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Fermentation 2018, 4(1), 12; https://doi.org/10.3390/fermentation4010012

Integrated Process for Extraction of Wax as a Value-Added Co-Product and Improved Ethanol Production by Converting Both Starch and Cellulosic Components in Sorghum Grains

Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Wyndmoor 19038, PA, USA
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Received: 18 January 2018 / Revised: 5 February 2018 / Accepted: 11 February 2018 / Published: 13 February 2018
(This article belongs to the Special Issue Bioconversion Processes)
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Abstract

Grain sorghum is a potential feedstock for fuel ethanol production due to its high starch content, which is equivalent to that of corn, and has been successfully used in several commercial corn ethanol plants in the United States. Some sorghum grain varieties contain significant levels of surface wax, which may interact with enzymes and make them less efficient toward starch hydrolysis. On the other hand, wax can be recovered as a valuable co-product and as such may help improve the overall process economics. Sorghum grains also contain lignocellulosic materials in the hulls, which can be converted to additional ethanol. An integrated process was developed, consisting of the following steps: 1. Extraction of wax with boiling ethanol, which is the final product of the proposed process; 2. Pretreatment of the dewaxed grains with dilute sulfuric acid; 3. Mashing and fermenting of the pretreated grains to produce ethanol. During the fermentation, commercial cellulase was also added to release fermentable sugars from the hulls, which then were converted to additional ethanol. The advantages of the developed process were illustrated with the following results: (1) Wax extracted (determined by weight loss): ~0.3 wt % of total mass. (2) Final ethanol concentration at 25 wt % solid using raw grains: 86.1 g/L. (3) Final ethanol concentration at 25 wt % solid using dewaxed grains: 106.2 g/L (23.3% improvement). (4) Final ethanol concentration at 25 wt % solid using dewaxed and acid-treated grains (1 wt % H2SO4) plus cellulase (CTec2): 117.8 g/L (36.8% improvement). View Full-Text
Keywords: sorghum grains; fermentation process; fuel ethanol; sorghum wax; value-added co-products sorghum grains; fermentation process; fuel ethanol; sorghum wax; value-added co-products
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Nghiem, N.P.; O’Connor, J.P.; Hums, M.E. Integrated Process for Extraction of Wax as a Value-Added Co-Product and Improved Ethanol Production by Converting Both Starch and Cellulosic Components in Sorghum Grains. Fermentation 2018, 4, 12.

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