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Enhancing saccharification of cassava stems by starch hydrolysis prior to pretreatment

Martín, Carlos, Wei, Maogui, Xiong, Shaojun, Jönsson, Leif J.
Industrial crops and products 2017 v.97 pp. 21-31
Fourier transform infrared spectroscopy, X-ray diffraction, acetates, cassava, cellulose, enzymatic hydrolysis, hydrolysis, nuclear magnetic resonance spectroscopy, saccharification, starch, stems, sugars, sulfuric acid
Chemical characterization of cassava stems from different origin revealed that glucans accounted for 54–63% of the dry weight, whereas 35–67% of these glucans consisted of starch. The cassava stems were subjected to a saccharification study including starch hydrolysis, pretreatment with either sulfuric acid or 1-ethyl-3-methylimidazolium acetate ([Emim]OAc), and enzymatic hydrolysis of cellulose. Starch hydrolysis prior to pretreatment decreased sugar degradation, improved enzymatic convertibility of cellulose, and increased overall glucan conversion. Glucan recovery after pretreatment of starch-free cassava stems (SFCS) was around 85%, but below 52% when the stems were pretreated under the same conditions without preparatory starch hydrolysis. The total amount of hydrolyzed glucan after cellulose hydrolysis was two-fold higher for pretreated SFCS than for directly pretreated stems. Pretreatment with [Emim]OAc resulted in 20% higher glucan conversion than pretreatment with acid. Pyrolysis-GC/MS, X-ray diffraction, CP/MAS 13C NMR and FTIR analyses revealed major differences between H2SO4- and [Emim]OAc-pretreated material.