Chitosan production methods influence receptor-mediated immune responses but not target-mediated antimicrobial bioactivities

Chitosans are promising polysaccharides for the growing bioeconomy, but their numerous bioactivities depend on their structural parameters. Whereas researchers are currently unraveling the influence of the degree of polymerization and the fraction and pattern of acetylation on the properties and activities of chitosans, the role of their production method has received little attention so far. In this study, we show that polymers produced by heterogeneous deacetylation (HTDA) trigger significantly higher immune responses in plants and human cells compared to chemically N-acetylated (CNA) chitosans. This may be due to a higher abundance of acetylated stretches in combination with a more regular pattern in the HTDA samples as opposed to more uniform CNA polymers with random acetylation patterns. In contrast to the receptor-mediated immune responses, antimicrobial bioactivities, which are rather target- than receptor-mediated, were not affected by the production method. The results are of great interest for chitosan research and applications in fields such as agriculture or biomedicine, where scientists should be imperatively aware of the differences between HTDA and CNA chitosans. For instance, the eliciting activities of HTDA chitosans in plants might be preferable for crop protection, while the low immune response to CNA chitosans could be desirable for biomedical applications.