Biotechnologically produced chitosans with nonrandom acetylation patterns differ from conventional chitosans in properties and activities.

Sreekumar, Sruthi; Wattjes, Jasper; Niehues, Anna; Mengoni, Tamara; Mendes, Ana C; Morris, Edwin R; Goycoolea, Francisco M; Moerschbacher, Bruno M · Nat Commun · 2022

basic_science · Level V

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Abstract

Chitosans are versatile biopolymers with multiple biological activities and potential applications. They are linear copolymers of glucosamine and N-acetylglucosamine defined by their degree of polymerisation (DP), fraction of acetylation (F<sub>A</sub>), and pattern of acetylation (PA). Technical chitosans produced chemically from chitin possess defined DP and F<sub>A</sub> but random PA, while enzymatically produced natural chitosans probably have non-random PA. This natural process has not been replicated using biotechnology because chitin de-N-acetylases do not efficiently deacetylate crystalline chitin. Here, we show that such enzymes can partially N-acetylate fully deacetylated chitosan in the presence of excess acetate, yielding chitosans with F<sub>A</sub> up to 0.7 and an enzyme-dependent non-random PA. The biotech chitosans differ from technical chitosans both in terms of physicochemical and nanoscale solution properties and biological activities. As with synthetic block co-polymers, controlling the distribution of building blocks within the biopolymer chain will open a new dimension of chitosan research and exploitation.

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