Nitrogen supplementation for the production of Chlorella vulgaris biomass in secondary effluent from dairy industry

Abstract

• Secondary effluent from dairy industry was used for Chlorella vulgaris cultivation. • Nitrogen was supplemented for achieving N:P = 1.72:1. • Biomass productivity with effluent was the same as that with standard medium. In this study, secondary effluent from dairy industry was employed for the cultivation of Chlorella vulgaris in a bench-scale tubular photobioreactor. We sought to evaluate the biomass production, the consumption of nitrogen in the medium, and the final biomass composition. Considering the need of nitrogen supplementation, we evaluated the nitrogen:phosphorus ratio: the same proportion found in Bold basal medium (N:P = 1.71:1) and Redfield ratio (N:P = 16:1), comparing with no nitrogen supplementation and Bold Basal Medium. The results showed that nitrogen supplementation improves biomass growth (up to 2824.93 mg.L −1 ), also granting efficient nutrients consumption (up to 98 % of nitrogen removal). Nitrogen supplementation following the Bold medium ratio was the most suitable protocol, since it requires less nitrogen addition without impairment in biomass productivity (Px =259.90 mg.L −1 .d −1 ), in comparison with cultures with supplementation following Redfield ratio (Px =296.73 mg.L −1 .d −1 ) or control culture (Px =221.02 mg.L −1 .d −1 ). In addition, the final biomass showed satisfactory amounts of proteins (up to 21.92 %) and lipids (up to 35.75 %), besides presenting a profile with high concentrations of saturated (C16:0) and monounsaturated fatty acids (C18:1).