Carbon dioxide fixation coupled with ammonium uptake by immobilized Scenedesmus obliquus and its potential for protein production

Abstract

In this study, immobilized Scenedesmus obliquus (S. obliquus) was proposed to simultaneously alleviate the carbon dioxide (CO₂) and ammonium (NH₄⁺-N). Two trophic modes of autotrophy and mixotrophy were conducted by batch experiments with a period of 5 days. The results shown that NH₄⁺-N could be removed more efficiently if algal cells were immobilized, and the trophic mode change had no significant effect on immobilized S. obliquus to NH₄⁺-N removal under 5% CO₂ sparging. Specifically, immobilized S. obliquus could remove NH₄⁺-N completely at initial concentrations of 30 and 50 mg/L and reached about 80% removal rate of NH₄⁺-N at the concentration of 70 mg/L under both trophic modes. The protein synthesis was its main removal mechanism and the dominant amino acid components including glutamic acid (Glu), cystine (Cys), arginine (Arg), methionine (Met) and lysine (Lys) were sensitive to NH₄⁺-N assimilation.

Keywords: Ammonium; Carbon dioxide fixation; Immobilization; Photoautotrophy; Scenedesmus obliquus.