A method for direct preparation of chitosan with low molecular weight from fungi.

By modifying the common method for the preparation of chitosan from fungi, low molecular weight chitosan with an average MW of 4.5 x 10(4) g/mol and a numerical MW of 1.7 x 10(4) g/mol can be directly extracted from the raw material without the need of thermal or chemical depolymerization. Based on the solubility of low molecular chitosan up to alkaline pH ranges, reprecipitation and washing with ethanol is required to keep the low molecular fraction within the preparation. The use of water for washing between the preparation steps would cause solving and discarding of the low molecular chitosan. The chitosan was analyzed by laser light scattering and 1H-NMR spectroscopy.