title: Enzymatic synthesis of galacto-oligosaccharides in an organic-aqueous biphasic system by a novel β-galactosidase from a metagenomic library.
abstract: Prebiotic galacto-oligosaccharides (GOS) were effectively synthesized from lactose in organic-aqueous biphasic media by a novel metagenome-derived β-galactosidase BgaP412. A maximum GOS yield of 46.6% (w/w) was achieved with 75.4% lactose conversion rate in the cyclohexane/buffer system [95:5 (v/v) cyclohexane/buffer] under the optimum reaction conditions (initial lactose concentration = 30% (w/v), T = 50 °C, pH 7.0, and t = 8 h). The corresponding productivity of GOS was approximately 17.5 g L(-1) h(-1). The GOS mixture consisted of tri-, tetra-, and pentasaccharides. Trisaccharides were the chief component of reaction products. These experimental results showed that a low water content, a high initial lactose concentration, and an elevated reaction temperature could significantly promote the transgalactosylation activity of β-galactosidase BgaP412; at the same time, the enhanced GOS yield in an organic-aqueous biphasic system is because of the fact that thermodynamic equilibrium can be shifted to the synthetic direction by reversing the normal hydrolysis.
authors.affiliation: School of Life Sciences, Sun Yat-sen University, Guangzhou, People's Republic of China.
authors.forename: Kui
authors.initials: K
authors.lastname: Wang
authors.forename: Yi
authors.initials: Y
authors.lastname: Lu
authors.forename: Wei Qu
authors.initials: WQ
authors.lastname: Liang
authors.forename: Si Di
authors.initials: SD
authors.lastname: Wang
authors.forename: Yang
authors.initials: Y
authors.lastname: Jiang
authors.forename: Rui
authors.initials: R
authors.lastname: Huang
authors.forename: Yu Huan
authors.initials: YH
authors.lastname: Liu
mesh_terms: D001419:Bacteria / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D055162:Biocatalysis; D005690:Galactose / Q000378:metabolism; D007218:Industrial Microbiology / Q000379:methods*; D007785:Lactose / Q000378:metabolism; D056186:Metagenomics; D009844:Oligosaccharides / Q000096:biosynthesis*; D001616:beta-Galactosidase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D009844:Oligosaccharides; D001616:beta-Galactosidase; D007785:Lactose; D005690:Galactose