Ionic Liquid-Mediated Biopolymer Extraction from Coffee Fruit

Ionic liquids (ILs) are effective solvents for biomass. Refined cellulose is commonly used; however, recent interest has grown to consider woody and herbaceous biomass and industrial crop residues like fruit peels. Here, the authors report results on the dissolution and shaping of cotton and coffee fruit (cascara) in 1,8-diazabicyclo[5.4.0]undec-7-inium acetate ([DBUH][OAc]). Cascara is a high-volume, low-value crop residue that poses an environmental and economic burden in producer countries leading to a high-value proposition if recoverable. Fruit/ionic liquid solutions (0–15% w/w dissolved at 60 °C) were characterized with respect to biomass concentration and shaped into fibers and films coagulated in DI water and methanol. Rheology was assessed using parallel plate rheometry. Cotton/IL mixtures formed better fibers compared to cascara-based solutions, which required 2.6× more biomass in solution for viable fiber formation. At 10% loading, fibers could be produced from untreated coffee fruit with diameters ranging from 18–100 microns. Coffee fruit residues and their precipitated films show that both cellulose and lignin dissolve in pure [DBUH][OAc]. Chemical characterization of cascara and cascara films demonstrates the conveyance of high concentrations of lignin and extracts that result in weaker mechanical properties. Further purification of cascara is required for effective use in structural applications.