Acetic acid-catalyzed hydrothermal pretreatment of corn stover for the production of bioethanol at high-solids content
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Corn stover (CS) was hydrothermally pretreated using CH3COOH (0.3 %, v/v), and subsequently its ability to be utilized for conversion to ethanol at high-solids content was investigated. Pretreatment conditions were optimized employing a response surface methodology (RSM) with temperature and duration as independent variables. Pretreated CS underwent a liquefaction/saccharification step at a custom designed free-fall mixer at 50 °C for either 12 or 24 h using an enzyme loading of 9 mg/g dry matter (DM) at 24 % (w/w) DM. Simultaneous enzymatic saccharification and fermentation (SSF) of liquefacted corn stover resulted in high ethanol concentration (up to 36.8 g/L), with liquefaction duration having a negligible effect. The threshold of ethanol concentration of 4 % (w/w), which is required to reduce the cost of ethanol distillation, was surpassed by the addition of extra enzymes at the start up of SSF achieving this way ethanol titer of 41.5 g/L.
KeywordsCorn stover Pretreatment Ethanol fermentation Enzymatic liquefaction Response surface methodology
The financial support of General Secretariat of Research and Technology (GSRT) of Greece-ESPA 2007–2013 (SYNERGASIA 2011; 11SYN_7_1579) is gratefully acknowledged. We are also grateful to Novozymes A/S for the generous gifts of Celluclast® 1.5 L, Novozyme® 188 and Cellic® CTec2, and to Lesaffre for the generous gift of Ethanol Red®.
Compliance with ethical standards
Conflict of interest
The authors declare that no conflict of interest exists.
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