Expression of a novel feruloyl esterase from Aspergillus oryzae in Pichia pastoris with esterification activity

A 783-bp gene (AofaeA) that encodes a novel type A feruloyl esterase (AoFaeA) was amplified from Aspergillus oryzae CICC40186 by reverse transcription-PCR (RT-PCR), and extracellularly expressed in Pichia pastoris GS115. The recombinant A. oryzae feruloyl esterase (re-AoFaeA) was purified and characterized. SDS-PAGE analysis of the purified re-AoFaeA displayed a single protein band with an apparent molecular weight of about 37.0 kDa, larger than the theoretical one (28.14 kDa) of AoFaeA. The re-AoFaeA showed its optimal activity at 50 degrees C and pH 5.0. It was stable at 50 degrees C or below for 6 h, and at a pH range of 4.0-6.0. Its activity was not significantly influenced by an array of metal ions tested and EDTA, but inhibited by Cu2+. The K-m and V-max of re-AoFaeA, toward methyl ferulate, were 0.81 mM and 82.2 U/mg, respectively. The esterification yield of ferulic acid with glycerol by re-AoFaeA (200 U/g ferulic acid) reached 60.3%. In addition, 47.8% of the total alkali-extractable ferulic acid in wheat bran was released by synergistic action of re-AoFaeA (50 U/g wheat bran) with a recombinant A. oryzae GH family 11 xylanase(re-AoXyn11A, 600 U/g wheat bran), which was about 11.7-fold higher than that (4.1%) by re-AoFaeA alone. (C) 2014 Elsevier B.V. All rights reserved.