Abstract
The fermentation ability of thermotolerant Kluyveromyces marxianus BUNL-21 isolated in Laos was investigated. Comparison with thermotolerant K. marxianus DMKU3-1042 as one of the most thermotolerant yeasts isolated previously revealed that the strain possesses stronger ability for conversion of xylose to ethanol, resistance to 2-deoxyglucose in the case of pentose, and tolerance to various stresses including high temperature and hydrogen peroxide. K. marxianus BUNL-21 was found to have ethanol fermentation activity from xylose that is slightly lower and much higher than that of Scheffersomyces stipitis (Pichia stipitis) at 30 °C and at higher temperatures, respectively. The lower ethanol production seems to be due to large accumulation of acetic acid. The possible mechanism of acetic acid accumulation is discussed. In addition, it was found that both K. marxianus strains produced ethanol in the presence of 10 mM hydroxymethylfurfural or furfural, at a level almost equivalent to that in their absence. Therefore, K. marxianus BUNL-21 is a highly competent yeast for high-temperature ethanol fermentation with lignocellulosic biomass. Electronic supplementary materialThe online version of this article (doi:10.1186/s40064-016-1881-6) contains supplementary material, which is available to authorized users.
Highlights
Compared with Saccharomyces cerevisiae, which is widely used in ethanol fermentation industries, Kluyveromyces marxianus has advantageous potentials for application in ethanol production
Yeast strains The yeast strains used in this study were thermotolerant K. marxianus BUNL-21 (NITE P-01739) and DMKU31042 (NITE AP-283), which were isolated in Lao PDR (Results for its screening and identification will be published elsewhere.) and Thailand (Limtong et al 2007), respectively, and S. stipitis CBS 5773
In the case of Xyl as a carbon source, its assimilation and ethanol fermentation of DMKU3-1042 have been shown to be greatly reduced at high temperatures (Rodrussamee et al 2011)
Summary
Compared with Saccharomyces cerevisiae, which is widely used in ethanol fermentation industries, Kluyveromyces marxianus has advantageous potentials for application in ethanol production. One point is a relatively strong glucose repression on utilization of other sugars including xylose (Rodrussamee et al 2011). Another point is its low conversion ability of xylose to ethanol. The ethanol fermentation potential and sugar utilization profile of thermotolerant K. marxianus DMKU3-1042 have been extensively studied (Limtong et al 2007; Lertwattanasakul et al 2011; Rodrussamee et al 2011; Pimpakan et al 2012). Lignocellulose, which is a second-generation biomass for biofuels, contains glucose, xylose and arabinose
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