Sustainable enzymatic extraction of high-purity chitin from button mushroom (Agaricus bisporus) off-production waste: Influence of alkaline pre-treatment on physicochemical properties

• Chitin was extracted from stalks and atypical mushrooms • A simultaneous application of protease and glucanase was used. • Extracted chitin had very high purity (98-99.36%) • Electron micrographs revealed agglomerated, microfibrillar and irregular structure • The extracted chitin samples exhibited α- allotrope characteristics. This study investigated chitin extractionfrom the stalks and atypical mushrooms, the often-produced waste in the mushroom production process, using a simultaneous application of protease and glucanase with or without an alkaline pretreatment stage. A commercial chitin, chemically extracted from A. bisporus was used as the control. The purity of extracted chitin (98.92-99.36%) was slightly lower than commercial chitin (99.80%), but with comparable physicochemical properties (p < 0.05). All enzymatically extracted chitin in this study exhibited an agglomerated, microfibrillar and irregular structure, while the control showed standalone granules with weathering and cracks on the surfaces. The XRD and FTIR spectra indicated that the extracted chitin and the control belong to the α-allotrope group. The degree of acetylation was higher in the extracted chitin (76.97-78.22%) than in the control (75.05%). The highest molecular weight obtained for the extracted chitin was 4.53 × 10 2 KDa (W0548). The study demonstrated the possibility of producing pure, high molecular weight chitin from the waste produced during the commercial production of button mushrooms, using a potentially more sustainable approach than the traditional one. This enzymatic approach reduces chemical waste, as shown by the excellent results obtained for samples without the pre-treatment stage, and improves environmental safety compared to traditional methods.