Organic culture of Spirulina: effects of C and N sources on biomass and biomolecules production in linear and helical morphotypes.

The industrial production of spirulina (Spirulina and Arthrospira spp.) demands large amounts of carbon and nitrogen. This becomes challenging as raw material costs increase and the worldwide market shifts toward organic products. In this study, we examined the feasibility and effectiveness of various carbon and nitrogen sources in both helical and linear spirulina cultures. Glucose at 2.5 g/L doubled the growth of linear spirulina, and the trichomes were 50% longer and thicker compared to the control (inorganic carbon). In addition, the obtained biomass contained more protein (95% ± 0.2%) and phycobiliproteins (PBPs) (989 ± 12 mg/g). The helical strain preferred a lower glucose concentration (0.5 g/L), which led to a twofold increase in protein content (77% ± 0.4%). On the other hand, the substitution of NaNO₃ with 1% soybean hydrolysate significantly increased the trichome size (500 μm ± 21.34 μm) and PBPs content (847.78 ± 143.9 mg/g) in the linear strain. When cultivated with 0.05% whey or soybean hydrolysate, the helical strain showed a 3.5-fold increase in protein content and a twofold increase in C-phycocyanin and PBPs levels. These findings highlight the robustness of the linear strain, which efficiently used higher organic inputs, whereas the helical strain responded better to lower concentrations of organic C and N.