The effect of different Nitrogen sources on growth rate and protein content of Spirulina platensis

Nitrogen is known to have a strong influence on the metabolism of lipids and protein in various microalgae. In the present study, the production of S. platensis was optimized in terms of biomass and protein by using different Nitrogen sources as NH_4Cl, NH_4NO_3 and Urea. S. platensis was grown in Zarrouk’s medium in a 3000 ml Erlenmeyer flask, in which the NaNO_3 was replaced by NH_4Cl, NH_4N_O3 and Urea with concentrations of 0.010, 0.025 and 0.050 M. Cultures were incubated at temperature of 30oC, salinity of 25 ppt and initial pH of 9.5 under 12/12 hour light-dark photo period with normal white light. The results clearly showed that S. platensis successfully cultivated by using different Nitrogen regimes, and though the maximum biomass was produced in medium containing NH_4NO_3, but there is not significant differences between treatments (p>0.05). The maximum protein content was obtained in culture containing NH_4NO_3 followed by NH_4Cl and KNO_3, and there is not significant differences between treatments (p>0.05). Moreover, in all S. platensis cultures, increasing in nitrogen concentrations, led to an increase in maximum biomass and protein content. The chl. content increased with increasing Nitrogen concentrations in all treatments and relatively high values (9.18 µg/ml) were found with KNO_3 as a Nitrogen source at 14th day of culturing period. Overall, though the results of present study clearly showed no significant differences between treatments, but using of NH_4NO_3 could have relatively more effectiveness than the other Nitrogen sources.

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