И-Butanol

я-Butanol has favorable properties as a gasoline blending agent and provides a valu­able target to validate R. eutropha as a host for synthetic biology [14]. The PHB synthesis pathway in R. eutropha proceeds through 3-hydroxybutyryl-CoA, which is also an intermediate in the я-butanol synthesis pathway. Our strategy will be to divert the flux from 3-hydroxybutyryl-CoA to PHB and to redirect it to я-butanol. Recent work has demonstrated that high titers of я-butanol can be produced in E. coli by choosing heterologous genes judiciously and maximizing reducing equiv­alents available for я-butanol production [2]. Therefore, a detailed understanding of the expression of heterologous genes for я-butanol production in R. eutropha and the metabolic flux in R. eutropha PHB — mutants will be essential in achieving high titers of я-butanol.

Although я-butanol can be used directly as a gasoline replacement due to its higher energy content and lower water solubility and corrosivity relative to ethanol, it would only address short-haul ground transportation, since it could not be used to power aircraft or long-range rail and trucks. Dehydration of butanol to butylenes (C4) and oligomerization affords C8, C12 and C16 olefins with some disproportion­ation to non-oligomer C9 , C10, C11, C13, C14, and C15 olefins. These olefins can undergo double-bond isomerization, skeletal isomerization, cyclization and/or aro — matization, forming isoalkenes, cycloalkenes, and/or aromatic products. Hydrogenation of this mixture may provide hydrocarbons suitable for use as jet fuels. We will transform the я-butanol obtained from H2/CO2 cultivation of engi­neered R. eutropha to these hydrocarbon mixtures and evaluate them as replacement for jet fuel. We are currently exploring novel catalysts for the dehydration and oli­gomerization of butanol to hydrocarbon mixtures that resemble jet fuel.