Nitrate and nitrite as mixed source of nitrogen for Chlorella vulgaris: Growth, nitrogen uptake and pigment contents

Abstract

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.