Microwave-assisted deep eutectic solvent extraction of chitin from crayfish shell wastes for 3D printable inks

Chitin, as one of the most abundant biopolymers in the world, has promising applications in various fields. However, critical challenges still remain in the extraction and value-added utilization of chitin in a cost-effective and environmentally-friendly manner. Herein, a time-saving, energy-efficient, and sustainable strategy consisting of microwave heating and deep eutectic solvents (DESs) treatment is demonstrated to extract the chitin from the crayfish shells. Benefitted from the release of hydrogen ion from acidic hydrogen bond donor of DESs and the formation of hydrogen bonding between DES components and protein, the minerals and protein are successfully removed using the choline chloride/lactic acid (CL) DESs. With the optimized extraction conditions, the high yield and purity of chitin is simultaneously obtained as 19.11% and 97.44%, respectively. Furthermore, the DESs can be recycled and reused for 4 times with ease, which is conductive to reducing the extraction cost and realizing the sustainable development. Finally, the extracted chitin can be further dissolved in DESs to prepare a viscoelastic ink, which displays superior rheological properties and 3D printability. This study provides a green and facile method for chitin production and opens an exciting avenue for the high value-added utilization of chitin as 3D printing ink.