Determining the optimal nitrogen source for large-scale cultivation of filamentous cyanobacteria

As the world’s population continues to increase and the adverse effects of anthropomorphic CO2 intensify, it is becoming increasingly important to develop biofuels and chemicals from sustainable resources. Filamentous cyanobacteria, including Anabaena sp. PCC 7120, have emerged as a promising source of renewable chemicals and biofuels due to their minimal nutrient requirements and the relative ease with which they can be genetically engineered to produce a diversity of products. This study evaluated the effects of several nitrogen sources on the growth of Anabaena sp. PCC 7120, and then performed an environmental comparative study on a theoretical large-scale production process to down-select to the best nitrogen source. Sodium nitrate and ammonium chloride yielded 65 % more growth compared to the other nitrogen sources evaluated. Ammonium chloride yielded marginal savings of US$22,318 annually, compared to sodium nitrate over a 27-year lifespan of a proposed chemical production facility utilizing filamentous cyanobacteria. Sodium nitrate had substantially greater negative impacts in every environmental category compared to ammonium chloride. For example, sodium nitrate had a ∼threefold greater negative impact in human health, ecosystem quality, and resources categories. Thus, we concluded that ammonium chloride is the preferred nitrogen source in large-scale processes involving filamentous cyanobacteria.