Chitosanolysis by a pectinase isozyme of Aspergillus niger—A non-specific activity

An isozyme of Aspergillus niger pectinase could depolymerize chitosan and its derivatives. The isozyme showed optimum depolymerization at pH 3.0 and 47 °C and exhibited classical Michaelis–Menten kinetics with a Km and a Vmax of 3.12 mg ml−1 and 153.85 nmol min−1 mg−1, respectively, towards chitosan, which were higher than those for chitosan derivatives. The low molecular weight chitosans (LMWC) obtained were in the range of 6–20 kDa depending on the reaction conditions. Identification of glucosamine (GlcN) and N-acetylglucosamine (GlcNAc) oligomers as depolymerized products indicated that the isozyme cleaved both GlcN-GlcN and GlcNAc-GlcN linkages. This study suggests the possible use of pectinase isozyme in place of chitosanase, which is expensive and unavailable in bulk quantity for the production of LMWC and chitooligomers.