Enzymatic Degradation Behaviour of Starch Conjugated Phosphorylated Chitosan

Phosphorylated chitosan (P-chitosan) was synthesized by means of graft copolymerization technique. The conjugate membranes were prepared from oxidised starch and Pchitosan using reductive alkylation crosslinking. The synthesized membranes were characterised by FT-IR. In order to characterize degradation behaviour of this conjugated system, the membranes were incubated in enzyme solutions of alpha-amylase and lysozyme as well as a physiological saline solution (PBS) used as control solution. In PBS, low starch containing membranes (0.16-0.38 weight (starch)/weight (P-chitosan), (ws/wc)) and control membranes have not showed significant change in their weight during two months of incubation. High starch containing membranes (0.73-1.04 ws/wc) indicated less than 20 % weight loss after this period. After α-amylase incubation, a distinct degradation behaviour was observed from starch-P-chitosan membranes. The degradation of the conjugate membranes was found to be fast with increasing starch content. Weight losses between 20 to 55 % were detected for the lowest (0.16 ws/wc) starch and highest (1.04 ws/wc) starch containing membranes, respectively. In the lysozyme degradation study, the conjugate membranes were not degraded by enzymatic activity and the weights of membranes were seen to be increased about 20 % because of swelling. The control membranes showed gradual weight loss in enzyme solutions. These results indicated the lysozyme degradation of starch-free P-chitosan membranes and inhibition of degradation P-chitosan by highly conjugated starch molecules.