Cyanobacteria provide an interesting platform for
biotechnological applications due to their efficient photoautotrophic growth and amenability to genetic engineering. In a future biorefinery, engineered cyanobacteria may be deployed for the production of biofuels and platform chemicals from CO2 as feedstock and by harnessing solar energy. Developing such strains may involve host engineering and pathway engineering and will require toolkits such as adaptive laboratory evolution (ALE), synthetic biology, metabolic modeling and 13C-metabolic flux analysis (13C-MFA). An ideal industrial strain of cyanobacteria would need to be fast growing, naturally transformable and tolerant to high levels of temperature, light, carbon dioxide and salt. Therefore, as a first step, we have isolated a cyanobacterial strain from India that fulfils these requirements. The strain has been deposited with the Pasteur Culture collection of Cyanobacteria (PCC) as Synechococcus sp. PCC 11801. Genome sequence of PCC 11801 shows identity of ~83% with its closest neighbour S. elongatus PCC 7942. Interestingly, the new isolate can be readily adapted for improved tolerance to various abiotic stresses. In terms of synthetic biology tools, we have characterized a number of native and synthetic promoters that can be used to express heterologous pathways. We have demonstrated the production of a number of platform chemicals such as 2,3-butanediol and succinic acid in PCC 11801 by using the native promoters. In parallel, we have developed a workflow for isotopic non-stationary 13C-MFA of cyanobacteria. The isotopic 13C labelling or the mass isotopologue distribution (MID) of over 100 intermediate metabolites and their fragments has been quantified with SWATH tandem mass spectrometry. This in turn provides a high resolution flux map, which aids the model based design of strains and efficient channelling of carbon toward the product of interest. Overall, our results show that PCC 11801 is a strong candidate for photosynthetic production of fuels and chemicals at industrial level.

Additionally, I will briefly touch upon our ongoing work in other related areas that include photo- physiology of industrial strains of microalgae and bio-catalysis for chiral synthesis of compounds of pharmaceutical interest.