Effect of some common growth modulators on the biomass productivity of Synechococcus elongatus PCC 7942: A targeted algal farming initiative

Targeted algal farming using chemical modulators is an upcoming field. With microalgal biotechnology under intense focus due to its numerous benefits and wide adaptability, this field only stands to gain from the insights. We investigated 32 different modulators at concentrations ranging from 20 - 1000 nM for biomass enhancements in Synechococcus elongatus PCC 7942. The proteinogenic amino acids were beneficial at lower (20 nM) concentrations, with similar to 8.27 - 17.64% up arrow in biomass productivity, except for methionine (similar to 2.5% up arrow). Ornithine, in contrast, was better at higher concentrations (similar to 14.05 - 17.12% up arrow at 500 - 1000 nM). alpha-oxoglutarate gave a dose-dependent response with 100 nM being the most effective (similar to 12.22% up arrow), but oxaloacetate and malate were nearly comparable. Similarly, adenosine triphosphate showed better growth at lower concentrations, in contrast with adenosine monophosphate which was better at higher ones. On the other hand, shikimate was ineffective across all concentrations. Other intermediates like glycerol, 2,3-butanediol, hydroxylamine, and myo-inositol also influenced biomass. Vitamins were found to be beneficial at low concentration (20 nM) but either inhibitory or neutral otherwise. Low concentrations (20 - 50 nM) of xenobiotics like 1,10-phenanthroline, 2,6-dichlorophenol indophenol, and sodium decanoate supported growth, possibly due to their hormetic effects. During preliminary feasibility studies, some of the modulators like lysine, calcium pantothenate, hydroxylamine, and alpha-oxoglutarate were deemed profitable with respect to large scale cultivation. Future studies on determining the mechanisms of individual modulators are underway for a deeper understanding.