title: Lactulose production by beta-galactosidase in permeabilized cells of Kluyveromyces lactis.
abstract: Lactulose production from lactose and fructose was investigated with several commercial beta-galactosidases. The enzyme from Kluyveromyces lactis exhibited the highest lactulose productivity among the beta-galactosidases tested. The reaction conditions for lactulose production were optimized using cells that had been permeabilized by treatment with 50% (v/v) ethanol: cell concentration, 10.4 g l(-1); concentration of substrates, 40% (w/v) lactose and 20% (w/v) fructose; temperature, 60( degrees )C; pH 7.0. Under these conditions, the permeabilized cells produced approximately 20 g l(-1) lactulose in 3 h with a lactulose productivity of 6.8 g l(-1) h(-1). These results represent 1.3- and 2.1-fold increases in lactulose concentration and productivity compared with untreated washed cells. This is the first reported trial of enzymatic synthesis of lactulose using permeabilized yeast cells.
authors.affiliation: Department of Bioscience and Biotechnology, Sejong University, 98 Gunja-Dong Gwangjin-Gu, 143-747 Seoul, South Korea.
authors.forename: Y-J
authors.initials: YJ
authors.lastname: Lee
authors.forename: C S
authors.initials: CS
authors.lastname: Kim
authors.forename: D-K
authors.initials: DK
authors.lastname: Oh
mesh_terms: D002463:Cell Membrane Permeability; D002851:Chromatography, High Pressure Liquid; D000431:Ethanol; D005632:Fructose; D006863:Hydrogen-Ion Concentration; D007218:Industrial Microbiology; D007716:Kluyveromyces / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D007785:Lactose; D007792:Lactulose / Q000032:analysis / Q000096:biosynthesis*; D013696:Temperature; D013997:Time Factors; D001616:beta-Galactosidase / Q000378:metabolism*
chemical_list: D005632:Fructose; D000431:Ethanol; D007792:Lactulose; D001616:beta-Galactosidase; D007785:Lactose