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Energies 2012, 5(3), 561-576; doi:10.3390/en5030561
Article

Optimization of Agitation and Aeration for Very High Gravity Ethanol Fermentation from Sweet Sorghum Juice by Saccharomyces cerevisiae Using an Orthogonal Array Design

1
,
2,3
,
4
 and
2,5,*
1 Graduate School, Khon Kaen University (KKU), Khon Kaen 40002, Thailand 2 Department of Biotechnology, Faculty of Technology, Khon Kaen University (KKU), Khon Kaen 40002, Thailand 3 Fermentation Research Center for Value Added Agricultural Products (FerVAAP), Khon Kaen University (KKU), Khon Kaen 40002, Thailand 4 Department of Plant Science and Agricultural Resources, Faculty of Agriculture, Khon Kaen University (KKU), Khon Kaen 40002, Thailand 5 Center for Alternative Energy Research and Development (AERD), Khon Kaen University (KKU), Khon Kaen 40002, Thailand
* Author to whom correspondence should be addressed.
Received: 7 December 2011 / Revised: 21 February 2012 / Accepted: 24 February 2012 / Published: 29 February 2012
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Abstract

Optimization of three parameters: agitation rate (A; 100, 200 and 300 rpm), aeration rate (B; 0.5, 1.5 and 2.5 vvm) and aeration timing (C; 2, 4 and 6 h), for ethanol production from sweet sorghum juice under very high gravity (VHG, 290 g L−1 of total sugar) conditions by Saccharomyces cerevisiae NP 01 was attempted using an L9 (34) orthogonal array design. The fermentation was carried out at 30 °C in a 2-L bioreactor and the initial yeast cell concentration was approximately 2 × 107 cells mL−1. The results showed that the optimum condition for ethanol fermentation should be A2B3C2 corresponding to agitation rate, 200 rpm; aeration rate, 2.5 vvm and aeration timing, 4 h. The verification experiments under the optimum condition clearly indicated that the aeration and agitation strategies improved ethanol production. The ethanol concentration (P), productivity (Qp) and ethanol yield (Yp/s) were 132.82 ± 1.06 g L−1, 2.55 ± 0.00 g L−1h−1 and 0.50 ± 0.00, respectively. Under the same condition without aeration (agitation rate at 200 rpm), P and Qp were only 118.02 ± 1.19 g L−1 and 2.19 ± 0.04 g L−1h−1, respectively while Yp/s was not different from that under the optimum condition.
Keywords: aeration; agitation; ethanol fermentation; orthogonal array design; Saccharomyces cerevisiae; very high gravity aeration; agitation; ethanol fermentation; orthogonal array design; Saccharomyces cerevisiae; very high gravity
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).
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Khongsay, N.; Laopaiboon, L.; Jaisil, P.; Laopaiboon, P. Optimization of Agitation and Aeration for Very High Gravity Ethanol Fermentation from Sweet Sorghum Juice by Saccharomyces cerevisiae Using an Orthogonal Array Design. Energies 2012, 5, 561-576.

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