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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.