Sporotrichum thermophile type C feruloyl esterase (StFaeC):: purification, characterization, and its use for phenolic acid (sugar) ester synthesis

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.