Characterization of Bioethanol Production from Hexoses and Xylose by the White Rot Fungus Trametes versicolor
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Characterization of Bioethanol Production from Hexoses and Xylose by the White Rot Fungus Trametes versicolor Rasika L. Kudahettige & Marie Holmgren & Peter Imerzeel & Anita Sellstedt
Published online: 12 March 2011 # The Author(s) 2011. This article is published with open access at Springerlink.com
Abstract Bioethanol production by white rot fungus (Trametes versicolor), identified from fungal mixture in naturally decomposing wood samples, from hexoses and xylose was characterized. Results showed that T. versicolor can grow in culture, under hypoxic conditions, with various mixtures of hexoses and xylose and only xylose. Xylose was efficiently fermented to ethanol in media containing mixtures of hexoses and xylose, such as MBMC and G11XY11 media (Table 1), yielding ethanol concentrations of 20.0 and 9.02 g/l, respectively, after 354 h of hypoxic culture. Very strong correlations were found between ethanolic fermentation (alcohol dehydrogenase activity and ethanol production), sugar consumption and xylose catabolism (xylose reductase, xylitol dehydrogenase and xylulokinase activities) after 354 h in culture in MBMC medium. In a medium (G11XY11) containing a 1:1 glucose/xylose ratio, fermentation efficiency of total sugars into ethanol was 80% after 354 h. Keywords Bioethanol . Hexoses and xylose . Hypoxic conditions . Trametes versicolor . Xylose catabolism
Electronic supplementary material The online version of this article (doi:10.1007/s12155-011-9119-5) contains supplementary material, which is available to authorized users. R. L. Kudahettige (*) : M. Holmgren : A. Sellstedt Department of Plant Physiology, Umeå Plant Science Centre, Umeå University, 90187 Umeå, Sweden e-mail: [email protected] P. Imerzeel Department of Biochemistry, University of Lund, Getingevägen 60, 22241 Lund, Sweden
Introduction Energy crops and lignocellulosic residues (such as woods and agricultural residues, which contain abundant potentially fermentable carbohydrates in the form of hexose and pentose polymers) have a huge potential as alternative, renewable bio-energy sources for major impending energy crisis in the world [1]. However, economically efficient conversion of such substrates into liquid bio-fuel, ethanol, remains challenging. Inter alia, for efficient fermentation of lignocellulosic residues to ethanol, cost-effective methods for fermenting D-xylose need to be developed, since it is the second most abundant fermentable carbohydrate in these residues [2]. Biological methods for using lignocellulosic biomass in ethanolic fermentation are becoming cost-effective. However, a major problem in industrial bio-ethanolic refineries is that the most commonly used microorganism, Saccharomyces cerevisiae, can only ferment certain mono- and disaccharides (such as glucose, fructose, maltose and sucrose) efficiently into ethanol. It cannot convert pentoses, which are also major components of lignocellulosic biomass [1]. Thus, it would be more costeffective to use microorganisms that can convert both pentoses and hexose
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