title: Conversion of orange peel to L-galactonic acid in a consolidated process using engineered strains of Aspergillus niger.
abstract: Citrus processing waste is a leftover from the citrus processing industry and is available in large amounts. Typically, this waste is dried to produce animal feed, but sometimes it is just dumped. Its main component is the peel, which consists mostly of pectin, with D-galacturonic acid as the main monomer. Aspergillus niger is a filamentous fungus that efficiently produces pectinases for the hydrolysis of pectin and uses the resulting D-galacturonic acid and most of the other components of citrus peel for growth. We used engineered A. niger strains that were not able to catabolise D-galacturonic acid, but instead converted it to L-galactonic acid. These strains also produced pectinases for the hydrolysis of pectin and were used for the conversion of pectin in orange peel to L-galactonic acid in a consolidated process. The D-galacturonic acid in the orange peel was converted to L-galactonic acid with a yield close to 90%. Submerged and solid-state fermentation processes were compared.
authors.affiliation: VTT Technical Research Centre of Finland, Espoo, 02044 VTT, Finland.
authors.forename: Joosu
authors.initials: J
authors.lastname: Kuivanen
authors.affiliation: VTT Technical Research Centre of Finland, Espoo, 02044 VTT, Finland.
authors.forename: Hugo
authors.initials: H
authors.lastname: Dantas
authors.affiliation: VTT Technical Research Centre of Finland, Espoo, 02044 VTT, Finland.
authors.forename: Dominik
authors.initials: D
authors.lastname: Mojzita
authors.affiliation: Department of Biochemistry and Molecular Biology, Federal University of Paraná, Curitiba-PR, 81531-990, Brazil.
authors.forename: Edgar
authors.initials: E
authors.lastname: Mallmann
authors.affiliation: Department of Biochemistry and Molecular Biology, Federal University of Paraná, Curitiba-PR, 81531-990, Brazil.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Biz
authors.affiliation: Department of Biochemistry and Molecular Biology, Federal University of Paraná, Curitiba-PR, 81531-990, Brazil.
authors.forename: Nadia
authors.initials: N
authors.lastname: Krieger
authors.affiliation: Department of Biochemistry and Molecular Biology, Federal University of Paraná, Curitiba-PR, 81531-990, Brazil.
authors.forename: David
authors.initials: D
authors.lastname: Mitchell
authors.affiliation: VTT Technical Research Centre of Finland, Espoo, 02044 VTT, Finland.
authors.forename: Peter
authors.initials: P
authors.lastname: Richard
keywords: Aspergillus niger; Citrus processing waste; Consolidated bioprocessing; D-galacturonic acid; L-galactonic acid; Orange peel