A Combined Photobiological-Photochemical Route to C10 Cycloalkane Jet Fuels from Carbon Dioxide via Isoprene

Abstract

The hemiterpene isoprene is a volatile C5 hydrocarbon with industrial applications. It is generated today from fossil resources, but can also be made in biological processes. We have utilized engineered photosynthetic cyanobacteria for direct, light-driven production of bio-isoprene from carbon dioxide, and show that isoprene in a subsequent photochemical step, using either near-UV or simulated or natural solar light, can be dimerized into limonene, paradiprene, and isomeric C10H16 hydrocarbons (monoterpenes) in high yields under photosensitized conditions (above 90% after 44 hours with near-UV and 61% with simulated solar light). The optimal sensitizer in our experiments is di(naphth-1-yl)methanone which we use with a loading of merely 0.1 mol%. It can also easily be recycled for subsequent photodimerization cycles. The isoprene dimers generated are a mixture of [2+2], [4+2] and [4+4] cycloadducts, and after hydrogenation this mixture is nearly ideal as a drop-in jet fuel. Importantly the photodimerization can be carried out at ambient conditions. However, the high content of hydrogenated [2+2] dimers in our isoprene dimer mix lowers the flash point below the threshold (38 °C), yet, these dimers can be converted thermally into [4+2] and [4+4] dimers. When hydrogenated these monoterpenoids fully satisfy the criteria for drop-in jet fuels with regard to energy density, flashpoint, kinematic viscosity, density, and freezing point. Life-cycle assessment results show a potential to produce the fuel in an environmentally sustainable way.

Mapping competitive pathways to terpenoid biosynthesis in Synechocystis sp. PCC 6803 using an antisense RNA synthetic tool

“…We therefore started by characterizing an isopreneproducing Synechocystis strain, generated in another study [22], which presents stable expression and consistent productivity, to be used as a base strain for the gene knockdown experiments. This strain over-expresses DXS from Plectranthus barbatus, native Synechocystis IDI and the isoprene synthase from Eucalyptus globulus, for higher production of isoprene [18,21,23,24], with the genes integrated in the slr0168 locus, described as a neutral site in the cyanobacterial chromosome [25] (Fig.…”

“…When Fig. 2 Schematic representation of the synthetic devices integrated in the cyanobacterial chromosome (A) for production of either isoprene (top [22]) or bisabolene (bottom), as well as the self-replicating vector containing the Hfq-MicC asRNA regulatory tool and the Hfq-asRNA complex bound to the target mRNA (B) Fig. 3 Growth (A), isoprene production per cell (B) and specific isoprene productivity (C) of the NS1::2MEP-EgIspS Synechocystis strain over the course of 24 h of cultivation in closed system combined, the Hfq-asRNA complex interferes with mRNA translation and promotes target RNA degradation [16].…”

Isoprene Telomers for Biodiesel Applications

“…Isoprene is a naturally occurring hemiterpene produced by many plants. 31,32 Recently, isoprene has also been produced in excellent yields using engineered enzymes. 33,34 The alcohols, on the other hand, are widely available chemicals in the biomass supply chain.…”