Improvement of ethanol production from sweet sorghum juice under batch and fed-batch fermentations: Effects of sugar levels, nitrogen supplementation and feeding regimes
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Keywords

agricultural raw materials
alternative energy source
batch fermentation
bioethanol
ethanol tolerant strain
fed-batch fermentation
high gravity fermentation
normal gravity fermentation
nutrient supplementation
Saccharomyces cerevisiae
sweet sorgh

How to Cite

1.
Phukoetphim N, Salakkam A, Laopaiboon P, Laopaiboon L. Improvement of ethanol production from sweet sorghum juice under batch and fed-batch fermentations: Effects of sugar levels, nitrogen supplementation and feeding regimes. Electron. J. Biotechnol. [Internet]. 2017 Mar. 10 [cited 2024 Dec. 8];26(1). Available from: https://www.ejbiotechnology.info/index.php/ejbiotechnology/article/view/2017.01.005

Abstract

Background: Fermentation process development has been very important for efficient ethanol production. Improvement of ethanol production efficiency from sweet sorghum juice (SSJ) under normal gravity (NG, 160 g/L of sugar), high gravity (HG, 200 and 240 g/L of sugar) and very high gravity (VHG, 280 and 320 g/L of sugar) conditions by means of nutrient supplementation and alternative feeding regimes (batch and fed-batch systems) were investigated using a highly ethanol tolerant strain, Saccharomyces cerevisiae NP01.

Results: In the batch fermentations without yeast extract, the HG fermentation at 200 g/L of sugar showed the highest ethanol concentration (PE, 90.0 g/L) and ethanol productivity (QE, 1.25 g/L·h). With yeast extract supplementation (9 g/L), the ethanol production efficiency increased at all sugar concentrations. The highest PE (112.5 g/L) and QE (1.56 g/L·h) were observed with the VHG fermentation at 280 g/L of sugar. In the fed-batch fermentations, two feeding regimes, i.e. stepwise and continuous feedings, were studied at all sugar of 280 g/L. Continuous feeding gave better results with the highest PE and QE of 112.9 g/L and 2.35 g/L·h, respectively, at a feeding time of 9 h and feeding rate of 40 g sugar/h. 

Conclusions: In the batch fermentation, nitrogen supplementation resulted in 4 to 32 g/L increases in ethanol production, depending on the initial sugar level in the SSJ. Under the VHG condition, with sufficient nitrogen, the fed‑batch fermentation with continuous feeding resulted in a similar PE and increased QP by 51% compared to the batch fermentation.

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