title: Characterisation of a novel cellobiose 2-epimerase from thermophilic Caldicellulosiruptor obsidiansis for lactulose production.
abstract: BACKGROUND
  Lactulose, a bioactive lactose derivative, has been widely used in food and pharmaceutical industries. Isomerisation of lactose to lactulose by cellobiose 2-epimerase (CE) has recently attracted increasing attention, since CE produces lactulose with high yield from lactose as a single substrate. In this study, a new lactulose-producing CE from Caldicellulosiruptor obsidiansis was extensively characterised.
  
  
  RESULTS
  The recombinant enzyme exhibited maximal activity at pH 7.5 and 70 °C. It displayed high thermostability with Tmof 86.7 °C. The half-life was calculated to be 8.1, 2.8 and 0.6 h at 75, 80, and 85 °C, respectively. When lactose was used as substrate, epilactose was rapidly produced in a short period, and afterwards both epilactose and lactose were steadily isomerised to lactulose, with a final ratio of 35:11:54 for lactose:epilactose:lactulose. When the reverse reaction was investigated using lactulose as substrate, both lactose and epilactose appeared to be steadily produced from the start.
  
  
  CONCLUSIONS
  The recombinant CE showed both epimerisation and isomerisation activities against lactose, making it an alternative promising biocatalyst candidate for lactulose production. © 2016 Society of Chemical Industry.
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, 214122, China.
authors.forename: Qiuming
authors.initials: Q
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, 214122, China.|University of Hohenheim, Institute of Food Science and Biotechnology, Department of Biotechnology and Enzyme Science, Garbenstr. 25, 70599, Stuttgart, Germany.
authors.forename: Roman
authors.initials: R
authors.lastname: Levin
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, 214122, China.
authors.forename: Wenli
authors.initials: W
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, 214122, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, 214122, China.|Synergetic Innovation Center of Food Safety and Nutrition, Jiangnan University, Wuxi, 214122, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Jiang
authors.affiliation: University of Hohenheim, Institute of Food Science and Biotechnology, Department of Biotechnology and Enzyme Science, Garbenstr. 25, 70599, Stuttgart, Germany.
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
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, 214122, China.|Synergetic Innovation Center of Food Safety and Nutrition, Jiangnan University, Wuxi, 214122, China.
authors.forename: Wanmeng
authors.initials: W
authors.lastname: Mu
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002475:Cellobiose / Q000737:chemistry / Q000378:metabolism*; D004795:Enzyme Stability; D000068536:Bacillota / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007785:Lactose / Q000737:chemistry / Q000378:metabolism; D007792:Lactulose / Q000737:chemistry / Q000378:metabolism*; D019998:Racemases and Epimerases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D002475:Cellobiose; D007792:Lactulose; D019998:Racemases and Epimerases; D007785:Lactose
keywords: Caldicellulosiruptor obsidiansis; cellobiose 2-epimerase; epilactose; isomerisation; lactulose