Nitrogen-fixing cyanobacteria as a potential resource for efficient biodiesel production

Abstract

The incessant utilization of non-renewable energy sources persistently pollutes the earth's atmosphere and thus requires the immediate substitution by renewable energy sources such as biofuel. In this study, several nitrogen-fixing cyanobacteria are screened for biodiesel production on the basis of biomass productivity, lipid productivity, lipid profiling, and harvesting potential. The assessment performed led to the identification of Nostoc sp. MCC41, a nitrogen ficxing cyanobacteria as promising species (0.39 day−1 specific growth rate, biomass productivity of 540 mg L−1 day−1, lipid productivity of 84 mg L−1 day−1 and 15.7% lipid content). A simple filtration experiment shows that almost 81% of the biomass of Nostoc sp. MCC41 is harvested without flocculation aid, while only 23–45% of the green algae (control) could be filtered. Based on the results, further optimization of Nostoc sp. MCC41 is carried out. The optimum light intensity to attain the highest lipid productivity is found to be 54 μmol photon m−2 s−1. Continuous illumination rather than other photoperiods is superior in terms of lipid productivity. Moreover, Nostoc sp. MCC41 could grow under mixotrophic conditions revealing the potential towards an organic carbon-rich wastewater treatment. At 0.5% glucose, the Nostoc sp. MCC41 exhibited nearly five-fold increase in biomass productivity when compared to the phototrophic conditions. Lipid profiling uncovered that Nostoc sp. MCC41 has a high concentration of palmitic acid, indicating its suitability for biodiesel. Given its easy mode of harvesting, ability to grow under mixotrophic condition, and ability to fix atmospheric nitrogen, Nostoc sp. MCC41 can be considered as a potential and eco-friendly resource for efficient biodiesel production.