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 (K _s andK _i, respectively) for growth, and the saturation constant (K _m) for NH₄Cl were determined. TheK _s andK _i 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). TheK _m value determined at 122 µmol m⁻² s⁻¹, however, was lower inT. odorata (0.048 µM) than inD. bardawil (0.062 µM).