Heterologous Expression and Enzymatic Characterization of Ferulic Esterase from Aspergillus terreus and Its Application in the Preparation of Ferulic Acid

To improve the expression level of ferulic esterase (FAE), the FAE encoding gene from Aspergillus terreus was heterologously expressed in Pichia pastoris. The expression level of FAE in the recombinant strain was (17.38 ± 0.34) U/mL, which was approximately 35 times as high as that of the original strain. The molecular mass of the recombinant A. terreus FAE (rAtFAE) was approximately 39 kDa as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Enzymatic characterization showed that the optimal pH of rAtFAE was 6.0, the optimal reaction temperature was 50 ℃, and the k_cat/K_m values measured with methyl caffeic acid, methyl coumarinate, methyl ferulic acid and methyl sinakoate as substrates were 255, 237, 112.64 and 96.85 L/(mol·min), respectively. The combination of rAtFAE and xylanase showed a good synergistic effect in enhancing the release of ferulic acid from wheat bran up to (1876.45 ± 30.05) μg/g.