Spectroscopic/Microscopic Elucidation for Chemical Changes During Acid Pretreatment on Arundo donax

Abstract

The Arundo donax is a typical fast-growing species from the family Gramineae, which is widely cultivated in China. With a huge yield of A. donax in China, this plant offers great potential for biofuels production. The different types of organization of cell and the tissue in the A. donax could influence the efficiency of enzymatic hydrolysis. In this study, A. donax was subjected to 0.5% (w/w) sulfuric acid (H2SO4) for pretreatment at 140°C for 10 min, 20 min, 40 min, and 60 min, respectively. The changes in microstructure, chemical composition, topochemical properties were comprehensively analyzed. Using a series of spectroscopic and microscopic techniques including Fourier transform infrared spectroscopy (FT-IR), X-Ray diffraction (XRD), polarized light microscopy (PLM), and confocal Raman microscopy (CRM) to obtain the correlative structural and chemical information. Analysis results of chemical composition, FT-IR spectra and XRD indicated that with increasing reaction time, more hemicellulose and lignin would be removed. Correspondingly, there was an obvious increase of the cellulose relative crystallinity via extending reaction time. Results of the PLM observations showed that the birefringence gradually dimmed due to the diminishing of the cellulose component. Furthermore, the CRM mapping images showed the lignin component in compound middle lamellar (CML) was difficult to remove relatively as compared with that in secondary walls. These results indicated that the combination of spectroscopic and microscopic elucidation could give an insightful understanding of chemical changes in cellular level during pretreatment.

Keywords

• Arundo donax
• pretreatment
• topochemistry
• cellulose
• lignin