摘要：A two-stage, chemical and enzymatic process can be used to prepare chitosans with
desired degrees of deacetylation. However, it is not possible to obtain products with a higher
degree of deacetylation than 84% from chitosan with an initial degree of deacetylation of 68%
when a 1.2% solution is used as a substrate for the pre-purified deacetylase from Mucor rouxii
mycelium. The objective of this study was to investigate the reasons behind this phenomenon.
The incomplete deacetylation of chitosan under the applied conditions of enzymatic reactions
was not the result of the thermal denaturation of deacetylase during the relatively long enzymatic
reaction. The amount of acetic acid released and the degree of deacetylation did not
increase as a result of adding a fresh portion of the enzyme to the reaction mixture after 10, 16,
and 24 h of the reaction. It was shown that enzymatic deacetylation could be partially inhibited
by acetic acid released during deacetylation. The main product of deacetylation . chitosans
deacetylated to about 82-84%, also decreases the rate of deacetylation. Only 35% of the total
possible acetic acid released from chitosan with a degree of deacetylation of 82% was detected
after 24 h of enzymatic deacetylation. The total inhibitory effect of both products of deacetylation
on chitin deacetylase activity was investigated by conducting enzymatic deacetylation of
chitosan with a degree of deacetylation of 82% in the presence of added acetic acid at a
concentration of 12 mmoles/ml of the reaction mixture. After 24 h, the amount of acetic acid
formed was so low that the degree of deacetylation of the product was almost unchanged.
