Molecular Mechanisms in Yeast Carbon Metabolism: Bioethanol and Other Biofuels
Biofuels, such as ethanol, biodiesel and biogas, have the potential to replace a large proportion of transportation fuels that presently are mainly produced from fossil raw materials. Bioethanol, which is the product of the fermentative energy metabolism
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Molecular Mechanisms in Yeast Carbon Metabolism: Bioethanol and Other Biofuels Volkmar Passoth
Abstract Biofuels, such as ethanol, biodiesel and biogas, have the potential to replace a large proportion of transportation fuels that presently are mainly produced from fossil raw materials. Bioethanol, which is the product of the fermentative energy metabolism of yeasts, is currently the major biofuel on the global market. It is to a large extent generated from first-generation substrates, i.e. food grade raw materials. There are huge research efforts to develop ethanol processes based on non-food lignocellulosic materials. Using—omics technologies, metabolic and evolutionary engineering, strains of, predominantly, Saccharomyces cerevisiae have been isolated that display enhanced inhibitor and general stress tolerance, lowered glycerol production and a broadened substrate spectrum (including the fermentation of pentose sugars released from hemicellulose). Expression of these features in industrial isolates may within a relatively short time generate strains robust enough for commercial ethanol production from lignocellulose. S. cerevisiae has also been modified to produce the advanced biofuel butanol. Although yields and production rates are still below the threshold for industrial applications, tools for further developments are now available. Biodiesel production by either oleaginous yeast species that can naturally accumulate high amounts of lipids or by genetically engineered S. cerevisiae are further examples of how yeasts can be used for biofuel production. Sustainable production of biofuels requires the integration of all steps of handling biomass, including preservation, pretreatment, fermentation and conversion of side products into high value compounds. In all these steps, yeasts have great technological potential.
V. Passoth (&) Department of Microbiology, Swedish University of Agricultural Sciences, Box 7025, SE-75007 Uppsala, Sweden e-mail: [email protected]
J. Piškur and C. Compagno (eds.), Molecular Mechanisms in Yeast Carbon Metabolism, DOI: 10.1007/978-3-642-55013-3_9, Springer-Verlag Berlin Heidelberg 2014
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V. Passoth
9.1 Introduction Biofuels are reduced organic compounds, whose oxidation energy is used for heating, producing electricity and running combustion engines, mainly for transportation. The metabolic activity of photosynthetic organisms is the basis for both the origin of fossil fuels and biofuel generation, but, in contrast to fossil fuels, biofuels are generated from renewable biomass. Currently, bioethanol, biogas and biodiesel are those biofuels that are commercially used in transportation. However, the present global society primarily runs on fossil fuels; biofuels represent less than 4 % of the total global transportation energy. To move away from this largescale consumption of fossil resources requires both, measures to reduce the global energy consumption and a considerable development of sustainable energy technologies (Cheng and Timilsina 2011; Vanholme et al.
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