Chitin–Glucan Complex from Pleurotus ostreatus Mushroom: Physicochemical Characterization and Comparison of Extraction Methods

Abstract

Chitin–glucan complex, an essential organic ingredient in the inner layer of the fungal cell wall, was isolated from the stalk and cap of Pleurotus ostreatus mushroom using two methods. In the first, powder of water-insoluble part was treated with NaOH in 3 successive baths, whereas in the second method an additional step was performed using acetic acid for the effective removal of soluble proteins, free chitosan and minerals. The influence of the deproteinization process on the yield and purity of the chitin-glucan complex was assessed by variation of NaOH concentration, reaction time and number of baths.The biopolymer recovered by the first method (yield from stalk 49% of dry weight, Cri 63.19%) presented residual proteins, lipids and minerals (5.52%) whereas the purest copolymer (yield\xa041.1% and minerals 3.22% of dry weight, Cri 58.43%) was produced using the second method from the stalk; the latter was mostly considered as a valuable waste from an available bio-resource that can easily be cultivated. X-ray diffraction (XRD), thermal analyses, scanning electron microscope, energy-dispersive X-ray spectroscopy, infrared spectroscopy, Kjeldahl method and Biuret test were employed to prove purity and study the physicochemical properties. Furthermore, the isolated chitin–glucan complex was compared with the chitin extracted from Agaricus bisporus mushroom. Fungal chitin could constitute a viable alternative to commercial chitin with better performance in adsorption applications, and in this respect, the results revealed that the isolation of chitinous polysaccharide from P. ostreatus (41.1%) was higher than from most cultivated mushrooms (7–36.72%).