Authors: Malgorzata M Jaworska
Publish Date: 2012/01/20
Volume: 19, Issue: 2, Pages: 363-369
Abstract
The current paper reports on an investigation of the kinetics of chitosan deacetylation by chitin deacetylase isolated from Absidia orchidis vel coerulea The reaction rate was correlated with the concentration of GlcNHAc units of the polymer It is shown that the process follows the Michaelis–Menten mechanism Modification of the Michaelis–Menten equation by introducing the activity of the enzyme instead of its concentration was tested and found to give a better approximation to the experimental data than the original Michaelis–Menten model Parameters for both the original and the modified Michaelis–Menten equations are also proposedThis transformation can be used for enzymatic modification of chitosan to obtain polymers with a lower degree of acetylation DA the content of GlcNHAc in a polymer chain as several properties of chitosan eg bioactivity biodegradability sorption capacity are related to acetylation degree varying with variation in DA The reaction of deacetylation can be carried out chemically with concentrated NaOH solution approx 50 90–120 °C but this causes simultaneous degradation of the chitosan chain so the polymer can be degraded even to oligomers Contrary to the chemical process enzymatic deacetylation avoids polymer degradation and a polymer with the same degree of polymerisation and much smaller acetylation degree is obtainedChitin deacetylase ChD exists as intracellular enzyme eg from Mucor rouxi Absidia orchidis or as extracellular enzyme eg produced by Colletotrichum lindemuthianum Aspergillus nidulans The mode of action of these two forms of chitin deacetylase is different It was suggested that for extracellular ChD it is a “multiple chain mechanism” while for intracellular ChD it is a “multiple attack” mechanism and the deacetylation starts from nonreducing end of chitin/chitosan chain Tsigos et al 2000 Blair et al 2006
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