几种环境因子对微拟球藻营养物质积累的影响

为探究光强、光质、氮、磷四种环境因子对微拟球藻营养物质积累的影响,设计以下试验:光强试验设置光强梯度为20、80、140和200 μmol photons·m^-2·s^-1;光质试验依照RGB原理,调节红、蓝、绿光比例分别为100%、50%、0%;氮浓度试验设置氮浓度梯度为55.40、13.85、3.46、1.73 mg·L^-1;磷浓度试验设置磷浓度梯度为8.96、2.24、0.56、0.28 mg·L^-1,统一初始接种密度并测定25 d时脂肪酸及色素组成、蛋白及可溶性糖浓度。结果显示,蛋白和可溶性糖浓度随着光强的增大而增大;200 μmol photons·m^-2·s^-1 光强下微拟球藻生长速率最快、生物量最高,且蛋白(5.17 mg·mL^-1)和可溶性糖(2.40 mg·mL^-1) 浓度最大;20 μmol photons·m^-2·s^-1光强下叶绿素a比例最大。光质试验表明,红光对于微拟球藻可溶性糖积累和生长有一定促进作用,其余光质比例对其生长无显著影响,绿光有利于β-胡萝卜素积累,但纯绿光显著抑制蛋白合成。氮浓度为55.40 mg·L^-1时微拟球藻不饱和脂肪酸和二十碳五烯酸占比均达到最大,分别为68.23%和20.50%,且随着氮浓度降低,微拟球藻生长速率、蛋白及还原糖含量均显著降低。同样,随着磷浓度降低,微拟球藻生长速率和蛋白含量均显著下降,磷浓度为2.24 mg·L^-1时更适宜积累可溶性糖。本研究可为微拟球藻在不同环境因子下的营养优化培养提供理论支撑,具有一定的应用意义和经济价值。

Effects of Several Environmental Factors on Nutrient Accumulations of Nannochloropsis oceanica

To explore effects of light intensity, light quality, nitrogen, and phosphorus on nutrient accumulations inNannochloropsis oceanica, this study was designed into four parts as followed. The light intensity was set as 20, 80, 140 and 200 μmol photons·m^-2·s^-1, respectively, in the light intensity experiment. In the part of light quality, ratios of red-blue-green light were adjusted to 100%, 50% and 0%, respectively, according to the RGB principle. Nitrogen concentration was set as 55.40, 13.85, 3.46 and 1.73 mg·L^-1 in the nitrogen experiment, respectively. Phosphorus concentration was set to 8.96, 2.24, 0.56 and 0.28 mg·L^-1 in the phosphorus experiment, respectively. The initial inoculation density was unified and the composition of fatty acids, pigment, protein, and soluble sugar were measured after 25 days. At the light intensity of 200 μmol photons·m^-2·s^-1, N. oceanicaobtained the fastest growth rate, the highest biomass; besides, the concentration of protein (5.17 mg·mL^-1), and soluble sugar (2.40 mg·mL^-1) is the greatest. At the light intensity of 20 μmol photons·m^-2·s^-1, the ratio of chlorophyll a was the highest. Overall, the contents of protein and soluble sugar increased with light intensity. The light quality experiment showed that the red light had a certain effect on promoting the growth and soluble sugar accumulation, while blue and green lights did not. Results also suggested that the green light was conducive to β-carotene accumulation, but 100% green light significantly inhibited the growth of N. oceanica. At the nitrogen concentration of 55.40 mg·L^-1, the proportions of unsaturated fatty acids and eicosapentaenoic acid (EPA) of N. oceanicareached the maximum, which were 68.23% and 20.50%, respectively. With the nitrogen concentration declining, the growth rate, protein, and soluble sugar inN. oceanicasignificantly decreased. Similarly, with the phosphorus concentration declining, the growth rate and protein content significantly decreased. The phosphorus concentration of 2.24 mg·L^-1 was beneficial to soluble sugar accumulation. This study provides theoretical support for optimizing the cultivation of N. oceanica under different environmental factors, which has certain practical significance and economic value.