title: A novel agarolytic β-galactosidase acts on agarooligosaccharides for complete hydrolysis of agarose into monomers.
abstract: Marine red macroalgae have emerged to be renewable biomass for the production of chemicals and biofuels, because carbohydrates that form the major component of red macroalgae can be hydrolyzed into fermentable sugars. The main carbohydrate in red algae is agarose, and it is composed of D-galactose and 3,6-anhydro-L-galactose (AHG), which are alternately bonded by β1-4 and α1-3 linkages. In this study, a novel β-galactosidase that can act on agarooligosaccharides (AOSs) to release galactose was discovered in a marine bacterium (Vibrio sp. strain EJY3); the enzyme is annotated as Vibrio sp. EJY3 agarolytic β-galactosidase (VejABG). Unlike the lacZ-encoded β-galactosidase from Escherichia coli, VejABG does not hydrolyze common substrates like lactose and can act only on the galactose moiety at the nonreducing end of AOS. The optimum pH and temperature of VejABG on an agarotriose substrate were 7 and 35°C, respectively. Its catalytic efficiency with agarotriose was also similar to that with agaropentaose or agaroheptaose. Since agarotriose lingers as the unreacted residual oligomer in the currently available saccharification system using β-agarases and acid prehydrolysis, the agarotriose-hydrolyzing capability of this novel β-galactosidase offers an enormous advantage in the saccharification of agarose or agar in red macroalgae for its use as a biomass feedstock for fermentable sugar production.
authors.affiliation: Department of Biotechnology, Korea University Graduate School, Seoul, Republic of Korea.
authors.forename: Chan Hyoung
authors.initials: CH
authors.lastname: Lee
authors.affiliation: Research Center for Biobased Chemistry, Korea Research Institute of Chemical Technology, Daejeon, Republic of Korea.
authors.forename: Hee Taek
authors.initials: HT
authors.lastname: Kim
authors.affiliation: Department of Biotechnology, Korea University Graduate School, Seoul, Republic of Korea.
authors.forename: Eun Ju
authors.initials: EJ
authors.lastname: Yun
authors.affiliation: Department of Biotechnology, Korea University Graduate School, Seoul, Republic of Korea.
authors.forename: Ah Reum
authors.initials: AR
authors.lastname: Lee
authors.affiliation: Department of Food and Nutrition, Chungnam National University, Daejeon, Republic of Korea.
authors.forename: Sa Rang
authors.initials: SR
authors.lastname: Kim
authors.affiliation: Department of Food and Nutrition, Chungnam National University, Daejeon, Republic of Korea.
authors.forename: Jae-Han
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Department of Biotechnology, Korea University Graduate School, Seoul, Republic of Korea.
authors.forename: In-Geol
authors.initials: IG
authors.lastname: Choi
authors.affiliation: Department of Biotechnology, Korea University Graduate School, Seoul, Republic of Korea khekim@korea.ac.kr.
authors.forename: Kyoung Heon
authors.identifier: http://orcid.org/0000-0003-4600-8668
authors.initials: KH
authors.lastname: Kim
mesh_terms: D000362:Agar / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D050260:Carbohydrate Metabolism; D002241:Carbohydrates / Q000737:chemistry; D003001:Cloning, Molecular; D005285:Fermentation; D005690:Galactose / Q000737:chemistry / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D009844:Oligosaccharides / Q000737:chemistry / Q000378:metabolism; D010802:Phylogeny; D000461:Rhodophyta / Q000737:chemistry; D012685:Sepharose / Q000378:metabolism*; D013379:Substrate Specificity; D013696:Temperature; D014733:Vibrio / Q000201:enzymology* / Q000235:genetics; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D002241:Carbohydrates; D009844:Oligosaccharides; D000362:Agar; D012685:Sepharose; D001616:beta-Galactosidase; D005690:Galactose