Simultaneous Cultivation of Spirulina platensis and the Toxigenic Cyanobacteria Microcystis aeruginosa

Abstract

Mangueira Lagoon, located in the extreme south of Brazil, has water with physicochemical characteristics such as alkaline pH and carbonate levels propitious for the growth of the cyanobacterium Spirulina platensis. Previously published studies have shown that Mangueira Lagoon water supplemented with small quantities of carbon and nitrogen is suitable for S. platensis cultivation and can significantly reduce production costs. We studied mixed cultures of Spirulina platensis and the toxic cyanobacterium Microcystis aeruginosa using a 23 factorial design in which the three factors were the initial biomass concentration of S. platensis and M. aeruginosa and the type of culture medium (100% Zarrouk’s medium or 80% Mangueira Lagoon water plus 20% Zarrouk’s medium). The highest S. platensis maximum specific growth rate (μmax) occurred in the culture with the highest M. aeruginosa biomass concentration and when undiluted culture medium was used (μmax = 0.283 dÐ1). The highest M. aeruginosa specific death rate (k) was obtained in the presence of S. platensis (k = 0.555 dÐ1) and was independent of the initial M. aeruginosa biomass concentration and culture medium, demonstrating that S. platensis cultures are not susceptible to contamination by M. aeruginosa. The culture medium had no significant influence (p > 0.05) on S. platensis μmax values, indicating that production costs could be reduced by using a medium consisting of 80% Mangueira Lagoon water plus 20% Zarrouk’s medium.