Krysteva M.Naidenova E.Andreeva A.Huyen N.D.2024-07-102024-07-102024-07-102024-07-101995-01-011310-281810.1080/13102818.1995.10818825SCOPUS_ID:13844321386https://rlib.uctm.edu/handle/123456789/97A modification of amino groups of chitosan were performed in two directions: treatment of vicinal amino and hydroxyl groups by periodate and subsequent interaction with urea and formaldehyde in order of covalent immobilization of enzymes; alkylation of chitosan amino groups for increasing the positive charge and utilization of polymer as an anion exchanger. The binding of enzymes: lipase, trypsin, penicillin amidase and glucose oxidase to the activated matrix was done at pH 4.0, 5.0 and 3.5 respectively. The immobilization of lipase was performed at pH 4.0 and 8.0. The immobilized enzymes were characterized by their pH optimum and relative enzyme activity. The alkylation of the amino groups has been achieved by varying the modifying agent (formaldehyde in the presence of formic acid) to the chitosan. The ion-exchange properties of the ionite obtained was verified by means of ovomucoid, a protein with improved acidic characteristics. © 1995 Taylor & Francis Group, LLC.enArticle