title: Mechanical properties of C-5 epimerized alginates.
abstract: There is an increased need for alginate materials with both enhanced and controllable mechanical properties in the fields of food, pharmaceutical and specialty applications. In the present work, well-characterized algal polymers and mannuronan were enzymatically modified using C-5 epimerases converting mannuronic acid residues to guluronic acid in the polymer chain. Composition and sequential structure of controls and epimerized alginates were analyzed by (1)H NMR spectroscopy. Mechanical properties of Ca-alginate gels were further examined giving Young's modulus, syneresis, rupture strength, and elasticity of the gels. Both mechanical strength and elasticity of hydrogels could be improved and manipulated by epimerization. In particular, alternating sequences were found to play an important role for the final mechanical properties of alginate gels, and interestingly, a pure polyalternating sample resulted in gels with extremely high syneresis and rupture strength. In conclusion, enzymatic modification was shown to be a valuable tool in modifying the mechanical properties of alginates in a highly specific manner.
authors.affiliation: Department of Biotechnology, Norwegian University of Science and Technology, Trondheim, Norway. yrr.morch@biotech.ntnu.no
authors.forename: Y A
authors.initials: YA
authors.lastname: Mørch
authors.forename: S
authors.initials: S
authors.lastname: Holtan
authors.forename: I
authors.initials: I
authors.lastname: Donati
authors.forename: B L
authors.initials: BL
authors.lastname: Strand
authors.forename: G
authors.initials: G
authors.lastname: Skjåk-Braek
mesh_terms: D000464:Alginates / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D001704:Biopolymers / Q000737:chemistry / Q000378:metabolism; D002118:Calcium / Q000737:chemistry; D002238:Carbohydrate Epimerases / Q000378:metabolism*; D006603:Hexuronic Acids / Q000138:chemical synthesis* / Q000737:chemistry*; D020100:Hydrogels / Q000138:chemical synthesis / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008422:Materials Testing
chemical_list: D000464:Alginates; D001704:Biopolymers; D006603:Hexuronic Acids; D020100:Hydrogels; C007896:guluronic acid; C008324:mannuronic acid; D002238:Carbohydrate Epimerases; C086519:mannuronan c-5-epimerase; D002118:Calcium