Effective C–N–P ratio for growth and nutrient removal efficiency of Scenedesmus obliquus in sugar mill effluent

Microalgae grown heterotrophically are reported to grow well and yield more biomass and metabolites when compared to photoautotrophic cultivation. In the present study, the growth of Scenedesmus obliquus in solution containing glucose, urea, and diammonium phosphate as carbon (0.2–1.0 %), nitrogen (0.07–0.21 %) and phosphorus (0.04–0.12 %) sources was evaluated. While complete utilization of carbon and nitrogen at all concentration was observed on the third day, complete phosphate uptake by the microalga was observed only at 0.04 and 0.08 % concentrations. The microalga grown with C–N–P ratio of 0.2:0.14:0.08 % showed maximum biomass yield (1.23 g L⁻¹) in 5 days. Furthermore, the microalga was found to adapt itself to the heterotrophic mode of growth when cultivated in the sugar mill effluent with a sugar concentration of 1.8 g L⁻¹. Despite the complex characteristics of the substrate, S. obliquus exhibited maximum biomass yield of 1.28 g L⁻¹ with 55 and 31 % total protein and carbohydrate, respectively, in 12 days. Significant reduction in most of the physico-chemical parameters demonstrates the bioremediation potential of S. obliquus.