Abstract
BackgroundIn an effort to ensure future energy security, reduce greenhouse gas emissions and create domestic jobs, the US has invested in technologies to develop sustainable biofuels and bioproducts from renewable carbon sources such as lignocellulosic biomass. Bio-derived jet fuel is of particular interest as aviation is less amenable to electrification compared to other modes of transportation and synthetic biology provides the ability to tailor fuel properties to enhance performance. Specific energy and energy density are important properties in determining the attractiveness of potential bio-derived jet fuels. For example, increased energy content can give the industry options such as longer range, higher load or reduced takeoff weight. Energy-dense sesquiterpenes have been identified as potential next-generation jet fuels that can be renewably produced from lignocellulosic biomass.ResultsWe developed a biomass deconstruction and conversion process that enabled the production of two tricyclic sesquiterpenes, epi-isozizaene and prespatane, from the woody biomass poplar using the versatile basidiomycete Rhodosporidium toruloides. We demonstrated terpene production at both bench and bioreactor scales, with prespatane titers reaching 1173.6 mg/L when grown in poplar hydrolysate in a 2 L bioreactor. Additionally, we examined the theoretical fuel properties of prespatane and epi-isozizaene in their hydrogenated states as blending options for jet fuel, and compared them to aviation fuel, Jet A.ConclusionOur findings indicate that prespatane and epi-isozizaene in their hydrogenated states would be attractive blending options in Jet A or other lower density renewable jet fuels as they would improve viscosity and increase their energy density. Saturated epi-isozizaene and saturated prespatane have energy densities that are 16.6 and 18.8% higher than Jet A, respectively. These results highlight the potential of R. toruloides as a production host for the sustainable and scalable production of bio-derived jet fuel blends, and this is the first report of prespatane as an alternative jet fuel.
Highlights
In an effort to ensure future energy security, reduce greenhouse gas emissions and create domestic jobs, the US has invested in technologies to develop sustainable biofuels and bioproducts from renewable carbon sources such as lignocellulosic biomass
Saturated versions of prespatane and epi-isozizaene were evaluated as aviation fuel components in this study; the unsaturated values are shown for reference
We investigated the suitability of woody biomass as a feedstock in this process for production of the potential jet fuels epi-isozizaene and prespatane using R. toruloides
Summary
In an effort to ensure future energy security, reduce greenhouse gas emissions and create domestic jobs, the US has invested in technologies to develop sustainable biofuels and bioproducts from renewable carbon sources such as lignocellulosic biomass. With jet fuel accounting for 9% of the total greenhouse gas emissions from the transportation sector [11, 12], the development of renewable alternatives has become an important priority [5,6,7,8,9,10]. Due to their high cetane numbers and energy densities, a number of tricyclic sesquiterpenes have been identified as potential components of next-generation renewable jet fuels [13,14,15]. A previous study estimated that saturated terpene jet fuels, such as epi-isozizaane, could be produced from lignocellulose and used as Jet A fuel with a minimum selling price of $0.73–0.91 per liter ($2.75–3.45 per gallon), indicating that there is a real economic potential to use these molecules as an alternative jet fuel when derived from lignocellulose [22]
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