US EPA

4307102 

Journal Article 

Terpene Hydrocarbons Production in Cyanobacteria 

Melis, A 

2017 

187-198 

WOS:000388010300010 

A description is given on the development and state of the art of technologies for the renewable generation of terpene hydrocarbons to serve as renewable fuel for transportation, and chemicals for the synthetic chemistry industry, with cyanobacteria as the primary photocatalyst and isoprene (C5H8) and monoterpene (C10H16) hydrocarbons as the paradigm outputs. This approach integrates pivotal aspects of the photosynthetic biofuels concept:



a efficient sunlight utilization by cyanobacterial mass cultures;



b effective delivery and assimilation of quantities of CO2 to fast-growing cyanobacteria;



c paradigm of synthesis, spontaneous product separation from the biomass, and isoprene and -phellandrene (monoterpene) sequestration and harvesting;



d application of novel low-cost photobioreactors for the successful and cost-effective implementation of (a) through (c); and



e evaluation of isoprene (C5H8) and monoterpene (C10H16) hydrocarbons as fuel molecules, compared to alkanes and alcohols.



The effort advocates the development and application of designer cyanobacterial strains, which can grow in mass culture under bright sunlight conditions and demonstrate efficient sunlight conversion and utilization. Metabolic engineering approaches endow and enhance the yield of isoprene and monoterpene hydrocarbons generated in photosynthesis, relative to the biomass accumulated. Gaseous/aqueous two-phase photobioreactors are used for efficient conversion of sunlight and CO2 into isoprene or monoterpenes, molecules that are potential biofuels and highly valuable industrial chemicals. Following isoprene or monoterpene sequestration, the residual cyanobacterial biomass is used as feedstock of bacterial fermentations to generate biogas (a mixture of CH4 and CO2), with the residual biomass serving as bio-fertilizer. In terms of Energy Density, terpene hydrocarbons are favourably compared to alkanes, and are substantially better than similar size alcohols. The promise of a cyanobacterial 'Photosynthesis-to-Fuels' approach is the ability to transform the primary products of photosynthesis directly, in a single cyanobacterial cell, into commodity products for human industrial and domestic consumption.