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

Author:
Phukoetphim, Niphaphat, Salakkam, Apilak, Laopaiboon, Pattana, Laopaiboon, Lakkana
Source:
Electronic Journal of Biotechnology 2017 v.26 pp. 84-92
ISSN:
0717-3458
Subject:
Saccharomyces cerevisiae, batch fermentation, ethanol, ethanol production, gravity, juices, nitrogen, sugars, sweet sorghum, yeast extract
Abstract:
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, 160g/L of sugar), high gravity (HG, 200 and 240g/L of sugar) and very high gravity (VHG, 280 and 320g/L of sugar) conditions by nutrient supplementation and alternative feeding regimes (batch and fed-batch systems) was investigated using a highly ethanol-tolerant strain, Saccharomyces cerevisiae NP01.In the batch fermentations without yeast extract, HG fermentation at 200g/L of sugar showed the highest ethanol concentration (PE, 90.0g/L) and ethanol productivity (QE, 1.25g/L·h). With yeast extract supplementation (9g/L), the ethanol production efficiency increased at all sugar concentrations. The highest PE (112.5g/L) and QE (1.56g/L·h) were observed with the VHG fermentation at 280g/L of sugar. In the fed-batch fermentations, two feeding regimes, i.e., stepwise and continuous feedings, were studied at sugar concentrations of 280g/L. Continuous feeding gave better results with the highest PE and QE of 112.9g/L and 2.35g/L·h, respectively, at a feeding time of 9h and feeding rate of 40gsugar/h.In the batch fermentation, nitrogen supplementation resulted in 4 to 32g/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 those in the batch fermentation.
Agid:
5627699