Nitrogen effects on proteins, chlorophylls and fatty acids during the growth of Arthrospira platensis.

Spirulina platensis (=Arthrospira platensis) is a tunisian strain which has been isolated for the first time in Oued Essed (Sousse, Sidi Bou Ali). Biomass evolution, proteins, chlorophylls and fatty acids composition of this alga were monitored by varying nitrogen concentrations in the culture medium. Nitrogen stress was provoked by adding sodium nitrate (NaNO3) in the culture medium with concentrations varying from 0 to 5 g/l. Results obtained showed that nitrogen depletion increased total proteins and total chlorophylls. The addition of NaNO3 (5g/l) led to an increase of total fatty acids amounts and modify fatty acids composition. Optimal quantities of palmitic, gamma -linolenic and oleic acids were obtained with NaNO3 free-cultures. Thus, the tunisian strain has valuable biological substances, worthy to determine the optimal conditions for its propagation.

Chlorophylls, proteins and fatty acids amounts of arthrospira platensis growing under saline conditions.

Spirulina platensis (Arthrospira platensis) is a Tunisian strain isolated for the first time, in Tunisia, in Oued Essed (Sidi Bou Ali, in Sousse region). Evolution of biomass, proteins, chlorophylls and fatty acids (FA) has been followed during Spirulina growth. Experiments were carried out by varying sodium chloride concentrations in the culture medium in a range from 1 g L(-1) (natural environment) to 60 g L(-1). Results analysis showed an increase in chlorophyll amounts at 15 g L(-1) NaCl in 10 days old cultures but a decrease at high NaCl concentrations. Optimal proteins amounts was observed at 15 g L(-1) NaCl in young cultures (5 and 10 days). FA composition was modified by NaCl and depended on culture age. Cultures exposed to high salinity concentrations showed not only a decrease in growth rate but also a loss in total fatty acids TFA quantities. Samples cultured over 15 days at 30 g L(-1) NaCl rendered optimal quantities of lipids and gamma-linolenic acid.