Improved lipid productivity of Scenedesmus obliquus with high nutrient removal efficiency by mixotrophic cultivation in actual municipal wastewater

Abstract

This study was aimed to assess the growth and lipid productivity improvement of a green microalga Scenedesmus obliquus by mixotrophic cultivation, via addition of sodium acetate (NaAc) into actual municipal wastewater (AMW). Moreover, the nutrient removal efficiency of the culture media in terms of carbon, nitrogen, and phosphorus was investigated. The results showed that the S. obliquus grew better in the AMW than in the BG11 medium (0.20 g L−1 vs 0.16 g L−1 in dry cell weight), and the final algal lipid productivity was higher (9.02 mg L−1 d−1 vs 7.75 mg L−1 d−1, P < 0.05). Further, the addition of NaAc significantly stimulated the algal growth and lipid productivity. Specifically, the highest improvement was obtained by the NaAc-addition of 1 g L−1, where the algal dry cell weight increased 2.40 times than that in the AMW with little organic carbon (0.48 mg L−1 vs 0.20 mg L−1, P < 0.01), and the corresponding algal lipid productivity increased 2.44 time (22.08 mg L−1 d−1 vs 9.02 mg L−1 d−1, P < 0.01). Meanwhile, the addition of 1 g L−1 of NaAc significantly increased the microalga-driven nitrogen and phosphorus removal efficiency, respectively by 1.75 and 2.23 times (82.20% vs 46.85% for total nitrogen, and 76.35% vs 34.18% for total phosphorus). In summary, this study confirmed the feasibility of using organic carbon-supplemented AMW to replace the artificial media for microalgae-based lipid production and nutrient recycling.