title: The acid tolerant and cold-active β-galactosidase from Lactococcus lactis strain is an attractive biocatalyst for lactose hydrolysis.
abstract: The gene encoding the β-galactosidase from the dairy Lactococcus lactis IL1403 strain was cloned, sequenced and overexpressed in Escherichia coli. The purified enzyme has a tetrameric arrangement composed of four identical 120 kDa subunits. Biochemical characterization showed that it is optimally active within a wide range of temperatures from 15 to 55 °C and of pH from 6.0 to 7.5. For its maximal activity this enzyme requires only 0.8 mM Fe(2+) and 1.6 mM Mg(2+). Purified protein displayed a high catalytic efficiency of 102 s(-1) mM(-1) for lactose. The enzyme stability was increased by immobilization mainly at low pH (from 4.0 to 5.5) and high temperatures (55 and 60 °C). The bioconversion of lactose using the L. lactis β-galactosidase allows the production of lactose with a high bioconversion rate (98 %) within a wide range of pH and temperature.
authors.affiliation: Laboratory for Biocrystallography and Structural Biology of Therapeutic Targets, Bases Moléculaires des Systèmes Infectieux-UMR 5086, CNRS/Université de Lyon 1, Institut de Biologie et Chimie des Protéines-FR3302, 7 Passage du Vercors, 69367, Lyon Cedex 07, France.
authors.forename: Violette
authors.initials: V
authors.lastname: Vincent
authors.forename: Nushin
authors.initials: N
authors.lastname: Aghajari
authors.forename: Noémie
authors.initials: N
authors.lastname: Pollet
authors.forename: Anaïs
authors.initials: A
authors.lastname: Boisson
authors.forename: Samira
authors.initials: S
authors.lastname: Boudebbouze
authors.forename: Richard
authors.initials: R
authors.lastname: Haser
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Maguin
authors.forename: Moez
authors.initials: M
authors.lastname: Rhimi
mesh_terms: D003001:Cloning, Molecular; D020536:Enzyme Activators; D004795:Enzyme Stability; D004800:Enzymes, Immobilized / Q000737:chemistry / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D013294:Lactococcus lactis / Q000201:enzymology* / Q000235:genetics; D007785:Lactose / Q000378:metabolism*; D008970:Molecular Weight; D055503:Protein Multimerization; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D013696:Temperature; D001616:beta-Galactosidase / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D020536:Enzyme Activators; D004800:Enzymes, Immobilized; D011994:Recombinant Proteins; D001616:beta-Galactosidase; D007785:Lactose