Chitin in fungi

A number of important papers could not be cited in this chapter, due to the length limitations and the specific target of the chapter. For example, the antimicrobial activity of chitosans [349], the chitinolytic enzymes, the preparation of cosmetics, and the occurrence of chitin in fungi [350] are some of the subjects not dealt with specifically here, notwithstanding their importance. 

A-Acetyl-D-glucosamine is the precursor of chitin in fungi and animals. This sugar is also found in the cell walls of bacteria (Luckner, 1990). 

It may be that this fact was associated with the rather complex composition of fungal mycelium, consisting of chitin enclosed in a glucan matrix (Bowman, Free, 2006). Therefore, mature saprophyte mycelium are completely covered by difficult-soluble glucans and the fraction of chitin in the apical cell wall is not sufficient. As such, we supposed that these cationic isoforms bound with another major component of the fungi... 

Thus chitin is abunckmt in the sea, in diatom blooms and in the zooplankton, most notably in the shoals of krill and on the land, in invertebrates and in fungi in the soil. Potential industrial sources are wastes from shrimps and crabs, krill, squid, clams and oysters, and fungal fermentations (13). The krUl fishery alone produces 3000 tons per year, currently going to waste. 

Chitin is a polysaccharide constituted of N -acctylglucosamine, which forms a hard, semitransparent biomaterial found throughout the natural world. Chitin is the main component of the exoskeletons of crabs, lobsters and shrimps. Chitin is also found also in insects (e.g. ants, beetles and butterflies), and cephalopods (e.g. squids and octopuses) and even in fungi. Nevertheless, the industrial source of chitin is mainly crustaceans. 

Polyoxlns. The polyoxin antibiotics are effective against fungi that contain chitin in their cell walls. The resistance to polyoxlns in some fungi of this type appears to be related to a permeability factor rather than to a change in the site of action (14). Polyoxlns competitively inhibit chitin synthetase and thus prevent the incorporation of uridinediphospho-N-acetylglucosamine into the chitin polymer (14). 

Hadwiger, L.A., Kendra, D.F., Fristensky, B.W., and Wagoner, W. 1985. Chitosan both activates genes in plants and inhibits RNA synthesis in fungi. In Chitin in Nature and Technology (R.A.A. Muzzarelli, C. Jeuniaux, and G.W. Gooday, eds), pp. 209-222. Plenum Press, New York. 

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