Photorespirometry is a quick method to assess the effect of several variables on algal growth performances in complex media such as wastewater. In this work, respirometry was applied to derive kinetic parameters of nitrogen exploitation. Oxygen production was found to be related to the internal nitrogen quota, suggesting that the Droop model is more appropriate to describe these systems. The protocol was optimized to minimize the internal N quota in the biomass used for the respirometric tests, so that the half-saturation constant of nutrient uptake could be simply derived. This parameter resulted similar (about 14 mgN L−1) for different nitrogen species (nitrate, ammonium, peptone and urea). The maximum uptake rate cannot be measured with respirometric tests, due to the different stoichiometry of nitrogen species, that affects the yield on oxygen production, but was measured through batch experiments. The preference of microalgae between nitrate and ammonium was ascertained in both batch and continuous reactors. In a continuous system, nitrate is partially removed even when ammonium is present, as a possible result of acclimation phenomena. Finally, mass balances were applied on the continuous systems to derive the value of minimum internal nitrogen quota, that resulted comparable when nitrate or ammonium was supplied.
Application of photorespirometry to unravel algal kinetic parameters of nitrogen consumption in complex media
Pastore M.;Barbera E.;Panichi A.;Sforza E.
2020
Abstract
Photorespirometry is a quick method to assess the effect of several variables on algal growth performances in complex media such as wastewater. In this work, respirometry was applied to derive kinetic parameters of nitrogen exploitation. Oxygen production was found to be related to the internal nitrogen quota, suggesting that the Droop model is more appropriate to describe these systems. The protocol was optimized to minimize the internal N quota in the biomass used for the respirometric tests, so that the half-saturation constant of nutrient uptake could be simply derived. This parameter resulted similar (about 14 mgN L−1) for different nitrogen species (nitrate, ammonium, peptone and urea). The maximum uptake rate cannot be measured with respirometric tests, due to the different stoichiometry of nitrogen species, that affects the yield on oxygen production, but was measured through batch experiments. The preference of microalgae between nitrate and ammonium was ascertained in both batch and continuous reactors. In a continuous system, nitrate is partially removed even when ammonium is present, as a possible result of acclimation phenomena. Finally, mass balances were applied on the continuous systems to derive the value of minimum internal nitrogen quota, that resulted comparable when nitrate or ammonium was supplied.Pubblicazioni consigliate
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