title: Production of 1-lactulose and lactulose using commercial β-galactosidase from Kluyveromyces lactis in the presence of fructose.
abstract: Production of 1-lactulose and lactulose using commercial β-galactosidase DSM Maxilact® 5000 in the presence of fructose was investigated. Experiments were performed at 40 °C and pH 7.5. Lactose starting concentration was constantly 250 g/l. A novel transgalactosylation product 1-lactulose was detected besides lactulose. Effects of fructose concentration, reaction time and enzyme concentration on transgalactosylation reactions were discussed. In all reactions, the yield ratio 1-lactulose:lactulose was close to 3:1 due to the regioselectivity of β-galactosidase. The maximum production of 1-lactulose and lactulose was approximately 22 and 8 g/l, respectively, when fructose concentration was increased to 100 g/l. Lactose hydrolysis was significantly retarded since fructose strongly attracted water molecules. Higher enzyme concentration can accelerate transgalactosylation reactions without affecting the maximum production of transgalactosylation products. Fructose was a more preferred galactosyl acceptor than lactose, since the synthesis of galactooligosacchairdes was found to be absolutely inhibited in the presence of fructose.
authors.affiliation: Key Laboratory of Saccharides Chemistry and Biotechnology, Ministry of Education, Jiangnan University, 214122 Wuxi, China.
authors.forename: Xiao
authors.initials: X
authors.lastname: Hua
authors.forename: Ruijin
authors.initials: R
authors.lastname: Yang
authors.forename: Qiuyun
authors.initials: Q
authors.lastname: Shen
authors.forename: Fayin
authors.initials: F
authors.lastname: Ye
authors.forename: Wenbin
authors.initials: W
authors.lastname: Zhang
authors.forename: Wei
authors.initials: W
authors.lastname: Zhao
mesh_terms: D001709:Biotechnology / Q000379:methods*; D005632:Fructose / Q000737:chemistry*; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics; D006031:Glycosylation; D007716:Kluyveromyces / Q000201:enzymology* / Q000235:genetics; D007792:Lactulose / Q000737:chemistry*; D001616:beta-Galactosidase / Q000737:chemistry* / Q000235:genetics
chemical_list: D005656:Fungal Proteins; D005632:Fructose; D007792:Lactulose; D001616:beta-Galactosidase