Study of amphiphilic quaternary derivatives of chitosan: fungicide effect on Aspergillus genus species

Abstract

In the strucutre of deacetylated chitosan there are two groups susceptible to react by nucleophilic attacks: the amino groups and hydroxyl groups of the glucopyranoside rings. The hydroxyl groups may be modified by substitution of the hydrogen atoms; however their reactivities are smaller than that of the amino group. Other reactions may be also performed to selectively modify the amino groups of chitosan aiming to modify its properties. This project has as main purpose the synthesis of amphiphilic derivatives of chitosan with a fixed proportion of quaternary groups and varied hydrophobic contents attached to the chitosan main chain. These derivatives will be tested as biofungicides against the fungus Aspergillus Flavus. The project will be performed in three steps I) synthesis and characterization of the modified polysaccharides II) study of the aggregation process in aqueous solution and III) the microbiological step. Hydrophobic groups grafted to the chitosan main chain may increase the interaction with cell's membrane of the fungus. Therefore, the modification of this parameter may favor the formation of pores in the cell's membrane, increasing the antifungal activity of chitosan. The aiming of the microbiological step is to evaluate the effect of hydrophobic content of the derivatives on the antifungal activity against the fungus. (AU)