Effect of light intensity and ammonium-N on carotenogenesis ofTrentepohlia odorata andDunaliella bardawil

Abstract

AxenicTrentepohlia odorata was cultured at three different NH4Cl levels (3.5 × 10−2, 3.5 × 10−3, 3.5 × 10−4 M) and three different light intensities (48, 76, 122 µmol m−2 s−1). Chloride had no effect on growth over this range of concentration. High light intensity and high NH4Cl concentration enhanced the specific growth rate. The carotenoid content increased under a combination of high light intensity and low N concentration. WhenD. bardawil was exposed to the same combination of growth conditions, there was an increase in its carotenoid content. The light saturation and the light inhibition constants (Ks andKi, respectively) for growth, and the saturation constant (Km) for NH4Cl were determined. TheKs andKi values were higher inT. odorata (66.7 and> 122 σmol m−2 s−1, respectively) than inD. bardawil (5.1 and 14.7 µmol m−2 s−1, respectively). TheKm value determined at 122 µmol m−2 s−1, however, was lower inT. odorata (0.048 µM) than inD. bardawil (0.062 µM).