Biomass production and nutritional properties of Chlorella sorokiniana grown on dairy wastewater

Abstract

This study is a trial to integrate treatment of dairy wastewater (DWW) and bioactive-rich biomass production by Chlorella sorokiniana EAKI cultivated in undiluted and diluted DWW. C. sorokiniana reduced the BOD, COD, nitrate, phosphate, and sulfate content of undiluted DWW by 59.65%, 57.17%, 78.82%, and 88.17%, and 50.22%, respectively. Maximum cell number (7.4 ± 0.03 (log)), biomass production (1.667 ± 0.155 g L−1), biomass productivity (68.116 ± 1.450 mg L−1 d−1), and specific growth rate (0.122 ± 0.008 day−1) were achieved using undiluted DWW cultures. Moreover, higher chlorophyll content (20.642 ± 1.5 mg g−1) and carotenoid content (4.743 ± 0.96 mg g−1) were recorded in cells grown in undiluted DWW. The biomass obtained from mixotrophic cultivation of C. sorokiniana using DWW indicated a high total lipid content of 0.433 ± 0.060 g g−1 DW and total carbohydrate of 0.163 ± 0.005 g g−1 DW while exhibiting low protein level, suggesting the applicability of algal biomass in biofuel production. The highest phenolic content (30.232 ± 1.802 mg GAE g−1 DW) and antioxidant activity (27.725 ± 1.611 μmol TE g−1 DW) were found in microalgae cultured in undiluted DWW. Finally, Pearson’ correlation indicated that the photosynthetic pigments and antioxidant potential of microalgae were the main role promoting the microalgae growth in all experimental groups. Therefore, mixotrophic cultivation of C. sorokiniana by DWW could be an effective approach to decrease the production cost of microalgal biomass rich in bioactive compounds such as antioxidant compounds for animal or aquaculture feed application.