Nowadays, chitosan is considered as one of the most important polysaccharides due to its large number of applications, for example in food or pharmaceutical industries. The necessity to replace non-natural polymers by natural ones is the principal reason for market growing of chitosan. Moreover, this polysaccharide possesses strong biological activities, useful in the wine industry.
Chitosan is a copolymer of glucosamine and N-acetyl glucosamine connected through β-(1,4)- linkages. It is most commonly derived from chitin found in marine resources especially in shrimp cells. However, fungal sources of chitin exist (chitin-glucan) originating from cells walls of Aspergillus niger or Agaricus bisporus and it is the only form allowed in oenology. The fungal chitin presents the advantage to eliminate the need for marine resources.
For the first time, a green chemistry process using hydrogen peroxide (H2O2) has been developed for molecular weight (Mw) reduction of fungal chitosan, and to produce chitosan fractions with controlled Mw with a known acetylation and polymerisation degree. Acetylation degree can be obtained from proton NMR spectroscopy or conductimetric analysis, and degree of polymerisation and Mw by HPLC/SEC analysis. The controlled radical hydrolysis of fungal chitosan is a simple, rapid and environmentally friendly method (due to the use of small amounts of hydrogen peroxide), to produce quantities ranging from milligrams (laboratory) to kilograms (semi-industrial scale), with good yields and without altering properties of oligo- and low molecular weight chitosans, contrary to others degradation methods.