Current trends in fungal biosynthesis of chitin and chitosan

Abstract

Background: Chitin and chitosan are natural biopolymers found in shell of crustaceans, exoskeletons of insects and mollusks, as well as in the cell walls of fungi. These biopolymers have versatile applications in various fields such as biomedical, food industry, and agriculture. These applications are back to their biocompatibility, biodegradability, strong antibacterial effect, and non-toxicity. Outcomes: The fungal biopolymers have many features that made them more advantageous than those biopolymers from seafood waste origin. Chitin and chitosan are not components of cell wall in all fungal species. The fungal classes of Basidiomycetes, Ascomycetes, Zygomycetes, and Deuteromycetes are known to contain chitin and chitosan in their cell walls. The amounts and characters of fungal biopolymers are affected by many factors so they should be optimized before increasing the scale of production. The statistical design of experiments is the most recent and advanced approach for optimization of various factors with more reliable results. Conclusion: Although extensively studied, further studies concerning fungal chitin and chitosan should be conducted in order to be sure of safety for human use.

Chitinous polymers: extraction from fungal sources, characterization and processing towards value‐added applications

“…Chitin and chitosan aggregate into microfibrils that are connected by hydrogen bonds, conferring rigidity to the cell walls . The forms α , β and γ are the three polymorphic forms for chitin arrangements of the chains in the microfibrils.…”

“…The content of chitin/chitosan in the cell‐walls is specific to species, age and environmental conditions. It ranges between 2 and 42% on a dry basis in fungi as well as yeasts …”

“…The content of chitin and chitosan in fungal species, their structure and degree of polymerization are dependent on the species, media composition (carbon and nitrogen sources and their concentrations, micronutrients), cultivation conditions (pH, temperature, dissolved oxygen concentration) and fermentation systems (solid state or submerged, batch, fed‐batch or continuous processes) . Fungal cells are chemoorganotrophic organisms and in order to grow they need organic carbon sources.…”

“…Many reports conclude that solid state fermentation is more efficient than submerged fermentation in fungal biomass production . However, solid state fermentation presents diverse difficulties related to standardization, characterization and optimization.…”

“…The most commonly used methods for fungal cell‐wall fractionation start with a hot (40–121 °C) alkaline treatment (e.g. with NaOH 0.5–1.0 mol L –1 ) that not only disrupts the cell but also solubilizes many of its components, namely proteins, alkali‐soluble glucans and mannans . Stronger alkaline conditions (e.g.…”