# Electrospinning of Chitosan for Antibacterial Applications--Current Trends
## 3 Chitin
### Chitin Resources In Several Types of Mushrooms  
As a structural component, chitin is commonly included in the skeletons of invertebrates such as insects, sponges, squid, and octopus, as well as in shellfish derived from the waste of processing marine products, such as crabs, shrimp, and krill [36]. However, chitin also exists in the structure of the mushroom cell wall and determines its shape and rigidity [36; 37]. The mushroom _Ganoderma Lucidum_ was dried for 9 days, then the dried biomass was pulverized and washed with deionized water, subjected to ultrasonic vibration for 40 min to break cell membranes and facilitate further reactions, and finally centrifuged [36]. The obtained powder was washed with ethanol for 24 h to form a polysaccharide precipitate and to obtain purer chitin. Afterward, it was repeatedly deproteinized with alkaline solution NaOH at 100 \({}^{\circ}\)C for 2 h, 3 times in total, then neutralized. The extracted crude chitin was decolorized with potassium permanganate (KMnO\({}_{4}\)) for 1 h, then treated with oxal acid (C\({}_{2}\)H\({}_{2}\)O\({}_{4}\)) for 1h leading to an increased crystallinity. In the end, the suspension was centrifuged, washed, and neutralized with water, then dried at 50 \({}^{\circ}\)C. The yield of chitin was 14.42 mg per gram of dry biomass and the examined morphology revealed typical characteristics of chitin obtained from different sources, which shows that _Ganoderma Lucidum_ can be a suitable raw material for chitin [36]. Several advantages can be attributed to the extraction of chitin from the cell walls of mushrooms. Figure 3 shows the fungal mycelium of the fungus _Pleurotus ostreatus_. First, being a vegetal source lacking animal-based derivatives, the probability to cause an allerggenic response to the human body is lowered. Second, fungi contain a low level of mineral impurities; therefore, the demineralization process is omitted and the extraction method of chitin has to undergo milder treatments, preserving its chemical structure, reducing treatment costs, and promoting a more sustainable process compared to exoskeleton sources [38]. This sustainable advantage was described in a study [39] that demonstrated acid-free isolation of chitin from a fungal substrate with minimal energy consumption based on hot water, alkaline extraction, and gentle mechanical agitation. This contrasts with the conventional method of extracting chitin from crustaceans, which always requires an acid extraction step to remove minerals. Third, the physicochemical properties of chitin are better controlled, as they usually vary between the different crustacean species and their harvesting periods [40]. This is due to the automation and synchronization of mycelia production. While crustacean shell wastes are limited by seasonal supply, mycelia can be grown all year round in a rapid, automated, and controlled process by fermentation under submerged culture in bioreactors, so that each batch produces a homogeneous quality and quantity of mushroom biomass [41; 42]. Moreover, raw chitin from mushrooms has inhibitory effects on bacterial growth compared to chitin from crab shells, which does not have this effect [43]. _Agaricus bisporus_ belongs to the most consumed mushrooms worldwide due to its simple and fast growth cycle, meaning it is a good alternative for the large-scale production of chitin [44]. In a previous experiment for chitin extraction from _Agaricus bisporus_, the highest dry weight chitin yield of 7.4% was found in the stripes, which are normally wasted during mushroom production [45]. By exploiting this resource generated from mushroom waste, an interesting opportunity can be foreseen for the production of high-purity chitin using a mild alkaline treatment with NaOH at 80 \({}^{\circ}\)C for 2 h to limit its degradation, followed by a lyophilization (freeze-drying) process.