Harnessing Enzymatic Strategies for Chitosan Depolymerization: Mining, Mechanism, and Engineering

Abstract

Chitosan, a renewable marine polysaccharide derived from chitin, holds significant potential for conversion into high‐value chitooligosaccharides with superior bioactivity and water solubility. However, the intrinsically poor solubility and low bioavailability of native chitosan severely limit its efficient utilization, necessitating the development of effective depolymerization strategies. This review comprehensively examines enzymatic depolymerization as a sustainable and efficient alternative to conventional chemical and physical methods, offering superior specificity, mild reaction conditions, and environmental compatibility. We begin with a critical comparison of these strategies to underscore the need for the development of biocatalytic approaches. Subsequently, we explore the diversity of chitosan‐degrading enzymes across various glycosyl hydrolase families, detailing their catalytic mechanisms, cleavage specificities, and key structural domains governing substrate recognition and hydrolysis. The review further summarizes protein engineering strategies, including directed evolution, semi‐rational design, and rational design, used to enhance chitosanase activity, thermostability, and product specificity. Finally, we discuss persistent challenges, such as the lack of crystal structures for certain enzyme families and the complexity of enzyme‐substrate interactions. Future research will focus on resolving uncharacterized chitosanase structures, deepening mechanistic understanding of enzyme‐substrate interactions, and integrating artificial intelligence with synthetic biology to develop robust biocatalysts tailored for industrial applications.