Recovery of Chitin from Agaricus bisporus Mushrooms: Influence of Extraction Parameters and Supercritical CO2 Treatment on Fresh Mushrooms and Production Residues

Chitin and chitosan, versatile biopolymers extensively used in the food and cosmetic industries, are traditionally sourced from crustaceans. However, fungi such as <i>Agaricus bisporus</i> mushrooms present a sustainable, non-animal alternative. This study explored the potential of different <i>Agaricus bisporus</i> samples, including fresh mushrooms and production residues, as sources of chitin. Given that <i>Agaricus bisporus</i> mushrooms are also a rich source of ergosterol, the study additionally incorporated samples treated with supercritical carbon dioxide (scCO₂). The effects of deproteinisation conditions-specifically the number of successive extractions, sodium hydroxide concentration, and extraction time-were evaluated for fresh mushroom samples in terms of alkali-insoluble matter, chitin yields, and the degree of deacetylation (<i>DD</i>), with the latter determined by Fourier-transform infrared spectroscopy. The results indicated that extraction time had no statistically significant impact on AIM or chitin yield, while the <i>DD</i> increased with prolonged extraction, plateauing after 60 min. Higher sodium hydroxide concentrations enhanced deacetylation, but adversely affected extraction yields. No significant differences in chitin's <i>DD</i> were observed between fresh mushroom and production residue samples, regardless of scCO₂ treatment. This study demonstrates the viability of recovering chitin from <i>Agaricus bisporus</i> mushroom bio-residues, including those treated with scCO₂, offering a sustainable and eco-friendly alternative for chitin production.