In the IL pretreatment step, all ILs could dissolve SWBC. Heating with [Emim][OAc] produced a darker SWBC solution than the others (Fig. S1c). Furthermore, in the precipitation step using deionized water, [Hpy][Cl] pretreatment resulted in more swelling-regenerated biomass than the others (Fig. S1d). The regenerated biomass was recovered by centrifugation and dried using a freeze dryer (Figs S1e and S1f, respectively). The regenerated SWBCs, which were pretreated using [Emim][DEP] or [Hpy][Cl], were whiter whereas the [Emim][OAc] pretreatment produced a yellowish product. It is presumed that this occurs because some [Emim][OAc] is absorbed into the pretreated SWBC biomass.