Efficient extraction of chitin-glucan complex from Shiitake mushroom with deep eutectic solvent

In recent years, deep eutectic solvents (DESs) have garnered significant attention in the field of natural product extraction due to their eco-friendliness and tunable properties. In this work, six DES systems were utilized to extract chitin-glucan complex (CGC) from Shiitake mushroom (namely Lentinula edodes var. crispum) with choline chloride (ChCl) and betaine(Bet) as hydrogen bond acceptors (HBAs) and lactic acid (LA), malonic acid (MA), and urea (U) as hydrogen bond donors (HBDs). Through systematic experiments and calculations, the ChCl/LA (CLA) system exhibited the best overall performance in extracting chitin at 80 ℃, achieving a CGC yield of 32.3 %, the highest purity of chitin reached (47.5 %), a chitin acetylation degree (DA) of 65.16 %, excellent deproteinization (6.32 % residual protein) and demineralization capabilities (0.47 % residual CaCO₃). In comparation, the CGC yield of NaOH is only 21.2 %. Multiple testing analyses have confirmed that the CGC extracted by DES can maintain the composite structure of chitin and β-glucan, and has a certain degree of thermal stability, although its crystallinity is reduced and the surface is rough. Notably, the obtained CGC did not exhibit toxicity to L929 cells, with a survival rate above 80 %, which demonstrates its potential as biomaterial. This study provides a novel strategy for the green and efficient extraction of fungal chitin and its high-value utilization.