The development of sustainable chemical feedstock production is important for reduction of CO2 emissions and replacement of fossil fuels as raw material. Harvesting solar energy via photosynthesis is one of the nature’s remarkable achievements that could also be a solution for the future global economy. For instance first generation of bioethanol production used photosynthetically fixed carbon from crop plants. However, the impacts on the environment and the food supply raised ethical questions about these practices. Therefore, there is a growing interest in using photosynthetic microorganisms to couple CO2 capture to chemical synthesis. The ability of cyanobacteria or microalgae to fix CO2 into organic matter using solar energy qualifies them as cellular factories for production of biofuels and bio-based chemical blocks. In addition to sunlight as an energy source for carbon assimilation, cyanobacteria require only water and inorganic and trace nutrients for growth.
Compared to most microalgae, cyanobacteria are amenable to genetic manipulation, allowing the introduction of complex biosynthetic pathways into these cells by synthetic biology approaches. These efforts led to many cyanobacterial strains that produce an impressive range of products.
Isoprene (C5H8) is a volatile C5 hydrocarbon that is preferentially used as feedstock in the rubber industry. Currently, it is produced from fossil carbon sources. Isoprene is naturally synthesized by many plants, which release this volatile compound into the atmosphere. However, plants are not suitable for large-scale production of isoprene mostly due to the difficulty in collecting it. In addition to plants, heterotrophic bacteria such as Bacillus cereus, Pseudomonas aeruginosa, and Escherichia coli also naturally produce isoprene. The team of Nadin Pade of the University of Rostock in Germany generated cyanobacterium Synechocystis sp. strains expressing plant isoprene synthase (IspS) and capable of producing isoprene.
The use of cyanobacteria as single-cell factory would increase the eco-efficiency of chemical industry since it replaces the use of freshwater by saltwater-based systems. The Pade’s research group investigated the isoprene production rate in the presence of high and low NaCl concentrations. They analyzed the effects of isoprene production on cyanobacterial metabolism and the regulation of gene expression via metabolomics and transcriptomics. A new online measurement of isoprene production by single photon ionization time-of-flight mass spectrometry (SPI-MS) allowed them the use of an open-cultivation system, which resulted in higher isoprene production rates than in closed-cultivation systems. Find the open research article in Biotechnology for Biofuels.