Microalgae as a new source of chitosans

Abstract

Chitosans are a family of linear polysaccharides generally obtained from the chemical deacetylation of chitin derived from crustacean shells that have been reported to have a wide range of bioactivities. However, the development of products taking advantage of these bioactivities has lagged behind expectations. The historic main reason is the poor reproducibility of the biological effects of chitosans due to a harsh chemical deacetylation process that impairs the structure of the polysaccharides inducing variability. Another reason is the immunologic responses that these polymers may produce in the presence of traces of crustacean proteins. It is therefore necessary to gather chitosans from other non-animal sources using a more environmentally friendly and reproducible process. Publications have commented that some microalgae species might contain chitin and even chitosan in their cell walls. Hence, in order to confirm these hypotheses, a screening method has been developed to detect each of these polymers specifically amongst the wide diversity of microalgae species of Greenaltech’s library. Thanks to this screening method, natural chitins and chitosans have been found in several genera. The methodology has been validated with the extraction and physicochemical characterization of chitins and chitosans from Chlorella, something that, to our knowledge, had never been done before. At the same time, the enzymatic deacetylation process behind the natural production of chitosan in Chlorella has been studied emphasizing the identification of active chitin deacetylases. Finally, as part of an exploratory biofunctional study of microalgal chitosans, the antimicrobial, wound healing and nanocapsule-forming properties have been analyzed.