Sustainable recovery of a chitin–glucan complex–protein biocomposite from yeast biomass using biocompatible ionic liquids

Abstract Chitin–glucan complex (CGC) is typically extracted from fungal or yeast biomass using harsh alkaline treatments that not only generate high‐salt, organic‐rich effluents, but also negatively impact the structural and functional properties of the recovered copolymer, while wasting the yeast protein fraction, which is discarded. In this work, we present an innovative, environmentally friendly procedure based on the use of cholinium acetate ([Cho][OAc]), a biocompatible ionic liquid (IL), as a novel solvent to directly recover a natural CGC–protein biocomposite from Komagataella pastoris cells. The process was optimized via response surface methodology, achieving an overall recovery yield exceeding 40 wt% under mild thermal conditions (82–116 °C) and moderate biomass loadings (7.5–15 wt%), with reaction time having minimal effect. Reaction at 90 °C for 24 h, from a 11 wt% yeast biomass suspension, resulted in the recovery of a CGC–protein biocomposite comprising 64 wt% CGC and 36 wt% protein, with minimal inorganic salts contamination (0.8 wt%). This represents a novel, value‐added biomaterial, leveraging the Generally Recognized as Safe status of K. pastoris and combining the bioactive properties of both CGC and yeast‐derived proteins. The developed IL‐based method offers a sustainable, safe, and efficient alternative to traditional approaches and opens new possibilities for the valorization of yeast biomass and the use of CGC–protein biocomposites in food, cosmetic, and biomedical applications.