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Immobilized lipase from Candida antarctica (Novozyme 435) was tested for the synthesis of various phenolic acid esters (ethyl and n-butyl cinnamate, ethyl p-coumarate and n-butyl p-methoxycinnamate). The second-order kinetic model was used to mathematically describe the reaction kinetics and to compare present processes quantitatively. It was found that the model agreed well with the experimental data. Further, the effect of alcohol type on the esterification of cinnamic acid was investigated. The immobilized lipase showed more ability to catalyze the synthesis of butyl cinnamate. Therefore, the process was optimized for the synthesis of butyl cinnamate as a function of solvent polarity (logP) and amount of biocatalyst. The highest ester yield of 60.7 % was obtained for the highest enzyme concentration tested (3 % w/w), but the productivity was for 34 % lower than the corresponding value obtained for the enzyme concentration of 1 % (w/w). The synthesized esters were purified, identified, and screened for antioxidant activities. Both DPPH assay and cyclic voltammetry measurement have shown that cinnamic acid esters have better antioxidant properties than cinnamic acid itself.

A feruloyl esterase (StFaeC) produced by Sporotrichum thermophile was purified to homogeneity. The native StFaeC was homodimer with a subunit of M-r 23,000 and pI 3. 1. The enzyme activity was optimal at pH 6.0 and 55 degrees C. The esterase displayed remarkable stability at pH 10.0 and retained 50% of its activity after 133 and 55 min at 55 and 60 degrees C, respectively. Determination of k(cat)/K-m revealed that the enzyme had a broad spectrum of activity against the (hydroxyl) cinnamate esters indicating a type C feruloyl esterase. The enzyme was active on substrates containing ferulic acid ester linked to the C-5 and C-2 linkages of arabinofuranose and hydrolysed 4-nitrophenyl-5-O-trans-fer-uloyl-alpha-L-arabinofuranoside three times more efficiently than 4-nitrophenyl-2-O-trans-feruloyl-alpha-L-arabinofuranoside. Ferulic acid was efficiently released from wheat bran when the esterase was incubated together with xylanase from S. thermophile (a maximum of 41% total ferulic acid released after 1 h incubation). StFacC by itself could release FA but at a level almost 10-fold lower than that obtained in the presence of xylanase. The potential of StFaeC for the synthesis of various phenolic acid esters was examined using as a reaction system a ternary water-organic mixture consisting of n-hexane, 1-butanol and water. Also StFaeC catalyzed the transfer of the feruloyl group to L-arabinose in a similar system using t-butanol, with about a 40% conversion of L-arabinose to feruloylated derivative was achieved. This work is the first example of enzymatic feruloylation of a carbohydrate. (c) 2004 Elsevier Inc. All rights reserved. Enzyme and Microbial Technology

An extracellular feruloyl esterase (FoFAE-I) from the culture filtrates of Fusarium oxysporum F3 was purified to homogeneity by ion-exchange, hydrophobic interaction and gel filtration chromatographies. The protein corresponded to molecular mass and pI values of 31 kDa and 9.5, respectively. The enzyme was optimally active at pH 7.0 and 55 degreesC. The purified esterase was fully stable at pH 7.0-9.0 and temperature up to 30 degreesC. Determination of k(cat)/K-m revealed that the enzyme hydrolysed methyl p-coumarate (MpCA) 4.5, 9, and 239 times more efficiently than methyl caffeate (MCA), methyl ferulate (MFA) and methyl sinapinate (MSA), respectively. The enzyme was active on substrates containing ferulic acid ester linked to the C-5 and C-2 linkages of arabinofuranose but showed preference for the ester at position 2. 4-Nitrophenyl-2-O-trans-feruloyl-alpha-L-arabinofuranoside (NPh-5-Fe-Araf) was hydrolysed 100 times more efficiently than 4-nitrophenyl-5-O-trans-feruloyl-alpha-L-arabinofuranoside (NPh-2-Fe-Araf). Ferulic acid (FA) was efficiently released from destarched wheat bran (DSWB) when the esterase was incubated together with xylanase from Sporotrichum thermophile (a maximum of 92% total ferulic acid released after 4 h incubation). FoFAE-I by itself could release FA but at a level almost five-fold lower than that obtained in the presence of xylanase. The potential of FAE-I for the synthesis of various phenolic acid esters was tested using as a reaction system a surfactantless microemulsions formed in ternary mixture consisting of n-hexane, 1-butanol and water. (C) 2003 Elsevier Inc. All rights reserved. Enzyme and Microbial Technology