title: Enrichment of maize and triticale bran with recombinantAspergillus tubingensisferulic acid esterase.
abstract: Ferulic acid is a natural antioxidant found in various plants and serves as a precursor for various fine chemicals, including the flavouring agent vanillin. However, expensive extraction methods have limited the commercial application of ferulic acid, in particular for the enrichment of food substrates. A recombinantAspergillus tubingensisferulic acid esterase Type A (FAEA) was expressed inAspergillus nigerD15#26 and purified with anion-exchange chromatography (3487 U/mg,Km= 0.43 mM,Kcat= 0.48/min on methyl ferulate). The 36-kDaAtFAEA protein showed maximum ferulic acid esterase activity at 50 °C and pH 6, suggesting potential application in industrial processes. A crudeAtFAEA preparation extracted 26.56 and 8.86 mg/g ferulic acid from maize bran and triticale bran, respectively, and also significantly increased the levels ofp-coumaric and caffeic acid from triticale bran. The cost-effective production ofAtFAEA could therefore allow for the enrichment of brans generally used as food and fodder, or for the production of fine chemicals (such as ferulic andp-coumaric acid) from plant substrates. The potential for larger-scale production ofAtFAEA was demonstrated with theA. nigerD15[AtfaeA] strain yielding a higher enzyme activity (185.14 vs. 83.48 U/ml) and volumetric productivity (3.86 vs. 1.74 U/ml/h) in fed-batch than batch fermentation.
authors.affiliation: Department of Microbiology, Stellenbosch University, Private Bag X1, Matieland, 7602 South Africa.
authors.forename: Eunice N
authors.initials: EN
authors.lastname: Zwane
authors.affiliation: CSIR Biosciences, PO Box 395, Pretoria, 0001 South Africa.
authors.forename: Petrus J
authors.initials: PJ
authors.lastname: van Zyl
authors.affiliation: Department of Food Science, University of Pretoria, Private Bag X20, Hatfield, Pretoria, 0028 South Africa.
authors.forename: Kwaku G
authors.initials: KG
authors.lastname: Duodu
authors.affiliation: Department of Microbiology, Stellenbosch University, Private Bag X1, Matieland, 7602 South Africa.
authors.forename: Shaunita H
authors.initials: SH
authors.lastname: Rose
authors.affiliation: School of Molecular and Cell Biology, University of the Witwatersrand (WITS), Private Bag X3, Wits, 2050 South Africa.
authors.forename: Karl
authors.initials: K
authors.lastname: Rumbold
authors.affiliation: Department of Microbiology, Stellenbosch University, Private Bag X1, Matieland, 7602 South Africa.
authors.forename: Willem H
authors.initials: WH
authors.lastname: van Zyl
authors.affiliation: Department of Microbiology, Stellenbosch University, Private Bag X1, Matieland, 7602 South Africa.
authors.forename: Marinda
authors.initials: M
authors.lastname: Viljoen-Bloom
keywords: Aspergillus niger; Aspergillus tubingensis; Ferulic acid esterase; Maize; Triticale