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Energies 2013, 6(2), 884-899; doi:10.3390/en6020884
Article

High Level Ethanol Production by Nitrogen and Osmoprotectant Supplementation under Very High Gravity Fermentation Conditions

1
,
2,3
,
4
 and
2,3,*
1 Graduate School, Khon Kaen University, Khon Kaen 40002, Thailand 2 Department of Biotechnology, Faculty of Technology, Khon Kaen University, Khon Kaen 40002, Thailand 3 Fermentation Research Center for Value Added Agricultural Products, Khon Kaen University, Khon Kaen 40002, Thailand 4 Department of Plant Science and Agricultural Resources, Faculty of Agriculture, Khon Kaen University, Khon Kaen 40002, Thailand
* Author to whom correspondence should be addressed.
Received: 11 December 2012 / Revised: 19 January 2013 / Accepted: 4 February 2013 / Published: 8 February 2013
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Abstract

Optimization of nutrient supplements i.e., yeast extract (1, 3 and 5 g·L−1), dried spent yeast (DSY: 4, 12 and 20 g·L−1) and osmoprotectant (glycine: 1, 3 and 5 g·L−1) to improve the efficiency of ethanol production from a synthetic medium under very high gravity (VHG) fermentation by Saccharomyces cerevisiae NP 01 was performed using a statistical method, an L9 (34) orthogonal array design. The synthetic medium contained 280 g·L−1 of sucrose as a sole carbon source. When the fermentation was carried out at 30 °C, the ethanol concentration (P), yield (Yp/s) and productivity (Qp) without supplementation were 95.3 g·L−1, 0.49 g·g−1 and 1.70 g·L−1·h−1, respectively. According to the orthogonal results, the order of influence on the P and Qp values were yeast extract > glycine > DSY, and the optimum nutrient concentrations were yeast extract, 3; DSY, 4 and glycine, 5 g·L−1, respectively. The verification experiment using these parameters found that the P, Yp/s and Qp values were 119.9 g·L−1, 0.49 g g−1 and 2.14 g·L−1·h−1, respectively. These values were not different from those of the synthetic medium supplemented with 9 g·L−1 of yeast extract, indicating that DSY could be used to replace some amount of yeast extract. When sweet sorghum juice cv. KKU40 containing 280 g·L−1 of total sugar supplemented with the three nutrients at the optimum concentrations was used as the ethanol production medium, the P value (120.0 g·L−1) was not changed, but the Qp value was increased to 2.50 g·L−1·h−1.
Keywords: bioethanol; nutrient supplements; orthogonal array design; osmoprotectant; very high gravity (VHG) fermentation; Saccharomyces cerevisiae bioethanol; nutrient supplements; orthogonal array design; osmoprotectant; very high gravity (VHG) fermentation; Saccharomyces cerevisiae
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).
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Chan-u-tit, P.; Laopaiboon, L.; Jaisil, P.; Laopaiboon, P. High Level Ethanol Production by Nitrogen and Osmoprotectant Supplementation under Very High Gravity Fermentation Conditions. Energies 2013, 6, 884-899.

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