Supercritical water valorization of chitin in a continuous reaction system

Abstract

Chitin is an abundant biopolymer of [-1,4-poly(n-acetyl-D-glucosamine)] units, produced by crustaceans, mollusks, insects, and fungi. Nowadays, chitin is discarded in massive amounts (6–8 million tons/year) as waste from the seafood industry, being underexploited as biomass resource1. Chitin has high interest as a biocompatible and biodegradable material, but also as a source of biologically active oligosaccharides and monomers, N-acetylglucosamine (depolymerization) and glucosamine (deacetylation). These monomers constitute nitrogen-containing building blocks and open the way to biorefineries of alternative biomasses, such as sea-wastes, to obtain molecules of interest, such as furan- or amine-based monomers. Several studies have shown that chitin, like cellulose, can be dissolved and hydrolyzed in supercritical water (SCW) due to the change in its properties (water density and ionic product, among others); however, due to the high chitin crystallinity, this process occurs less easily.