Studies On The Effects Of Nutriention On The Growth Of Haematococcus Pluvialis CG-11 And Its Medium Optimization

The fresh-water green unicellular alga Haematococcus pluvialis is considered the most suitable sources of the ketocarotenoid-astaxanthin. A few enterprises have achieved commercial production of astaxanthin by H.pluvialis all over the world. High cell density cultivation of H.pluvialis is one of the production bottlenecks. To achieve this, optimal nutrition requirement and the cultural technology are key points. In this paper, using H.pluvialis CG-11 as experimental material, to select the appropriate growth medium for it and analysis the response of the major nutrient on algal cell growth and physiological characteristics, then to optimize the concentrations of major nutrient in the medium. The main results as follows:1. The growth of H.pluvialis CG-11 under OHM was better than BBM, MAV, MCM, SM, ChenFeng's and Feed Medium, the maximum biomass could achieve 0.87 g·L^-1, which was higher than other mediums notably.2. The influences of single elements such as nitrogen, phosphorus, Mg²⁺, Fe²⁺, EDTA-Na₂ and carbon of OHM were determined respectively. The suitable concentrations were as follows: nitrogen (11.37 mg·L^-1), phosphorus (5.208 mg·L^-1), Mg²⁺ (12.0 mg·L^-1), Ca²⁺ (7.5 mg·L^-1), Fe³⁺(0.5 mg·L^-1), EDTA-Na₂(10 mg·L^-1), C(NaHCO₃ 0.4 g·L^-1, NaAc 3.0 g·L^-1). The maximum biomass of H.pluvialis CG-11 under modified OHM could achieve 1.82 g·L^-1. The increase of the average growth rate and biomass respectly was 15.4% and 41.8% compared with that under original OHM.3. Under phosphorus, Mg²⁺, Fe³⁺-deficiency or sufficiency and nitrogen-deficiency treatments, the fluorescence of PSI (710 nm) decreased while that of PSâ…¡increased. The results predicted that energy distribution between two photosystems was changed. Under Mg²⁺, Fe³⁺-deficiency or sufficiency and phosphorus, nitrogen-deficiency treatments, the fluorescence of CP47 (695nm) decreased significantly, but that of CP43 (685nm) increased relatively, which indicated that energy transfer from CP43 to CP47 was blocked.4. In the bubble column reactor, the effect of ventilation mode on the growth of H.pluvialis CG-11 was studied. The result showed that the growth rate under tube ( d=1mm) treatment was higher than tube (d=5 mm) and gas stone, increase of cell density in the fomer tube were 43.4% and 29.8% respectively, while the biomass were 28.9% and 41.7% respectively. The upper limit of gas entrance velocity of H.pluvialis CG-11 was 14.154 m·s^-1. It made against the growth of green cell when the gas entrance velocitiy was(≥) 21.131 m·s^-1.