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 CO 2 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.