Formulation of an Alternative Culture Medium for Arthrospira maxima (Spirulina) Based on “Tequesquite,” a Traditional Mineral Resource

Culture media formulation for Arthrospira maxima (formerly designated as Spirulina maxima) production is a constraining factor. Use of synthetic media could be expensive because most of the commercial strains require salinity conditions higher than 20 g/L. In this study, a traditional, pre-Hispanic mineral resource, known as “tequesquite,” was used as the base for the formulation of an alternative and low-cost culture medium. Tequesquite is available from outcrop areas located in the basin of the former Lake Texcoco, where A. maxima thrived in pre-Hispanic times. The effect on the biomass production of different tequesquite-based formulations, varying N, P, and HCO₃ ^-1, was tested and compared with results obtained with Zarrouk's medium (ZM). Growth of biomass in some alternative formulations showed no significant differences compared with ZM. Production in a bubble-column photobioreactor of the alternative medium reached a maximum of X = 2570.4 mg/L dry weight, compared with X = 2931.4 mg/L dry weight obtained with ZM. The proposed tequesquite-medium formulation has equivalent N and P concentrations as ZM, but only 50% of NaHCO₃, thus reducing the medium's cost. In addition, it avoids the use of seawater or NaCl to provide the salinity condition required for the adequate growth of Arthrospira.