Specificity of a lipase in ester synthesis: effect of alcohol

Abstract

Ester synthesis by the Mucor miehei lipase has been studied for various alcohol substrates: n-propanol, n-butanol, isoamyl alcohol, n-hexanol, n-octanol, 2-ethylhex-anol, n-decanol, and lauryl alcohol. The effects of temperature, the nature of the acid, and immobilization of the lipase on its substrate specficity have been elucidated by carrying out esterifications at 29 and 50 °C with lauric and oleic acids and by using both the soluble and immobilized (resin-adsorbed) forms of the lipase as catalysts. Higher synthesis rates were obtained with oleic acid than with lauric acid. A bimodal distribution pattern was observed for the reaction rate as a function of alcohol chain length. Two superimposed "bells" were obtained with maxima at C4 (butanol) and C10 (decanol) at 29 °C. Whereas immobilization of the lipase did not influence this substrate specificity, an increase in temperature to 50 °C caused a shift in the first peak from C4 to C6 (hexanol), while the second peak position was not affected. The minimum, in all cases, was found to be at C8 (octanol).