Insight into the structure-function relationships of the solubility of chitin/chitosan in natural deep eutectic solvents

Recently, the development of solution processing of chitin/chitosan in natural deep eutectic solvents (NADESs) is one of the most promising strategies for handling insoluble biopolymers. A facile and efficient approach including choline chloride-based and betaine-based NADESs, were designed as solvents for chitin/chitosan with various degree of deacetylation (DD). The maximum solubility of chitin/chitosan (10.2 g/100 g) was obtained in NADESs composed of choline chloride-lactic acid (ChLa). The relationships between the solubility, crystallinity index (CrI), and DD of the dissolved chitin/chitosan with different pH values of NADESs were discussed, and the results indicated that DD of chitin/chitosan dominated its solubility. Furthermore, mechanistic analysis showed that the hydrogen-bonding interactions contained NH center dot center dot center dot OH or OH center dot center dot center dot OH between chitin and NADESs was the possible reason for better solubility of chitin in ChLa. The NADESs-chitin processing platform in this text reveals the potential of NADESs for the environmentally-aware research and developing chitin-based industrial processes and products.

Automated summary

The use of natural deep eutectic solvents for the solution processing of chitin/chitosan has shown promising potential in dealing with insoluble biopolymers. NADESs composed of choline chloride-lactic acid demonstrated the best solubility of chitin/chitosan, with the degree of deacetylation playing a key role. Hydrogen-bonding interactions between chitin and NADESs were identified as the reason for the improved solubility of chitin in ChLa, highlighting the potential of NADESs in environmentally-friendly chitin-based industrial processes and products.