A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, School of Environment, Resources and Development

Thesis (M.Sc.) - Asian Institute of Technology, 2000

The aim of this study is to determine the antifungal effect of chitosan on paper. The effect of the different concentrations of chitosan (0.1 %, 0.25%, 0.5% and 1 % chitosan solution) and of oxidized starch (0.1 %, 0.25%, 0.5% and 1 % oxidized starch solution) was compared. In the case of chitosan, the effect of different degrees of deacetylation (70, 85.5 and 90%DD) and molecular weight ( 40,500 and 1,620,000 Da) was determined on the antifungal property against the organisms Aspergillus niger and Aspergillus terreus. Both of these fungi were grown on the sheets of paper placed on potato dextrose agar plate at 25 °C. Then, the fungal growth was observed for seven days. It was observed that higher concentrations (0.025 and 0.05 g/100 cm2 of paper) of chitosan were more effective than lower concentrations (0.005 and 0.013 g/100 cm2 of paper). The growth of fungi was higher on the paper sheets which used oxidized starch and lower on the paper sheets coated with chitosan. Chitosan with higher %DD (90%DD) has more antifungal effect. The effect of molecular weights of chitosan was almost the same, both high and low molecular weights could resist the growth of fungal on paper effectively. The antifungal property of the chitosan was also determined by inoculating the fungi into the potato dextrose broth mixed with chitosan at different concentrations. The results of this experiment showed that the broth with 0.25 g/L chitosan concentration could inhibit the growth of these two fungi approximately 50% in comparison with the control.