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Liquid transport fuels from microbial yeasts - current and future perspectives
C Chuck, F Santomauro, Lisa Sargeant, Fraeya Whiffin, Tanakorn Chantasuban, Nur Rinah Abd. Ghaffar, Jonathan Wagner, R J Scott
OAI: oai:purehost.bath.ac.uk:openaire_cris_publications/91773df3-5fd8-4322-bc9c-ec02ef8d466f • DOI: https://doi.org/10.1080/17597269.2014.913905
Abstract
Global transportation is one of the major contributors to GHG emissions. It is essential, therefore, that renewable, carbon neutral fuels are developed to reduce the impact of this sector on the environment. Yeasts, especially Saccharomyces cerevisiae, are key to transforming renewable bioresources to fuels that can be used with little adaption to the current transport infrastructure. Yeasts demonstrate a large diversity that produces a great metabolic plasticity; as such, yeasts are able to produce a range of fuel-like molecules including alcohols, lipids and hydrocarbons. In this article the current and potential fuels produced through fermentation, the latest advances in metabolic engineering and the production of lipids suitable for biodiesel production are all reviewed.
Owing to growing pressure to reduce greenhouse gases and concerns over the increasing scarcity of fossil fuels, replacing liquid transport fuels with more sustainable alternatives is a key challenge of the twenty-first century [1–3]. Yeasts are capable of converting chemically functionalised and oxygenated biological compounds into a range of potential fuel molecules and could play a significant role in the production of sustainable biofuels. Yeasts are a large family of single-celled eukaryotic microorganisms of the kingdom fungi, comprising over 1300 identified species [4,5], representing perhaps as little as 1% of the total number of extant species. Yeasts have long been of interest to geneticists: in 1997, Saccharomyces cerevisiae was the first eukaryotic organism to have its genome fully sequenced [6]; and S. cerevisiae remains one of the most widely used organisms for biotechnological applications [7,8]. Whilst genomic information is available for only a small number of yeasts, there is clearly a great diversity in their physiology despite having only around 6000 genes. This is reflected in the diversity of biological niches inhabited by yeasts, which encompass the surface of fruit to the oceans [6]. This diversity is associated with great metabolic plasticity, which enable yeasts to produce a range of compounds suitable as fuels, including alcohols, triacylglycerides and more recently alternative biomolecules with the potential as drop-in fuels for the road and aviation sectors [9,10].
Central to the economic production of fuels from yeasts is a viable source of sugar feedstock. The conversion of sugars and starches is well established globally. In 2011, this equated to over 10% of the world's supply being diverted for bioethanol production [11]. However, only a fraction of the land needed to produce these feedstocks is available for fuel production and to meet demand then second generation cellulosic technologies must be developed. Typical second generation feedstocks include grasses, forestry waste, agricultural stover and food waste. It has been estimated that, globally, 5.2 billion tonnes of biomass can be available for less than $60 per tonne by 2030 [12], much of this derived from agricultural waste from the 2.3 billion tonnes of grain produced worldwide in 2011 [13]. The economic processing of the lignocellulosic feedstock is essential, and the latest advances in this area have been reviewed thoroughly elsewhere [14], including a focus on the current challenges [15, 16], the necessary pretreatment stages [17] and the inhibitors formed from the cellulosic refining process [18].
Owing to growing pressure to reduce greenhouse gases and concerns over the increasing scarcity of fossil fuels, replacing liquid transport fuels with more sustainable alternatives is a key challenge of the twenty-first century [1–3]. Yeasts are capable of converting chemically functionalised and oxygenated biological compounds into a range of potential fuel molecules and could play a significant role in the production of sustainable biofuels. Yeasts are a large family of single-celled eukaryotic microorganisms of the kingdom fungi, comprising over 1300 identified species [4,5], representing perhaps as little as 1% of the total number of extant species. Yeasts have long been of interest to geneticists: in 1997, Saccharomyces cerevisiae was the first eukaryotic organism to have its genome fully sequenced [6]; and S. cerevisiae remains one of the most widely used organisms for biotechnological applications [7,8]. Whilst genomic information is available for only a small number of yeasts, there is clearly a great diversity in their physiology despite having only around 6000 genes. This is reflected in the diversity of biological niches inhabited by yeasts, which encompass the surface of fruit to the oceans [6]. This diversity is associated with great metabolic plasticity, which enable yeasts to produce a range of compounds suitable as fuels, including alcohols, triacylglycerides and more recently alternative biomolecules with the potential as drop-in fuels for the road and aviation sectors [9,10].
Central to the economic production of fuels from yeasts is a viable source of sugar feedstock. The conversion of sugars and starches is well established globally. In 2011, this equated to over 10% of the world's supply being diverted for bioethanol production [11]. However, only a fraction of the land needed to produce these feedstocks is available for fuel production and to meet demand then second generation cellulosic technologies must be developed. Typical second generation feedstocks include grasses, forestry waste, agricultural stover and food waste. It has been estimated that, globally, 5.2 billion tonnes of biomass can be available for less than $60 per tonne by 2030 [12], much of this derived from agricultural waste from the 2.3 billion tonnes of grain produced worldwide in 2011 [13]. The economic processing of the lignocellulosic feedstock is essential, and the latest advances in this area have been reviewed thoroughly elsewhere [14], including a focus on the current challenges [15, 16], the necessary pretreatment stages [17] and the inhibitors formed from the cellulosic refining process [18].