Enhanced lipid accumulation and biomass yield of Scenedesmus quadricauda under nitrogen starved condition

•2.27-Fold more lipid accumulation of S. quadricauda under nitrogen starved condition.•SGR of 0.33 day−1 and 0.47 doubling per day under N+ condition.•Reduced SGR of 0.14 day−1 with a doubling time of 0.20 under N− condition.•Under nitrogen depleted condition about 25-fold reduction of biomass yield.•Increased L/B ratio (1.11) under nitrogen starved condition.

The experimental results revealed that the 2.27-fold lipid yield was enhanced in nitrogen-depleted condition (226 mg/L) when compared to nitrogen rich condition (99.33 mg/L). Since specific growth rate (SGR) is the single most criteria to decide the biomass yield of microalgae, SGR was analyzed. SGR of 0.33 day−1 was observed with 0.47 doubling per day under nitrogen rich condition. However, low growth rate of 0.14 day−1 with a doubling of 0.20 per day was recorded under nitrogen depleted condition. In accordance with SGR, the dry biomass yield was ranged from 0.055 ± 0.005 to 1.394 ± 0.010 g/L in the presence of nitrogen, indicating the essentiality of major nutrient in the growth medium. The enhanced lipid accumulation under nitrogen starved condition by Scenedesmus quadricauda was perhaps achieved by adopting adverse environmental condition and possible increment in cell size in terms of length/breadth ratio (1.11).