Growth performance and biochemical analysis of the genus Spirulina under different physical and chemical environmental factors

Spirulina is useful to man in many aspects of life including health, food and cosmetics. In the present study, we aimed at investigating the optimum physical and chemical conditions that promote Spirulina mass production by varying a set of physical and chemical parameters, namely pH levels; Mg2+ ion concentration; nitrogen, phosphorous and carbon sources; salinity and different growing media. Temperature, light intensity, and light/dark cycle were maintained at 30°C±2, 4400 lx and 14:10 respectively throughout the study. At pH 9, the dry weight, protein, and chlorophyll a contents were 7.83±0.29 g/L, 1.34±0.12 mg/mL and 18.64±0.06 µg/mL respectively. At 0.8 mmol/L MgO, maximum dry weight, protein, and chlorophyll a contents were obtained. By using NaNO3 as the source of nitrogen, the dry weight was 2.24±0.13 g/L while the protein and chlorophyll a contents were 3.24±0.30 mg/mL and 2.53±0.24 µg/mL respectively. The highest biomass, chlorophyll a and protein contents were obtained by using K2HPO4 as the source of phosphorous. When NaHCO3 was used as the carbon source, the highest dry weight, protein and chlorophyll a yields were observed. Of the growing media used, Zarrouk’s medium yielded the highest biomass protein and chlorophyll a contents. Furthermore, under different salinities, the optimal dry weight, protein and chlorophyll a yields were obtained at 2.5%. This study provides the basis for high biomass production of Spirulina which is a promising microalga endowed with many health benefits due to its high protein content.   Key words: Biomass, chlorophyll a, protein, Spirulina.