Biochemical response of indigenous microalgal consortia to variations in nitrogen concentration of treated effluent.

Cultivation conditions influence microalgal cellular components, such as lipid accumulation under nutrient depletion, high light irradiation and salinity stress. In this study, indigenous microalgal consortia were cultivated in batch mode using an actual treated effluent. The temporal response of cellular components to the variations in nitrogen concentration and influence of light irradiation on the response were investigated. Prolonged exposure of indigenous microalgal consortia to nitrogen exhaustion had minor effects on total lipid accumulation and enhancement of energy content. Nitrogen replenishment was followed by immediate crude protein accumulation for growth recovery. Total lipid reduction was observed under light and dark conditions after nitrogen replenishment. A one-day lag after nitrogen replenishment in the total lipid reduction was revealed under nitrogen depletion; meanwhile, under nitrogen exhaustion, lipids were utilised as the primary carbon and/or energy source after replenishment, as represented by the decrease from 10.8% to 9.04% within 6 h after the replenishment.