Co-solvent system of [EMIM]Ac and DMF to improve the enzymatic saccharification of pussy willow (Salix gracilistyla Miq.)

A co-solvent system consisting of 1-ethyl-3-methylimidazolium acetate ([EMIM]Ac)/N,N-dimethyl formamide (DMF) with different mass ratios was tested to improve the enzymatic saccharification of pussy willow (Salix gracilistyla Miq.). This system effectively lowered the viscosity and increased the biomass loading in the system. The water-soluble fraction obtained from the pure [EMIM]Ac remained constant or increased slightly as the amount of DMF was increased to 70%. At [EMIM]Ac/DMF ratios of 5/5 and 3/7, longer pretreatment times and higher temperatures increased the water-soluble fraction. The crystallinity of the pretreated product was increased by increasing amounts of DMF. The yield of enzymatic saccharification by means of this co-solvent system was comparable to that based on a pure [EMIM]Ac pretreatment, even though the glucose yield was slightly lower in case of DMF amount >70%. Expectedly, longer pretreatment times and higher temperatures improved the yield of enzymatic saccharification.