Effect of temperature and cell density on ethanol fermentation by a thermotolerant aquatic yeast strain isolated from a hot spring environment |
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Authors: | Ryohei UENO Naoto URANO AND Shigeru KIMURA |
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Affiliation: | Department of Food Science and Technology, Tokyo University of Fisheries, Minato, Tokyo 108-8477, Japan |
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Abstract: | ABSTRACT: A thermotolerant, fermentative yeast strain named RND13 from a hot spring drainage was evaluated for its ethanol-producing ability at elevated temperatures at a high substrate concentration [15% (w/v) glucose] close to the level reflecting industrial practice. The RND13 was capable of utilizing glucose almost completely at 40°C with increasing inoculum size, producing ethanol up to 6.6% (w/v), which is comparable to levels (7.0–7.2%) at 30°C. The maximum rate of ethanol production by the RND13 was found to be 9.0 g/L per h at 40°C in an inoculum sized 5% (w/v). At 43°C, however, the RND13 could not utilize glucose to completion and showed a slight drop in the extent of produced ethanol [6.0% (w/v)]. Thus, the culture at 40°C with a 5% cell inoculum was considered to be the optimal condition for ethanol production at higher temperatures in terms of batch fermentation. In the phylogenetic analysis based on the small-subunit rDNA sequence, the strain was grouped together with both Candida glabrata and Kluyveromyces delphensis , which are relatively close to Saccharomyces cerevisiae . |
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Keywords: | aquatic yeast ethanol fermentation thermotolerant |
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