COMPARATIVE GROWTH ANALYSIS OF SPIRULINA PLATENSIS USING UREA AS A NITROGEN SUBSTITUTE FOR NaNO3

An experiment was conducted in Horticulture Innovation Lab. of Sher-e-Bangla Agricultural University during the period of 1st March 2018 to 15th March 2018 to study the growth performance of microalgae Spirulina platensis with the application of urea as a substitute for NaNO₃. Spirulina was allowed to culture in standard Zarrouks Media (T₀) and three concentrations of Modified Zarrouks Media containing different amounts of urea solution: T₁: 0.60 g/L (0.01M); T₂: 1.20 g/L (0.02M) and T₃: 1.80 g/L (0.03M) substitute for NaNO₃. The growth rate of Spirulina platensis was found to vary in different concentrations of urea solutions. The basic concentration of 4mg/L of inoculum gained maximum cell weight (607 mg/L) in standard Zarrouks Media (T₀) and was significantly (p>0.05) higher than the maximum cell weight (454 mg/L) found in Modified Zarrouks Medium (MZM) containing 0.60 g/L of urea solution (T₁); 1.20 g/L of urea solution (T₂) and 1.80 g/L of urea solution (T₃) respectively on the 12th day of the culture period. Similar trend was also observed in the case of chlorophyll a content and optical density (OD) measurement of Spirulina platensis as well. T₁ showed the best result in the given growth parameters such as specific growth rate (0.086), OD (0.66 mg/L) and chlorophyll a content (7.133 mg/L) in comparison with treatments utilizing the urea solution viz. T₁, T₂ and T₃. These findings may be an effective edition for a cheap but high quality Spirulina production system in Bangladesh by using urea as the readily available nitrogen source.