High Density Culture Of Flat Photobiorecttor Of Dunaliella Salina

Dunaliella salina is a unicellular eukaryotic green microalgae naturally living in regions with high salinity like ocean and salt lakes.It could synthesize and accumulate large amount of ?-carotene under manual control and stress conditions,therefore it's deemed as the ideal natural resource for artificial production of ?-carotene.America,Israel,Japan,Australia and other countries had successively carried out large-scale researches on the production of ?-carotene with D.salina and commercialized this process gradually.China started relatively late and is short of systematic researches.China possesses good development condition for the production of P-carotene with D.salina due to its long coastline and large number of inland salt lakes.Therefore it's of great significance to study on the high-density and scale cultivation of D.salina for the production of ?-carotene.For the purpose of investigating the improvement conditions for biomass production rate of D.salina and its production rate of ?-carotene,this article optimized the major ingredients of D.salina medium and investigated the optimum concentrations of carbon,nitrogen,phosphorus and salt,based on which optimized the cultivation conditions(light path and cultivation pattern)and light(intensity,quality,UVA,UVB and FR)for scale production using photo-bioreactor to investigate their influences on the growth of D.salina and accumulation of P-carotene.The major results are as follow:1.Carbon,nitrogen,phosphorus and NaCl were the factors with important influences on the growth of D.salina and the synthesis and accumulation of P-carotene.Sodium acetate and sodium nitrate respectively were the optimum carbon source and nitrogen source.The accumulation of ?-carotene was the highest in D.salina which was up to 1.52%of the dry cell weight when the concentration of sodium acetate was 0.02 mmol/L.The accumulation of P-carotene in D.salina was up to 1.76%of the dry cell weight with the production rate of 1.8 mg/L/d when the sodium nitrate in the concentration of 1 mmol/L was used as the nitrogen source,the result of which were significantly higher than those of the experimental groups with urea and ammonium chloride as the nitrogen source.The accumulation and production rate of P-carotene in D.salina were the highest,respectively were 31.29 mg/L and 2.08 mg/L/d,with the phosphorus concentration of 4 mmol/L.2.For the purpose of investigating the comprehensive influences of the concentrations of nitrogen,phosphorus and NaCl in D.salina medium on the growth of D.salina and the accumulation of ?-carotene,Response Surface Analysis(RSM)was applied to analyze the concentrations of NaNO3,NaH2PO4·2H2O and NaCl.Results showed that the accumulation of ?-carotene were the highest when the concentrations of NaNO3,NaH2PO4·2H2O and NaCl respectively were 0.13 g/L,0.085 g/L and 84.25 g/L,under which the biomass was increased by 1.26 times and the accumulation of ?-carotene was increased by 1.83 times compared with the un-optimized groups.3.The high density cultivation result with plate bioreactor showed that cultivation conditions(light path and cultivation pattern)and light(intensity,quality,UVA,UVB and FR)were factors with important influences on the growth of D.salina and accumulation of?-carotene.Due to the special properties(movability and phototaxis)of Dunaliella salina,plate bioreactor with the light path of 5cm was the most suitable for the growth of D.salina.As to the initial investigation on the cultivation pattern(one-time adding,multi-time adding and incomplete change)of D.salina,the result showed that multi-adding pattern was more beneficial for the growth of D.salina.In the light intensity range of 1500-60001ux,the higher intensity of the light,the faster D.salina would grow.Compared with other algae,D.salina possesses better adaptability to high light intensity.Using red light with the wave length of 627 nm,blue light with the wave length of 470 nm,white + red light and white + blue light as the light source,the results of which showed that D.salina could grow normally under red and blue light,but would be obviously prohibited under single light.Cell density would increase under normal light + red light compared with only normal light which implied that red light would promote the growth of D.salina.The cell density didn't increase under normal light + blue light compared with the single normal light which implied that the blue light couldn't obviously promote the growth of D.salina.Adding 5%UVA(with the wave length of 352 nm,370 nm and 395 nm),UVB(with the wave length of 315 nm)and FR(with the wave length of 720 nm)into the red light(with the wave length of 627nm)and the blue light(with the wave length of 470nm),results showed that UVA with different wave lengths displayed non-significant influences on the biomass of D.salina,but showed great influences on the production rate of ?-carotene with significant increase of the production rate.The production rate of ?-carotene increased the most under UVB with the wave length of 390nm which was 0.12 mg/L/d.UVB and FR showed clear prohibition abilities on the biomass of Dunaliella salina and the production rate of ?-carotene.4.The optimized conditions acquired were examined in the bioreactor.The real biomass of the cultivated Dunaliella salina was 3.17 g/L and the accumulation of ?-carotene was 39.24 mg/L which respectively increased by 1.61 times and 2.2 times compared with the former um-optimized conditions.