It is well known that chitosan has strong antifungal properties. Alen et al. found that chitosan has inhibitory effect on 32 kinds of fungi, such as leptospira, neurospora, and stromatomycetes, in their bacteriostatic experiments on 46 kinds of fungi. Gold chitosan high-density chitosan indicates that generally, when the concentration of chitosan reaches 100 μ When g/mL, it can show antifungal property, and the antifungal property is inversely proportional to the size of chitosan particles. The degree of polymerization of chitosan has a greater impact on its antifungal properties. If the degree of polymerization decreases, the types of fungi that chitosan can inhibit will decrease, but the degree of inhibition will increase. Kendra et al. also found that the heptamer chitosan has strong antifungal property.  

Chitosan has a good inhibitory effect on Escherichia coli, Pseudomonas fluorescens, Staphylococcus aureus, Bacillus subtilis, and can also inhibit the physiological changes of fresh food. Chitosan is natural and non-toxic. It is suitable for keeping acidic and low protein foods fresh. It can agglutinate when encountering polymers and ionic compounds. For example, for fruit preservation, the dosage is 0.1% acetic acid+0.05% - 0.1% chitosan.  

The derivatives of chitosan also have good antibacterial properties, even stronger than chitosan.