Effect of Acids on Biomass Growth and Development of Chlorella vulgaris Culture

Background. Influence of dissolved nitrogen and sulfur oxides, as components of flue gases, on the cultivation of microalgae Chlorella vulgaris. Objective. To study biomass production and changes in cells of the microalgae Chlorella vulgaris with the introduction of nitrogen and sulfate acids tor simulate the effects of dissolved nitrogen and sulfur oxides, aiming to develop biotechnology for the utilization of gas emissions by microalgae. Methods. The effect of the constant introduction of small concentrations of nitrogen (up to 0.47%) and sulfate (up to 1.5%) acids on the development of Chlorella vulgaris cultures, pH changes in the cultural envi­ronment, and biomass growth were studied. Results. The utilization of gaseous emissions by Chlorella vulgaris depends on the content of nitrogen and sulfur oxides that are constantly supplied to the cultivation medium, the initial biomass concentration, and pH. It was determined that for an initial cells concentration of (85 ± 5)×104 cells/ml in the culture medium, the threshold values of acids that do not cause significant changes in the cultivation process are 0.1% H₂SO₄ and 0.19% HNO₃. At a sulfuric acid concentration of 0.2%, the culture cells become discolored. Conclusions. It is shown that with a constant supply of sulfuric or nitric acids above the threshold values of 0.1% H2SO4 and 0.19% HNO3, the pH of the culture medium decreases, leading to the suspension of deve­lopment and the death of the Chlorella vulgaris culture. Therefore, controling these parameters will improve the ecological state of the environment and form the basis for developing biotechnology for the utilization of gas emissions by microalgae.