Heterologous expression of two Aspergillus niger feruloyl esterases in Trichoderma reesei for the production of ferulic acid from wheat bran.

Feruloyl esterase (FAE)-encoding genes AnfaeA and AnfaeB were isolated from Aspergillus niger 0913. For overexpression of the two genes in Trichoderma reesei, constitutive and inductive expression plasmids were constructed based on parental plasmid pAg1-H3. The constructed plasmids contained AnfaeA or AnfaeB gene under the control of glyceraldehyde-3-phosphate dehydrogenase A gene (gpdA) promoter (from A. nidulans) or cellobiohydrolases I (cbh I) gene promoter (from T. reesei), and cbh I terminator from T. reesei. The target plasmids were transferred into T. reesei D-86271 (Rut-C30) by Agrobacterium tumefaciens-mediated transformation (ATMT), respectively. A high level of feruloyl esterase was produced by the recombinant fungal strains under solid-state fermentation, and the cbh I promoter was more efficient than the gpdA promoter in the expression of AnfaeA. The optimum temperatures and pH values were 50 °C and 5.0 for AnFAEA, and 35 °C and 6.0 for AnFAEB. The maximum production levels were 20.69 U/gsd for AnFAEA and 15.08 U/gsd for AnFAEB. The recombinant fungal enzyme systems could release 62.9% (for AnFAEA) and 52.2% (for AnFAEB) of total ferulic acids from de-starched wheat bran, which was higher than the 46.3% releasing efficiency of A. niger 0913. The supplement of xylanase from T. longibrachiatum in the enzymatic hydrolysis led to a small increment of the ferulic acids release.