Premium
Enzymatic grafting of hexyloxyphenol onto chitosan to alter surface and rheological properties
Author(s) -
Chen Tianhong,
Kumar Guneet,
Harris Michael T.,
Smith Paul J.,
Payne Gregory F.
Publication year - 2000
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/1097-0290(20001205)70:5<564::aid-bit11>3.0.co;2-w
Subject(s) - chitosan , aqueous solution , biopolymer , tyrosinase , chemistry , chemical modification , surface modification , grafting , polymer chemistry , chemical engineering , polymer , contact angle , organic chemistry , enzyme , engineering
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. © 2000 John Wiley & Sons, Inc. Biotechnol Bioeng 70: 564–573, 2000.