title: Characterization of the cross-linked enzyme aggregates of a novel β-galactosidase, a potential catalyst for the synthesis of galacto-oligosaccharides.
abstract: A novel β-galactosidase (Bgal1-3) was isolated from a marine metagenomic library and then its cross-linked enzyme aggregates (CLEAs) were prepared. The enzymatic properties of Bgal1-3-CLEAs were studied and compared with that of the free enzyme. The thermostability and storage stability of Bgal1-3 were significantly improved after it was immobilized as CLEAs. The galactose-tolerance of the enzyme was also enhanced after the immobilization, which could relieve the inhibitory effect and then tends to be beneficial for the galacto-oligosaccharides (GOS) synthesis. Moreover, higher GOS yield was achieved (59.4 ± 1.5%) by Bgal1-3-CLEAs compared to the free counterpart (57.1 ± 1.7%) in an organic-aqueous biphasic system. The GOS content and composition of the syrups synthesized by the free enzyme and Bgal1-3-CLEAs were similar and they both contained at least seven different oligosaccharides with the degree of polymerization (DP) ranging between 3 and 9. Furthermore, Bgal1-3-CLEAs maintained 82.1 ± 2.1% activity after ten cycles of reuse; the GOS yield of the tenth batch was 52.3 ± 0.3%, which was still higher than that of the most former reports. To the best of our knowledge, this is the first report on the GOS synthesis using CLEAs of β-galactosidase in an organic-aqueous biphasic system. The study not only further expands the application scope of CLEA, but also provides a potential catalyst for the synthesis of GOS with low cost.
authors.affiliation: School of Life Sciences, Sun Yat-sen University , Guangzhou 510275, P.R. China.
authors.forename: Liang
authors.initials: L
authors.lastname: Li
authors.forename: Gang
authors.initials: G
authors.lastname: Li
authors.forename: Li-chuang
authors.initials: LC
authors.lastname: Cao
authors.forename: Guang-hui
authors.initials: GH
authors.lastname: Ren
authors.forename: Wei
authors.initials: W
authors.lastname: Kong
authors.forename: Si-di
authors.initials: SD
authors.lastname: Wang
authors.forename: Geng-shan
authors.initials: GS
authors.lastname: Guo
authors.forename: Yu-Huan
authors.initials: YH
authors.lastname: Liu
mesh_terms: D003432:Cross-Linking Reagents / Q000737:chemistry*; D004795:Enzyme Stability; D004800:Enzymes, Immobilized; D005690:Galactose / Q000378:metabolism*; D015723:Gene Library; D019015:Geologic Sediments / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D056186:Metagenomics; D009844:Oligosaccharides / Q000096:biosynthesis*; D011994:Recombinant Proteins; D001616:beta-Galactosidase / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D003432:Cross-Linking Reagents; D004800:Enzymes, Immobilized; D009844:Oligosaccharides; D011994:Recombinant Proteins; D001616:beta-Galactosidase; D005690:Galactose
keywords: cross-linked enzyme aggregates; galacto-oligosaccharides; immobilization; β-Galactosidase