Effect of bipolar membrane electrobasification on chitosanase activity during chitosan hydrolysis

Chitosanase is an enzyme that hydrolyzes chitosan, a β-(1–4) glucosamine polymer, into size-specific oligomers that have pharmaceutical and biological properties. The aim of the present work was to use the bipolar membrane technology, in particular the OH− stream produced by water splitting, for inactivation of chitosanase at alkaline pH in order to terminate the enzymatic reaction producing chitosan oligomers. The objectives consisted of studying the effect of pH: (a) on the stability of chitosanase, and (b) on the catalytic activity of chitosanase during chitosan hydrolysis. The enzyme was found to be stable in the pH range of 3–8 during at least 7 h, and partially lost its activity after 1 h at pH 8. The catalytic activity of chitosanase during chitosan hydrolysis decreased after pH adjustment by electrobasification. The reaction rate decreased by 50% from pH 5.5 to 6, whereas the reaction was completely inhibited at pH > 7. The decrease of reaction rate was due to chitosan substrate insolubilization and chitosanase denaturation at alkaline pH values.