROUTE FOR FATTY-ACID ESTER PRODUCTIONFROM VEGETABLE-OILS IN A SOLVENT-FREE SYSTEM

Wax ester production from a long-chain alcohol and methyl ester has be en investigated with an immobilized thermostable lipase (lipozyme IM f rom Novo Nordisk). The transesterification reaction rate was monitored in solvent-free medium that was exclusively composed of the reactants and the enzyme. The transesterification is performed by simply mixing the two substrates in various stoichiometric amounts at a temperature range from 55 to 65 degrees C under constant stirring in the presence of low concentrations of enzyme preparation (0.12 to 2%, w/w), Long-c hain reactants produce waxes of high molecular mass that induce low so lubility and high viscosity. On average, high transesterification yiel ds are obtained (around 95%). Thermodynamic parameters involving subst rate concentration and temperature have also been investigated. The ba lance between optimal working temperature and the molar ratio of subst rates in such a complex medium appears to be 60 degrees C, with a mola r ratio methyl oleate/stearyl alcohol of 1:0.5. Substrate in hibition due to stearyl alcohol has been observed. A study of kinetic parameter s has confirmed these results.