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Adaptability of Trametes versicolor to the lignocellulosic inhibitors furfural, HMF, phenol and levulinic acid during ethanol fermentation
Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
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2016 (English)In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 90, 95-100 p.Article in journal (Refereed) Published
Abstract [en]

Ligno-cellulosic biofuels, notably ethanol produced in processes involving biological fermentation, have high potential as renewable alternatives to fossil fuels. However, ligno-cellulose pretreatment procedures generate substances that inhibit current biocatalysts. Thus, efficient methods are required for improving these organisms' tolerance or developing new biocatalysts with higher tolerance to the inhibitors. For this, greater knowledge of the mechanisms involved is needed. Therefore, we examined effects of common inhibitors (phenol, levulinic acid, HMF (hydroxymethylfurfural) and furfural) on growth, utilization of sugars (xylose, mannose and glucose) and enzyme activities of a tolerant organism, the white-rot fungus Trametes versicolor, during 15-day incubations. The fungus metabolized and grew in the presence of all the inhibitors (singly and together) at the applied concentration (0.2–0.6 g/L). When all inhibitors were added, no significant effect of sugar utilization was shown. However, levulinic acid added solely reduced xylose (but not xylose-degrading enzymes) and mannose utilization, but not glucose utilization. Physiological and biotechnological implications of the findings are discussed such as usage of Tversicolor as a detoxifying agent in ethanol production.

Place, publisher, year, edition, pages
2016. Vol. 90, 95-100 p.
Keyword [en]
Ethanol production, Enzymes, Inhibitors, Lignocellulose, Trametes versicolor
National Category
Biochemistry and Molecular Biology
Research subject
Biochemistry; Physiological Botany
Identifiers
URN: urn:nbn:se:umu:diva-119359DOI: 10.1016/j.biombioe.2016.03.030OAI: oai:DiVA.org:umu-119359DiVA: diva2:920432
Available from: 2016-04-18 Created: 2016-04-18 Last updated: 2016-09-22Bibliographically approved
In thesis
1. Trametes versicolor as biodegrader and biocatalyst when using lignocellulose for ethanol production
Open this publication in new window or tab >>Trametes versicolor as biodegrader and biocatalyst when using lignocellulose for ethanol production
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Energy consumption has increased rapidly during the last century due to population growth and greater industrialization. Lignocellulosic-based biofuels are being developed as alternatives to fossil fuels. For many years the question of how 5-carbon sugars in biomass are utilized in nature has been a vexed one. A patent by Sellstedt and Holmgren (2005) showed increased ethanol production, compared with fermentation using only Saccharomyces cerevisiae, through the use of a fungal mix from a degraded wood sample found in a forest.

The aim of the work presented in this thesis was to find a fungus that naturally utilizes 5-carbon sugars and metabolizes these sugars to ethanol; elucidate the capacity of this fungus to utilize 5-carbon and 6-carbon sugars simultaneously; assess the ability of the fungus to metabolize the inhibitors produced when lignocellulose is used; and find out whether this fungus could be used for biological pretreatment of lignocellulose to replace industrially produced enzymes.

The results showed that the fungal mix grew well on glucose, xylose, hemicellulose and cellulose. In addition, we were able to identify the fungi present, by using PCR-amplification and sequencing of DNA, as Chalara parvispora, Xylaria sp and Trametes hirsutaTrametes versicolor. In a reconstitution study, the fungi so identified were shown to produce an amount of ethanol equal to that of the fungal mix. We were also able to show that C. parvispora could produce ethanol from xylose.

T. versicolor could be grown in culture, under hypoxic conditions, with various mixtures of hexoses and xylose and with xylose alone. After 354 h of culture we found very strong correlations between ethanol fermentation (alcohol dehydrogenase activity and ethanol production), sugar consumption and xylose catabolism (xylose reductase, xylitol dehydrogenase and xylulokinase activities) in the cultures. In a medium containing a 1:1 glucose/xylose ratio, the efficiency of fermentation of total sugars into ethanol was 80 %.

A variety of inhibitors are formed during pretreatment procedures; they include, for example, phenolics, levulinic acid, HMF and furfural. These inhibitors were used in this study in order to reveal their effects on the growth of cells as well as on sugar utilization, enzyme activities and ethanol production by the white-rot fungus T. versicolor. The inhibitors had a positive effect on fresh weight, the largest increase being observed with the inhibitor furfural. T. versicolor metabolized all the inhibitors during 15 days of experimentation.

It is known that fungi can degrade cellulose, hemicellulose and lignin through a series of enzymatic reactions. Is it possible to eliminate chemical pretreatment and instead use a biological pretreatment? If T. versicolor could serve as both a biodegrader and a biocatalyst it would lead to reductions in the costs of ethanol production and lower costs for pretreatments for other renewable fuels too. Experiments with different pretreatments applied to Salix viminalis and Populus tremula were conducted with and without fungi, as well as with enzymes, to evaluate whether T. versicolor was suitable as a biodegrader. The results showed that T. versicolor was able to degrade lignocellulose to glucose, and thus is suitable as a biodegrader and in addition has xylanase and beta-glucosidase enzymes that are related to similar enzymes in other fungi.

Place, publisher, year, edition, pages
Umeå: Umeå Universitet, 2016. 52 p.
Keyword
Lignocellulose, 5-carbon, 6-carbon, Trametes versicolor, xylose reductase, xylitol dehydrogenase, xylulokinase, phenolics, levulinic acid, HMF, furfural, biodegrader, biocatalyst, pretreatment, xylanase, beta-glucosidase
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:umu:diva-125866 (URN)978-91-7601-562-9 (ISBN)
Public defence
2016-10-14, Lilla Hörsalen (KB3A9), KBC-huset, Umeå universitet, Umeå, 14:00 (English)
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Available from: 2016-09-23 Created: 2016-09-21 Last updated: 2016-09-22Bibliographically approved

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Holmgren, MarieSellstedt, Anita
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Department of Plant PhysiologyUmeå Plant Science Centre (UPSC)
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