Fermentation of Reactive-Membrane-Extracted and Ammonium-Hydroxide-Conditioned Dilute-Acid-Pretreated Corn Stover
Acid-pretreated biomass contains various compounds (acetic acid, etc.) that are inhibitory to fermentative microorganisms. Removing or deactivating these compounds using detoxification methods such as overliming or ammonium hydroxide conditioning (AHC) improves sugar-to-ethanol yields. In this study, we treated the liquor fraction of dilute-acid-pretreated corn stover using AHC and a new reactive membrane extraction technique, both separately and in combination, and then the sugars in the treated liquors were fermented to ethanol with the glucose–xylose-fermenting bacterium, Zymomonas mobilis 8b. We performed reactive extraction with mixtures of octanol/Alamine 336 or oleyl alcohol/Alamine 336. The best ethanol yields and rates were achieved for oleyl alcohol-extracted hydrolysates followed by AHC hydrolysates, while octanol-extracted hydrolysates were unfermentable because highly toxic octanol was found in the hydrolysate. Adding olive oil significantly improved yields for octanol-extracted hydrolysate. Additional work is underway to determine if this technology is a cost-effective alternative to traditional hydrolysate conditioning processes.
KeywordsPretreatment Bioethanol Membrane Extraction Fermentation
Funding for this work was provided by the US Department of Energy’s Office of the Biomass Program. Funding for Colorado State University was provided by subcontracts with the National Renewable Energy Laboratory (KXDJ-0-30622-02, ZFT-8-88524-01). We wish to thank Ali Mohagheghi and Gary McMillen for help with the detoxification and fermentation processes.
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