A Study Of The Optimal Cultivation Conditions Of Cr Enrichment By Dunaliella Salina And Chlorella Pyrenoides

In this paper, we used Chlorella pyrenoides and Dunaliella salina as experimental material to assess the optimal cultivation conditions of Cr enrichment by the two alga species through cultivation experiments by Cr3+ addition in the medium. Chlorella pyrenoides was cultivated under the 7 different concentrations of Cr3+ and Dunaliella salina was cultivated under the 8 different concentrations of Cr3+. We measured biomass (cell density) of the two algae, the amount of Cr3+ enrichment, contents of chlorophyll-a, β -carotene, intracellular protein and carbohydrate in the different Cr3+ addition treatments. Based on these experiments, we used orthogonal experiment with three factors and three levels, analyzed the effects of different methods of Cr3+ addition on algal biomass and Cr enrichment and discussed the dynamic processes of Cr3+ enrichment under the optimal combination conditions. In addition, the effects of Cr3+ enrichment on the algal cell molecular functional group structure were also investigated. The result of this study indicated that Cr3+ significantly increased the biomass of Chlorella pyrenoides and its contents of chlorophyll-a, β -carotene, protein and carbohydrate at the Cr3+ concentration of Img ?L"-1. The optimal concentration of Cr3+ was Img ?L-1 that should be added day by day to the medium during the initial 5d of culture. At this condition, harvested biomass and Cr enrichment quantity of Chlorella pyrenoides were 2.25mg ?mL-1 and 82.89 *g ?g-1, respectively, with an enrichment efficiency of 88.7%. The optimal combination of temperature, pH and N, P concentration depended on the experimental intention. To improve the growth and Cr3+ enrichment of Chlorella pyrenoides, the optimal combination of temperature, pH and N, P concentration is 30 ℃ in temperature, 7 in pH, 3g ?L-1 in N concentration and .08g 'L-1 in P concentration, with the highest biomass of 2.38mg 'mL-1 and the highest enrichment quantity of 85.35 * g ?g-1. The concentration of 0.2mg ?L-1 in Cr3+ can significantly increased the biomass of Dunaliella salina and its contents of chlorophyll-a, 3 -carotene, protein and carbohydrate. The optimal concentration of Cr3+ was 0.2mg ?L-1 that should be added day by day to the medium during the initial 8d of culture. At this condition, harvested biomass and Cr enrichment quantity of Dunaliella salina were 0.93mg ?mL-1 and 40.23 * g ?g-1, respectively, with an enrichment efficiency of 90.6%. The optimal combination is 30℃ in temperature, 7 in pH and 70 %o in salinity because the highest biomass of 0.98mg ?mL-1 and the highest enrichment quantity of 42.77 μ g ?g-1.