Controlling chitosan molecular weight via bio-chitosanolysis

An eco-friendly method was developed for bio-chitosanolysis in order to effect depolymerization and control the molecular weight (MW) of chitosan without changing other molecular structure. Hence biodegradation of chitosan was carried out under a variety of conditions using Aspergillus niger pectinase enzyme which is in common practice. The intrinsic viscosity and MW of chitosan were found to decrease by increasing the enzyme concentration, time of incubation and temperature up to a certain limit then leveled off except the temperature. Leveling off occurred at enzyme to chitosan ratio of 0.003 (w/w), pH 4.75 and temperature 55 degrees C for 30 min. Temperature higher than 55 degrees C deactivates the enzyme and results in marginal depolymerization of chitosan. IR spectra of chitosans having different molecular weights exhibit no obvious change in the degree of acetylation or other microstructural features. The need for chitosan with such tailored molecular weights will be emphasized in a forthcoming paper. (C) 2010 Published by Elsevier Ltd.