Dunaliella Salina Strain Breeding, Nutrition And Harmful Organism Control

In this paper, we used ultraviolet radiation mutagenesis and monocolony isolation to screen out Dunaliella salina with great biological characters. We expect to obtain strain with high growth rate, highβ-carotene content, good adversity resistance. On the basis of optimized medium, we conducted research of effects of medium adding methods on the biomass increase andβ-carotene cumulation. We experimented on one-time medium addition, multiple-time medium addition and fed-batch culture. We also investigate protozoa and alga pollution problems in the culturing. By doing this, we want to provide experimental support for the bio-pollution treatment in the industrial culturing of Dunaliella salina.We started from D.salinaN8, a strain with highβ-carotene content. By using UV mutation, we screened out two strains, OUC-N8-5 and OUC-N8-2. After growth rate andβ-carotene content measurement, we found growth rate increase on both strains. During the same culturing time, OUC-N8-5 reached a cell density of 153.1×104cell/L and OUC-N8-2 reached a cell density of 123.7×104cell/L, which stands for a 40% and 12% increase from the starting strain (109.3×104cell/L) respectively. Content ofβ-carotene in OUC-N8-5 and OUC-N8-2 has respective value of 10.68mg/L and 9.71 mg/L, which corresponds to 19.5% and 8.7% increase from the starting strain (8.93 mg/L).On the basis of outdoor natural culturing conditions, we used orthogonal design to find optimal nutrient salt condition, and researched the effects of different medium adding methods on the growth rate andβ-carotene content cumulation, aiming to increase cell growth rate andβ-carotene content cumulation by nutritional regulation. While using 15°Be brine as the basic medium, we found that optimal nutrient condition is NaNO3 0.2mmol/L,CO(NH2)2 0.6 mmol/L,NaHCO3 20 mmol/L. Medium adding methods had evident effects on the growth rate andβ-carotene content cumulation. One-time medium addition generated the lowest biomass (25.6×1010cell) andβ-carotene content (15.66g). Fed-batch culture had the highest biomass (47.8×1010cell). Multiple-time medium addition gave the best result for short-termβ-carotene content cumulation (37.08g). Thus, the latter two methods are applicable to achieve high biomass and highβ-carotene content.Furthermore, we conducted research on the treatment of common bio-pollution, ciliates and salt-resistant cyanophyta, in the culture of Dunaliella salina. We achieved 100% death rate of three ciliates by using SDBS with concentration between 3mg/L to 6mg/L. SDBS had limited effect on the growth of Dunaliella salina. Under the highest SDBS concentration (8 mg/L) in the experiments, Dunaliella salina still kept alive with no evident inhibition observed. The experiment results also indicated that copper sulfate had higher toxicity to Aphanothece halophytica Fremy than Dunaliella salina. Copper sulfate with 5 mg/L concentration generated good inhibition and lethal effects, which can be used to purify the algae strain.