Abstract
Conventionally, the commercial supply of chitin and chitosan relies on shellfish wastes as the extraction sources. However, the fungal sources constitute a valuable option, especially for biomedical and pharmaceutical applications, due to the batch-to-batch unsteady properties of chitin and chitosan from conventional ones. Fungal production of these glycans is not affected by seasonality enables accurate process control and, consequently, more uniform properties of the obtained product. Moreover, liquid and solid production media often are derived from wastes, thus enabling the application of circular economy criteria and improving the process economics. The present review deals with fungal chitosan production processes focusing on waste-oriented and integrated production processes. In doing so, contrary to other reviews that used a genus-specific approach for organizing the available information, the present one bases the discussion on the bioprocess typology. Finally, the main process parameters affecting chitosan production and their interactions are critically discussed.
Highlights
Chitin, a structural glycan composed of randomly distributed N‐acetyl‐D‐ glucosamine (GlcNAc) residues (Figure 1a) [1], is the second most abundant biopolymer on earth [2]
The pathway of chitin biosynthesis is organized into three groups of reactions, the first leading to the formation of GlcNAc, the second yielding its activated counterpart uridine 5’‐di‐ phospho‐N‐acetylglucosamine (UDP‐GlcNAc) through a modification of the Leloir path‐ way, and the third resulting in polymer formation using UDP‐GlcNAc as the GlcNAc do‐ nor to the growing chitin chain (Figure 2) [41]
The hope is that the research and de‐ velopment of the chitosan fungal production process can be oriented in the future only and exclusively on strains that meet the generally regarded as safe (GRAS) requirement
Summary
A structural glycan composed of randomly distributed N‐acetyl‐D‐ glucosamine (GlcNAc) residues (Figure 1a) [1], is the second most abundant biopolymer on earth (more than 100 billion tons) [2]. Chitin occurs in nature in different crystalline forms denominated α‐, β‐, and γ‐ chitin, exhibiting distinct physicochemical properties (Figure 1c) The differences among these polymorphs are due to the mode with which crystalline regions’ chains are reciprocally arranged. In the α and β forms, all the chains are arranged in an antiparallel and parallel mode, respectively, while in the γ form, there is an alternation of sets of two parallel strands with single antiparallel ones [6]. Among these allomorphs, α‐chitin is the most widespread being found in arthropods and fungi; β‐chitin generally occurs in cephalopods, while γ‐chitin is rather rare. The extraction of a value‐added product, such as chitosan, may afford a profitable solution to mushroom growers and biotechnological industries considering the vast quantities of fungal‐based wastes accumulated and the ensuing expense in waste management
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