The effect of low light flux and nitrogen deficiency on the chemical composition of Spirulina sp. (Arthrospira) grown on digested pig waste

Evaluation of the effect of low light flux and nitrogen deficiency on growth and chemical composition of Spirulina sp. (straight filaments strain, SF) in batch cultures utilizing a complex medium containing sea-water supplemented with anaerobic effluents from digested pig waste, was undertaken. Cultivation was carried out either at a light flux of 66 (lower) or 144 μmol photon m−2 s−1 (higher), utilizing bench raceways. Biomass concentration (as dry weight) after 12 days of cultivation in the complex medium was similar (P<0.05) to the one observed in a chemically defined medium (Zarrouk), regardless of the light intensity. Protein content of the biomass in the complex medium was significantly lower (P<0.05), compared to the Zarrouk medium, regardless of the light flux. However, biomass from the complex medium was enriched in total lipids (28.6%), when cultures were exposed to the lower light flux. On the other hand, the palmitoleic acid percentage of total fatty acids was significantly higher (P<0.05) at a higher light intensity and a high level of gamma linolenic acid (GLA) as a percentage of total fatty acids was observed (28.13%) in the biomass harvested from the complex medium at the lower light intensity. Finally, polysaccharide content was significantly higher (P<0.05) at the high light intensity and a very high content of total polysaccharides (28.41%) was observed in the complex medium.