Development of An Organically Certified Growth-Medium for Cyanobacteria.

Application of N-fixing cyanobacteria to agricultural fields provides an organic N source to crops. For a cyanobacterial biofertilizer to qualify as a certifiable organic N source, the growth medium for cyanobacteria cultivation must use organically certified chemicals. This project’s goal is to develop an organically certified growth-medium for cyanobacteria cultivation. Two experiments were conducted. Objectives of the first experiment were to produce an organic medium using organically certified chemicals, to compare growth and N-fixation of cyanobacteria grown in the organic medium to the control, and to compare nutrient levels between the organic medium and the control. Three media were prepared, Allen and Arnon  (RA) (the control), Organic Allen and Arnon (OA-1), and Vanadium-free Allen and Arnon (NVA). Cyanobacteria were cultured in all three treatments using the light box method. Results show that more cyanobacterial growth occurred when cultured in RA compared to OA-1 and NVA. The Total Kjeldahl Nitrogen and Total Solids of RA were higher than OA-1 and NVA. Significance is yet to be determined. OA-1 was too acidic. Iron and phosphorus levels of OA-1 were below RA concentrations. Low phosphorus concentrations were explained by decreased dissolution of bone meal, the utilized P source, when subjected to pH increases. Objectives of the second experiment were to produce a basic organic medium, test if bone meal can supply P in a basic medium, and decrease [Ca²⁺] of the organic medium (OA-2). The P and Ca concentrations of OA-2 were compared to those of OA-1. Results suggest that bone meal in a basic organic medium will not allow RA plant-available P concentrations to be achieved. Additionally, OA-2 [Ca²⁺] was higher than OA-1 [Ca²⁺], which suggests the need for a Ca chelating agent. Currently, the final product of this research is a basic organic medium with Fe concentration 95.5% lower than measured [Fe] of RA and plant-available P concentration 35.23% lower than measured [P] of RA. Future work is discussed.