Surface morphology and cellulose structure of Napier grass pretreated with the ionic liquid 1-ethyl-3-methylimidazolium acetate combined with either water or dimethyl sulfoxide as a co-solvent under microwave irradiation

The combination of the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate with either water or dimethyl sulfoxide (DMSO) as a co-solvent was applied for the pretreatment of Napier grass under microwave irradiation at 150 °C for 1 h in order to enhance the subsequent cellulase enzymatic hydrolysis of the cellulose to sugars via increased enzyme accessibility. The influence of the IL/water and IL/DMSO (at different IL/DMSO (v/v) ratios) pretreatment on the structural changes of the Napier grass was examined using X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analyses. The transformation of cellulose I in the IL/DMSO pretreated Napier grass was clearly observed. The results indicated that cellulose structural changes occurred and a higher yield of fermentable sugars was obtained from the subsequent enzymatic hydrolysis for the pretreated Napier grass samples with a high crystallinity index.