Effects of pH on pretreatment of sugarcane bagasse using aqueous imidazolium ionic liquids

• Published in: Green chemistry : an international journal and green chemistry resource : GC Vol. 15; no. 2; pp. 431 - 438
• Main Authors: ZHANYING ZHANG, O'HARA, Ian M, DOHERTY, William O. S
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 01.01.2013
• Subjects: Biological and medical sciences; Biomass; Food industries; Fundamental and applied biological sciences. Psychology; Use and upgrading of agricultural and food by-products. Biotechnology; Sugar cane(by product); Medium effect; Nitrogen heterocycle; Bagasse; pH; Saccharification; Imidazolium compound; Pretreatment; Aqueous solution; Ionic liquid
• ISSN: 1463-9262; 1463-9270
• DOI: 10.1039/c2gc36084e

Pretreatments of sugarcane bagasse for saccharification using different acid-catalysed imidazolium IL solutions (containing 20% water) at 130 degree C for 30 min were investigated. At the same solution pH, pretreatment effectiveness in terms of glucan digestibility, delignification and xylan removal was similar for aqueous 1-butyl-3-methylimidazolium methane sulfonate (BMIMCH sub(3)SO sub(3)), 1-butyl-3-methylimidazolium methyl sulfate (BMIMCH sub(3)SO sub(4)), 1-ethyl-3-methylimidazolium chloride (EMIMCl) and 1-butyl-3-methylimidazolium chloride (BMIMCl). Decreasing solution pH of aqueous IL systems from 6.0 to 0.4 increased bagasse delignification and xylan removal, and as a result, improved glucan digestibility. The glucan digestibilities for bagasse samples pretreated by IL solutions with pH less than or equal to 0.9 were >90% after 72 h of enzymatic hydrolysis. Without pH adjustment, the effectiveness of these aqueous IL solutions (except BMIMCH sub(3)SO sub(3) because of its low natural pH of 0.9) to deconstruct the biomass was poor and the glucan digestibilities of pretreated bagasse samples were <20%. These results show that pretreatment effectiveness of aqueous imidazolium ILs can simply be estimated from solution pH rather than hydrogen bond basicity ( beta ) of the IL solution.