Is chitosan biodegradable?
Even though chitosan is much less abundant in nature than chitin, its natural occurrence suggests that there must be chitosan degraders also. In fact, chitosan degrading enzymes are surprisingly widespread among micro-organisms, possibly because chitosan, just like chitin, is a good source for both carbon and nitrogen. Partially acetylated chitosans can be depolymerized to yield chitosan oligomers by both chitinases and chitosanases, the further degradation to the monomers N-acetylglucosamine and glucosamine then requires the combined action of N-acetylglucosaminidases and glucosaminidases. Alternatively, partially acetylated chitosan polymers or oligomers can also be further de-N-acetylated by the use of chitin de-N-acetylases, potentially yielding fully deacetylated chitosans which are then further degraded to the monomer glucosamine by glucosaminidases. In the human body, only chitosans with rather high degree of acetylation can be degraded slowly by the enzyme chitotriosidase (one of the human chitinases) e.g. present in blood. The chitosan oligosaccharides thus produced may be simulating human growth factors, thus supporting scar-free wound healing.