LAUSR

Chlorella vulgaris was grown using mixed sources of nitrogen (nitrate and nitrite). Starting from B3N as basal medium, nitrate was substituted by nitrite keeping total nitrogen constant over 7 conditions: 0, 20, 40, 50, 60, 80 and 100% NO2-. Growth rate, nitrogen uptake, photosynthetic apparatus status and pigment contents were monitored. Nitrite addition triggered a growth rate inhibition from early introduction (20% NO2-, 81 mgNO2-/l). Nitrate uptake rate increased with nitrate content in the culture medium (maximum at 5.87 mg/l/Nd, 100% NO3-), while nitrite uptake remained constant around 2.93 mgN/l/d. Photosynthetic apparatus was not impacted by the nitrogen source substitution. Pigments profiles (chlorophyll a, b and total carotenoids) were not statistically different for all the tested conditions. From a biotechnological perspective, this finding rules out the use of nitrite substitution as a pigment manipulating stress strategy.