High-temperature fermentation: how can processes for ethanol production at high temperatures become superior to the traditional process using mesophilic yeast?
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The process of ethanol fermentation has a long history in the production of alcoholic drinks, but much larger scale production of ethanol is now required to enable its use as a substituent of gasoline fuels at 3%, 10%, or 85% (referred to as E3, E10, and E85, respectively). Compared with fossil fuels, the production costs are a major issue for the production of fuel ethanol. There are a number of possible approaches to delivering cost-effective fuel ethanol production from different biomass sources, but we focus in our current report on high-temperature fermentation using a newly isolated thermotolerant strain of the yeast Kluyveromyces marxianus. We demonstrate that a 5°C increase only in the fermentation temperature can greatly affect the fuel ethanol production costs. We contend that this approach may also be applicable to the other microbial fermentations systems and propose that thermotolerant mesophilic microorganisms have considerable potential for the development of future fermentation technologies.
KeywordsKluyveromyces marxianus Saccharomyces cerevisiae Fuel Ethanol Cost
We are greatly indebted to Yutaka Mitani, Sapporo Breweries Ltd. for helpful discussions. We also thank Yuko Saito, Akiko Nishida, and Yukie Misumi for their technical assistance. The studies listed in this review have been supported by grants from the Program for Promotion of Basic Research Activities for Innovative Bioscience (PROBRAIN), the New Energy and Industrial Technology Development Organization (NEDO), and the Scientific Cooperation Program between the Japan Society for the Promotion of Science (JSPS) and the National Research Council of Thailand (NRCT).
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