Effect of nitrogen source and nickel concentration on green microalga Botryococcus braunii growth and its remediation potential

Abstract

The effects of NO3− and/or NH4+, and nickel on the growth and photosynthesis-respiration metabolism of Botryococcus braunii were analyzed. NO3−, NH4+ and Ni(II) removal capacity are described in terms of metabolic and non-metabolic processes. Results demonstrate that B. braunii can live in a pH range from 3 to 9. The total productivity (P) and the productivity of the growth phase (Pv) are higher (≈ 58 and 61 mg L−1 day−1, respectively) when the medium contains NH4+, than when it contains NO3− (≈ 45 and 51 mg L −1 day−1, respectively). NH4+ consumption results in a decrease of the pH of the medium from 7 to 3. Botryococcus braunii reverse the acidic conditions of the medium when NO3− is metabolized (pH from 5 to 8–8.5). Ni(II)-specific removal is mainly due to adsorption and increases along with pH and initial metal concentration. The Hill model best describes the adsorption experimental data. The stoichiometric correlations between H+ desorption and nickel adsorption were 1:5, 1:3 and 1:2 for pH values of 5, 6 and 7, respectively. The present work is a new contribution on the biotechnological potential of B. braunii to live and grow at different pH and to remove NO3−, NH4+, and Ni(II) by metabolic and non-metabolic pathways. Graphical abstract: [Figure not available: see fulltext.].