What is Chitosan?

The wastes from the shellfish processing industry around the world offer the much-needed supply to meet the demand for chitin and chitosan for industrial applications. The amount of chitin in shellfish ranges from 30-60% in oyster (Albaraoye et al., 2018; Handayani et al., 2018), 69% in crab shell waste (Albaraoye et al., 2018), 23-35% in mussel (Abdulkarim et al., 2013; Danarto and Distantina, 2016; Albaraoye et al., 2018), and 40% in prawn shells (Albaraoye et al., 2018), while scallop (Amusium sp.) shells contain 9.7% chitosan (Rokhati et al., 2017).

Illustration of the chitin molecule structure, highlighting two N-acetylglucosamine units linked by β-(1→4)-bonds, forming a repeating chain.

Chitin and its deacetylated derivative chitosan are very versatile biopolymers with excellent biocompatibility, biodegradability and intrinsic antibacterial properties (Rinaudo, 2006; Kurita, 2006). These natural polymers are employed worldwide in a broad spectrum of industrial applications, such as in biomedical engineering for wound dressing and drug delivery, water treatment as green flocculants, agriculture as plant bio-stimulants, and food packaging for active shelf-life extension (Muxika et al., 2017; Crini & Lichtfouse, 2019; Almasi et al., 2020). These applications are receiving increased economic attention, which is being increasingly satisfied by valorizing marine by-products, thus transforming processing liabilities into high-value circular resources (Yan & Chen, 2015; Arbia et al., 2021).

Conversion of a crab shell into chitosan: a depiction of the chemical structure obtained from crustacean chitin via deacetylation.