It is well known that chitosan has strong antifungal properties. In the Bacteriostatic Experiment of 46 kinds of fungi by Alen et al., it was found that chitosan had inhibitory effect on 32 kinds of fungi, such as thin bacteria, Neurospora and Setaria. Gold chitosan manufacturers said that generally, when the concentration of chitosan reaches 100 μ G / ml, and the antifungal property is inversely proportional to the size of chitosan particles. The degree of polymerization of chitosan has a great impact on its antifungal properties. When the degree of polymerization decreases, the types of fungi that chitosan can inhibit are reduced, but the degree of inhibition is strengthened. Kendra et al. Also found that chitosan of heptamer has strong antifungal property.  
Chitosan has a good inhibitory effect on Escherichia coli, Pseudomonas fluorescens, Staphylococcus aureus and Bacillus subtilis, and can also inhibit the physiological changes of fresh food. Chitosan is natural and non-toxic. It is suitable for the preservation of foods that are acidic and contain less protein. It can agglutinate in the presence of polymers and ionic complexes. For example, for the preservation of fruits, the dosage is 0.1% acetic acid + 0.05% - 0.1% chitosan. Chitosan derivatives also have good antibacterial properties, even stronger than chitosan.