title: Enzymatic production of lactulose and epilactose in milk.
abstract: The enzymatic production of lactulose was described recently through conversion of lactose by a thermophilic cellobiose 2-epimerase from Caldicellulosiruptor saccharolyticus (CsCE). In the current study, we examined the application of CsCE for lactulose and epilactose production in milk (1.5% fat). The bioconversions were carried out in stirred reaction vessels at 2 different temperatures (50 and 8°C) at a scale of 25 mL volume. At 50°C, 2 highly different CsCE amounts were investigated for the time course of formation of lactulose and epilactose. The conversion of milk lactose (initial lactose content of 48.5 ± 2.1 g/L) resulted in a final yield of 57.7% (28.0 g/L) lactulose and 15.5% (7.49 g/L) epilactose in the case of the approximately 9.5-fold higher CsCE amount (39.5 µkat epilactose, 50°C) after 24 h. Another enzymatic lactose conversion was carried out at low 8°C, an industrially relevant temperature for milk processing. Although the CsCE originated from a thermophilic microorganism, it was still applicable at 8°C. This enzymatic lactose conversion resulted in 56.7% (27.5 g/L) lactulose and 13.6% (6.57 g/L) epilactose from initial milk lactose after 72 h. The time courses of lactose conversion by CsCE suggested that first epilactose formed and afterward lactulose via epilactose. To the best of our knowledge, this is the first time that an enzyme has produced lactulose directly in milk in situ at industrially relevant temperatures.
authors.affiliation: University of Hohenheim, Institute of Food Science and Biotechnology, Department of Biotechnology and Enzyme Science, Garbenstr. 25, 70599 Stuttgart, Germany.
authors.forename: Eva
authors.initials: E
authors.lastname: Rentschler
authors.affiliation: University of Hohenheim, Institute of Food Science and Biotechnology, Department of Biotechnology and Enzyme Science, Garbenstr. 25, 70599 Stuttgart, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Schuh
authors.affiliation: University of Hohenheim, Institute of Food Science and Biotechnology, Department of Biotechnology and Enzyme Science, Garbenstr. 25, 70599 Stuttgart, Germany.
authors.forename: Manuel
authors.initials: M
authors.lastname: Krewinkel
authors.affiliation: University of Hohenheim, Institute of Food Science and Biotechnology, Department of Biotechnology and Enzyme Science, Garbenstr. 25, 70599 Stuttgart, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Baur
authors.affiliation: University of Hohenheim, Institute of Food Science and Biotechnology, Department of Biotechnology and Enzyme Science, Garbenstr. 25, 70599 Stuttgart, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Claaßen
authors.affiliation: University of Hohenheim, Institute of Food Science and Biotechnology, Department of Biotechnology and Enzyme Science, Garbenstr. 25, 70599 Stuttgart, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Meyer
authors.affiliation: University of Hohenheim, Institute of Food Science and Biotechnology, Department of Biotechnology and Enzyme Science, Garbenstr. 25, 70599 Stuttgart, Germany.
authors.forename: Beatrice
authors.initials: B
authors.lastname: Kuschel
authors.affiliation: University of Hohenheim, Institute of Food Science and Biotechnology, Department of Biotechnology and Enzyme Science, Garbenstr. 25, 70599 Stuttgart, Germany. Electronic address: t.stressler@uni-hohenheim.de.
authors.forename: Timo
authors.initials: T
authors.lastname: Stressler
authors.affiliation: University of Hohenheim, Institute of Food Science and Biotechnology, Department of Biotechnology and Enzyme Science, Garbenstr. 25, 70599 Stuttgart, Germany.
authors.forename: Lutz
authors.initials: L
authors.lastname: Fischer
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism*; D002238:Carbohydrate Epimerases / Q000378:metabolism*; D004187:Disaccharides / Q000378:metabolism*; D000068536:Bacillota / Q000201:enzymology*; D007792:Lactulose / Q000378:metabolism*; D008892:Milk / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D004187:Disaccharides; C047464:epilactose; D007792:Lactulose; D002238:Carbohydrate Epimerases
keywords: cellobiose 2-epimerase; epilactose; lactulose; milk; prebiotic