Efficient conversion of xylose to ethanol by stress-tolerant Kluyveromyces marxianus BUNL-21

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.

Potential of Thermotolerant Ethanologenic Yeasts Isolated from ASEAN Countries and Their Application in High- Temperature Fermentation

“…K. marxianus DBKKUY-103, that was recently isolated, achieved the maximum ethanol concentration of 83.5 g/L, corresponding to 96.6% of the theoretical yield [47]. Nitiyon et al [37] reported that K. marxianus BUNL-21 is a highly competent yeast for high-temperature ethanol fermentation with lignocellulosic biomass. When compared with the strain DMKU 3-1042, the strain BUNL-21 had stronger ability for conversion of xylose to ethanol and tolerance to various stresses including high temperature and hydrogen peroxide.…”

“…Ethanol production at high temperatures by thermotolerant yeasts has earned much interest due to several advantages as described above [38]. There are several ethanologenic yeasts that have been characterized and classified as thermotolerant yeasts such as K. marxianus [31,37,47], P. kudriavzevii (formally known as I. orientalis) [20,48,49,65,66], Hansenula polymorpha [67], and some strains of S. cerevisiae [21,52,[68][69][70]. However, for cost-effective and efficient ethanol production, not only thermotolerance but also a broad spectrum in sugar assimilation and fermentation capability is beneficial for the conversion of a variety of raw materials containing various sugars to ethanol, especially xylose, which is the most common pentose sugar and the second most abundant after glucose in lignocellulosic biomass and algal biomass [71,72].…”

“…Pachysolen tannophilus [76], H. polymorpha [67], and K. marxianus [32,37]). Among these xylosefermenting yeasts, it seems that K. marxianus has the potential for practical application in high-temperature ethanol fermentation because of its thermotolerance and ability to utilize a variety of sugars.…”

“…However, it is possible that unidentified and more beneficial thermotolerant yeasts exist in ASEAN countries, especially, thermotolerant high xylose-utilizing and ethanol-producing yeasts, which are needed for 2nd generation biomass utilization. None of the isolated K. marxianus strains, however, are able to more efficiently convert xylose to ethanol than strains of other xylose-utilizing yeasts, such as Pichia stipitis (Scheffersomyces stipitis) [32,37].…”

Evaluation of Non-Saccharomyces Cerevisiae Strains Isolated from Sea Water Against Inhibitory Compounds for Ethanol Production

“…This finding confirmed that the strains could not utilize xylose. According to Moysés et al (2016) and Nitiyon et al (2016), the present of high concentration of xylose in the medium causes the osmotic stress for yeast strain.…”