The impact of auxin analogues on microalgal intracellular component accumulation and nutrient removal for mariculture wastewater treatment basing on bacterial-algal coupling technology

Abstract

Acidogenic fermentation coupled with microalgae cultivation is a promising approach for mariculture wastewater (MW) treatment. However, the low biomass and lipid production of microalgae restrict its practical application. In this study, auxin analogues including α-naphthylacetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D) and indomethacin were applied to the cultivation of Chlorella pyrenoidosa under mixotrophic condition. The effects of auxin analogues on microalgal growth, intracellular component accumulation and nutrient removal were evaluated. The optimal growth and intracellular composition accumulation of Chlorella pyrenoidosa were obtained at 2 mg L−1 NAA, 1 mg L−1 indomethacin, and 1 mg L−1 2,4-D. NAA was more efficient than indomethacin and 2,4-D for lipid production, and the maximum lipid accumulation reached 52% with 2 mg L−1 NAA. Auxin analogues enhanced the uptake of volatile fatty acids, ammonium and phosphate from acidogenic fermentation effluent, attributed to the improvement of microalgal growth. This study provided a new insight for enhancing mariculture wastewater treatment with mixotrophic microalgae.