title: Conversion of dextran to cycloisomaltooligosaccharides using an enzyme-immobilized porous hollow-fiber membrane.
abstract: This paper describes a cycloisomaltooligosaccharide glucanotransferase (CITase)-multilayer-immobilized porous hollow-fiber membrane used as an enzyme bioreactor. Dextran, a substrate with an average molecular mass of 43000, is converted into seven- to nine-glucose-membered cycloisomaltooligosaccharides, effective as a preventive for dental caries, aided by convective transport of the substrate to the vicinity of the enzyme through the pores. Epoxy-group-containing graft chains were uniformly appended onto the surface of pores throughout a porous hollow-fiber membrane by radiation-induced graft polymerization. Subsequently, a diethylamino group was introduced, as an anion-exchange moiety, to the graft chains, which caused the chains to expand toward the interior of the pores due to mutual electrostatic repulsion. The expanding graft chain provided multilayer binding sites for CITase. Fifty-five milligrams of adsorbed CITase per gram of membrane is equivalent to the degree of multilayer binding of 5. Finally, 80% of the multilayer-adsorbed CITase was immobilized via enzymatic cross-linking with transglutaminase to prevent the leakage of enzymes. CITase, with a degree of multilayer immobilization of 4, produced the target cycloisomaltooligosaccharides at a conversion yield of 55% in weight at 310 K during permeation by the dextran solution at a space velocity defined as the permeation rate divided by membrane volume of 6 per hour.
authors.affiliation: Department of Materials Technology, Faculty of Engineering, Chiba University, 1-33 Yayoi, Inage, Chiba 263-8522, Japan.
authors.forename: Tomomi
authors.initials: T
authors.lastname: Kawai
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Kawakita
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Sugita
authors.forename: Kyoichi
authors.initials: K
authors.lastname: Saito
authors.forename: Masao
authors.initials: M
authors.lastname: Tamada
authors.forename: Takanobu
authors.initials: T
authors.lastname: Sugo
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kawamoto
mesh_terms: D019149:Bioreactors; D003911:Dextrans / Q000378:metabolism*; D004800:Enzymes, Immobilized / Q000378:metabolism*; D005964:Glucosyltransferases / Q000378:metabolism*; D008567:Membranes, Artificial; D008970:Molecular Weight; D009844:Oligosaccharides / Q000737:chemistry / Q000378:metabolism*
chemical_list: D003911:Dextrans; D004800:Enzymes, Immobilized; D008567:Membranes, Artificial; D009844:Oligosaccharides; D005964:Glucosyltransferases; C087517:cycloisomaltooligosaccharide glucanotransferase