Chitin deacetylase: from molecular structure to practical applications

Chitosan and chitooligosaccharides (COS), as derivatives of chitin through deacetylation reaction, have broad applications due to their good biodegradability, biocompatibility, and solubility. In addition, chitosan and COS are involved in cell wall morphogenesis and host–pathogen interactions in vivo. Chitin deacetylases (CDAs) are enzymes that can catalyze the de-N-acetylation of chitin. They are widely distributed in protozoa, algae, bacteria, fungi, and insects with important physiological functions. Compared with the traditional chemical method, enzymatic catalysis by CDAs provides an enzymatic catalysis method to produce chitosan and COS with controllable deacetylation site and environmental friendliness. These characteristics attract researchers to produce CDAs by fungicides or pesticides. However, researches on heterologous expression and directed evolution of CDAs are still lacking. In this review, we summarize the latest knowledge of CDAs, especially for heterologous expression systems and directed evolution strategies, which may contribute to the industrial production and future application of CDAs.