Enzymatic synthesis of short chain citronellyl esters by a new lipase from Rhizopus sp

Abstract

Short chain citronellyl esters were synthesized by a new microbial lipase from Rhizopus sp strain isolated and lipase produced at UNICAMP, Brazil. Direct esterification and transesterification reactions have been performed to produce citronellyl acetate and butyrate in a free-solvent system and with n-hexane in reaction medium. Reaction mixture for direct esterification and transesterification was carried out at 45ºC in equimolar concentration of substrates: acid or ester and alcohol. Only citronellyl butyrate was synthesized by direct esterification with yields from 95 to 100% after 24 hrs. of reaction time, with or without n-hexane. Citronellyl acetate was synthesized by transesterification with ethyl acetate and cytronellol, with yield of 58% after 48 hrs. and 48% of conversion for reaction butyl acetate and cytronellol. The results suggest that the size of the aliphatic chain from acyl donor was importance to conversion rate. Acids with more than two carbons showed to be better substrate for Rhizopus sp lipase. Transesterification reaction showed different behaviour, ester substrate with four carbons was better than six carbon for citronellyl acetate synthesis.