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Acid-Free Ethanol-Water Pretreatment with Low Ethanol Concentration for Robust Enzymatic Saccharification of Cellulose in Bamboo

Shi, Jinghao, Liu, Jing, Li, Meng, Huang, Liulian, Chen, Lihui, Luo, Xiaolin
BioEnergy research 2018 v.11 no.3 pp. 665-676
X-ray photoelectron spectroscopy, adsorption, bamboos, biomass, cellulose, condensates, differential scanning calorimetry, endo-1,4-beta-glucanase, enzymatic hydrolysis, ethanol, hemicellulose, lignin, saccharification, sugars, China
Lignin deposition phenomenon during the liquid-hot-water (LHW) pretreatment negatively affects substrate enzymatic digestibility (SED). To overcome this limitation of LHW, acid-free ethanol-water (EW) pretreatment with low ethanol concentration was developed. With less cellulose loss and similar hemicellulose removal, adding 10% (v/v) ethanol into water (EW10 pretreatment) resulted in a lignin removal of 5.8% higher than that of LHW pretreatment conducted at the same conditions (such as 200 °C for 40 min). Although the lignin removal did not increase significantly, differential scanning calorimetry (DSC) and X-ray photoelectron spectroscopy (XPS) characterizations indicated that LHW pretreatment-induced lignin condensation was alleviated by EW10 pretreatment, leading less lignin condensates deposited on the corresponding surface of solid substrate. Moreover, compared with lignin separated from LHW-pretreated substrate, the non-productive adsorption between EW10 pretreatment-induced lignin and cellulase was significantly weakened. As a result, the SED of EW10 pretreatment was improved to 91.7%, which was higher than LHW pretreatment by 19.5%. Due to the advantages of suppressing the deposition of lignin condensates and employing ethanol at low concentration, EW10 pretreatment shows practical significance for producing fermentable sugar from abundant non-woody biomass (bamboo) in China.