Two-Stage Acidic–Alkaline Hydrothermal Pretreatment of Lignocellulose for the High Recovery of Cellulose and Hemicellulose Sugars
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The focus of this work was to develop a combined acid and alkaline hydrothermal pretreatment of lignocellulose that ensures high recovery of both hexose and pentose. Dilute sulfuric acid and lime pretreatments were employed sequentially. Process performance was optimized in terms of catalyst concentration, retention time, and temperature using response surface methodology. Medium operational conditions in the acid stage and harsh conditions in the alkaline stage were desirable with optimal performance at 0.73 wt% H2SO4, 150 °C, 6.1 min in the first stage, and 0.024 g lime/g biomass, 202 °C, 30 min in the second stage. In comparison to single-stage pretreatments with high recovery of either glucose or xylose, two-stage process showed great promises with >80 % glucose and >70 % xylose recovery. In addition, the method greatly improved ethanol fermentation with yields up to 0.145 g/g Miscanthus, due to significantly reduced formation of inhibitory by-products such as weak acids, furans, and phenols. Supplementing biomimetic acids would further increase glucose yield by up to 15 % and xylose yield by 25 %.
KeywordsTwo-stage acidic–alkaline pretreatment Miscanthus Combined acid hydrolysis Response surface methodology Lignocellulose
This research was partially funded by Illinois Council on Food and Agricultural Research (C-FAR) under Sentinel Program. We are grateful for the courtesy of Department of Crop Science for providing Miscanthus samples. We would like to express our gratitude towards Dr. Alexander Ulanov from Metabolomics Center at the University of Illinois at Urbana-Champaign for phenolic compounds analysis. Won-Heong Lee and Yong-Su Jin are affiliated with the Energy Biosciences Institute.
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