Lipase B from the yeast Candida antartica was used to catalyze the enz
ymatic synthesis of fatty acid ascorbyl esters, in 2-methyl-2-butanol
as a solvent. The influence of water activity (a(w)) and reaction medi
um hydrophobicity on the synthesis of 6-O-palmitoyl L-ascorbic acid we
re investigated through a transesterification reaction involving L-asc
orbic acid and palmitic acid methyl ester as substrates. The catalytic
activity of the enzyme and the production at equilibrium were affecte
d by the Do-fixed a(w), best results being obtained far the lowest a,
values. The activation of the lipase was promoted by an increase in th
e methyl palmitate/ascorbic acid molar ratio (R) up to 9, leading to 1
9 g/l of ascorbyl ester after a 5 h reaction time. That performance wa
s not reached in a reaction medium of equal log P level, when methyl p
almitate was partly substituted by a hydrophobic solvent. Results were
applied to the syntheses of polyunsaturated fatty acid ascorbyl ester
s such as ascorbyl eicosapentaenoate, leading to a production range fr
om 11 to 15 g/l, after a 3 h reaction time. (C) 1998 Elsevier Science
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