Candida antarctica lipase B-catalysed synthesis of dihydroxyacetone fatty acid esters

The enzymatic syntheses of 1-lauroyl-dihydroxyacetone and 1,3-dilauroyl-dihydroxyacetone were investigated. Lipase B from Candida antarctica (SP435) was used to catalyse the acylation of dihydroxyacetone (DHA) with lauric acid in organic solvent media at controlled water activity. High conversions of dihydroxyacetone (> 90%) are achieved when the water activity is 0.11 or below in solvents of various hydrophobicities, such as diethyl ether, methyl-tert-butyl ether (MTBE) and diphenyl ether. The main product in the esterification of DHA with lauric acid is 1-lauroyl-DHA, while the amount of 1,3-dilauroyl-DHA that is produced can be increased by changing the reaction conditions. Thus, decreasing the water activity from 0.75 to 0.06 resulted in an increase in the total yield of 1,3-dilauroyl-DHA from 3% to 20%. Solvents which have high log P values favoured the acylation of 1-lauroyl-DHA and thereby the formation of 1,3-dilauroyl-DHA. Thus, when diphenyl ether was used in this reaction, the yield of 1,3-dilauroyl-DHA was 45%. Complete acylation to 1,3-dilauroyl-DHA was achieved when a fatty acid vinyl ester was used as acyl donor in a closed reactor.