title: Continuous production of lactulose by immobilized thermostable beta-glycosidase from Pyrococcus furiosus.
abstract: A continuous enzymatic process for the production of the prebiotic disaccharide lactulose through transgalactosylation was developed using free and immobilized beta-glycosidase from Pyrococcus furiosus. The hyperthermostable beta-glycosidase (CelB) was immobilized onto an anion-exchange resin (Amberlite IRA-93) or onto Eupergit C with immobilization yields of 72% and 83%, respectively. The immobilized biocatalysts demonstrated specific activities of 920 nkat g(-1) dry carrier and 1500 nkat g(-1) dry carrier at 75 degrees C with p-nitrophenyl-beta-D-galactopyranoside as substrate. Continuous biotransformations in packed-bed reactors using carrier bound CelB and in an enzyme membrane reactor using free CelB were carried out at 75 degrees C. Maximum lactulose yields of 43% related to the initial lactose concentration were reached with the carrier bound CelB preparations. The corresponding productivities were 52 glactulose l(-1)h(-1) (Amberlite IRA-93) and 15 glactulose l(-1)h(-1) (Eupergit C), respectively. The free enzyme tested in an enzyme membrane reactor showed a product yield of 41% and a productivity of 12 glactulose l(-1)h(-1) in the first day. While both carrier bound CelB preparations were 100% stable for at least 14 days, the half-life of the free CelB in the enzyme membrane reactor was only about 1.5 days.
authors.affiliation: University of Hohenheim, Institute for Food Science and Biotechnology, Department of Biotechnology, Garbenstr. 25, 70599 Stuttgart, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Mayer
authors.forename: B
authors.initials: B
authors.lastname: Kranz
authors.forename: L
authors.initials: L
authors.lastname: Fischer
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D019149:Bioreactors; D001711:Biotransformation; D004795:Enzyme Stability; D004800:Enzymes, Immobilized / Q000378:metabolism*; D005632:Fructose / Q000378:metabolism; D007785:Lactose / Q000378:metabolism; D007792:Lactulose / Q000096:biosynthesis*; D008567:Membranes, Artificial; D020027:Pyrococcus furiosus / Q000201:enzymology*; D012116:Resins, Plant; D012212:Rheology; D013696:Temperature; D001617:beta-Glucosidase / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D004800:Enzymes, Immobilized; D008567:Membranes, Artificial; D012116:Resins, Plant; D005632:Fructose; D007792:Lactulose; C028629:IRA-93 resin; C406923:CelB protein, Pyrococcus furiosus; D001617:beta-Glucosidase; D007785:Lactose