Enzymatic grafting of hexyloxyphenol onto chitosan to alter surface and rheological properties.

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TitleEnzymatic grafting of hexyloxyphenol onto chitosan to alter surface and rheological properties.
Publication TypeJournal Article
Year of Publication2000
AuthorsChen, T, Kumar, G, Harris, MT, Smith, PJ, Payne, GF
JournalBiotechnol Bioeng
Volume70
Issue5
Pagination564-73
Date Published2000 Dec 5
ISSN0006-3592
KeywordsChitin, Chitosan, Monophenol Monooxygenase, Oxidation-Reduction, Phenols, Phenyl Ethers, Rheology, Surface Properties
Abstract

An enzymatic method to graft hexyloxyphenol onto the biopolymer chitosan was studied. The method employs tyrosinase to convert the phenol into a reactive o-quinone, which undergoes subsequent nonenzymatic reaction with chitosan. Reactions were conducted under heterogeneous conditions using chitosan films and also under homogeneous conditions using aqueous methanolic mixtures capable of dissolving both hexyloxyphenol and chitosan. Tyrosinase was shown to catalyze the oxidation of hexyloxyphenol in such aqueous methanolic solutions. Chemical evidence for covalent grafting onto chitosan was provided by three independent spectroscopic approaches. Specifically, enzymatic modification resulted in (1) the appearance of broad absorbance in the 350-nm region of the UV/vis spectra for chitosan films; (2) changes in the NH bending and stretching regions of chitosan's IR spectra; and (3) a base-soluble material with (1)H-NMR signals characteristic of both chitosan and the alkyl groups of hexyloxyphenol. Hexyloxyphenol modification resulted in dramatic changes in chitosan's functional properties. On the basis of contact angle measurements, heterogeneous modification of a chitosan film yielded a hydrophobic surface. Homogeneously modified chitosan offered rheological properties characteristic of associating water-soluble polymers.

Alternate JournalBiotechnol. Bioeng.
PubMed ID11042553