Effect of Different Nitrogen Sources on the Growth and Lipid Accumulation of Chlorella variabilis

Abstract

Nitrogen is one of the major elements required for growth and other physiological activities of microalgae. Microalgae can use different forms of nitrogen such as nitrate, nitrite, ammonium, and urea. Although the type of nitrogen used by microalgae depends on the species, microalgae usually prefer ammonia as a nitrogen source and the usual order of preference is ammonium, urea, nitrate, and nitrite. However, types of nitrogen sources and their concentrations affect the growth of microalgae cultures and their biochemical structures. It has been reported in many studies that microalgae accumulate more lipids under nitrogen starvation growth conditions. Therefore,growth and lipid accumulation behavior of microalgae Chlorella variabilisin growth medium (BG11) containing different types of nitrogen source [sodium nitrate (NaNO3), ammonium chloride (NH4Cl) and urea(CH4N2O)] was investigated in this work. Maximum cell concentration (1.59 g/L) and growth rate (0.054/h) were obtained in NH4Cl containing photobioreactor, whereas highest lipid content (16.4%) and productivity (4.21 mg/L.day) was obtained in CH4N2O containing photobioreactor. Compared to the other nitrogen sources, NaNO3 did not significantly improve the growth rate and the lipid productivity. According to the results, microalgae can be considered as a raw material for biodiesel production applications in the future.