Chitin and N-acetylglucosamine Metabolism in Fungi - A Complex Machinery Harnessed for the Design of Chitin-Based High Value Products

Abstract

BACKGROUND: Chitin is one of the world’s most abundant biopolymers, but in contrast to cellulose its potential has so far been fairly underrated. Compared to cellulose, chitin features an additional amino-group on the hexose sugar ring that renders it a promising substrate for functional biopolymers in biomedical applications as well as biochemical synthesis of specialty and fine chemicals. Fungi with specialized life styles, such as mycoparasites and entomopathogenic fungi, have evolved an effective machinery to utilize chitin derived from other fungi and arthropods, respectively. OBJECTIVE: Fungal chitin degradation and chitin synthesis have been subject to extensive investigation in the past years to gain insight into these intricately regulated processes, which render fungi capable of harnessing the recalcitrant chitin polymer as nutritional source and building block for growth. For the development of methods to exploit chitin from these origins, the design of new products and their sustainable production through enzymatic action, identifying the regulators of the chitin anabolic and catabolic pathways will be essential. In this review our current knowledge on chitin metabolism in fungi is presented; new sources for chitin production and new products derived from enzymatic processing will be introduced. Keywords: Chitin, chitosan, N-acetylglucosamine, biopolymer, filamentous fungi, regulation, transcription factor, bio-based chemicals.