硫素营养水平对产油尖状栅藻光合生理及生化组成的影响

EFFECTS OF SULFUR CONCENTRATION ON THE PHOTOSYNTHETIC PHYSIOLOGY AND BIOCHEMICAL COMPOSITION OF SCENEDESMUS ACUMINATUS

  • 摘要: 以产油尖状栅藻(Scenedesmus acuminatus)为实验材料, 在持续300 μmol photons/(m2·s)光照条件下, 选用3种不同初始Na2SO4浓度(2.0S、1.0S对照、0.25S)的改良BG-11培养基, 在Φ3.0 cm×60 cm光生物反应器中进行通气培养, 研究分析硫素营养水平与尖状栅藻产油过程光合生理和生化组成的关系。实验结果表明, 初始硫素浓度对尖状栅藻生长有显著的影响(P<0.05), Na2SO4初始浓度为2.0S实验组的生物量最高, 为7.47 g/L, 显著高于1.0S组(6.43 g/L)和0.25S组(4.17 g/L)(P<0.05), 说明加富硫素营养可促进藻细胞的生长。尖状栅藻细胞的叶绿素ab以及总类胡萝卜素含量变化均与培养基中初始硫素营养水平呈正相关。在培养初期低硫营养有利于藻细胞快速积累碳水化合物, 0.25S实验组碳水化合物含量最高, 占干重的44.37%, 比1.0S和2.0S组分别高出14.43%和13.78%, 培养后期总碳水化合物和蛋白含量均发生不同程度的降低, 转向大量累积油脂, 0.25S实验组的总脂含量最高, 达55.15% DW, 显著高于1.0S和2.0S组(P<0.05)。藻细胞的光合放氧速率、PSⅡ最大光能转化效率(Fv/Fm)、实际光能转换效率(Yield)以及相对电子传递效率(ETR)均与培养液的初始硫素浓度呈正相关, 在整个培养周期中呈先上升后下降的趋势。77 K低温荧光显示, 尖状栅藻在培养初期2个光系统之间存在光能调配现象。上述结果说明, 尖状栅藻细胞的生长、油脂积累和光合生理状况与硫素营养水平直接相关。

     

    Abstract: Scenedesmus acuminatus microalgae are capable of accumulating lipids when exposed to different sulfur concentrations and are therefore considered promising organisms for biodiesel production. Using column photobiorea-ctors, the relevance of different sulfur concentration (2.0S, 1.0S, and 0.25S) on the growth and photosynthetic physiology of the algae was investigated. The initial sulfur concentration had a significant effect on the growth of S. acuminatus (P<0.05). A maximum biomass of 7.47 g/L was obtained in the 2.0S group, which was significantly higher than that of the 1.0S and 0.25S groups (6.43 g/L and 4.17 g/L, respectively; P<0.05), indicating that the addition of sulfur-rich nutrients could promote algae growth. The changes in chlorophyll and band total carotenoid content in S. acuminatus positively correlated with the initial sulfur level in the medium. At the beginning of cultivation, rapid accumulation of carbohydrates occurred under low sulfur conditions; the 0.25S group achieved the highest carbohydrate content accounting for 44.37% of the dry weight, which was 14.43% and 13.78% higher than that of the 1.0S and 2.0S groups, respectively. With a decreased carbohydrate and protein content, lipid content increased significantly in the later stages of cultivation. The 0.25S group acquired the maximum lipid content (55.15% of the dry weight), which was significantly higher than that of the other two groups (P<0.05). Meanwhile, the photosynthetic oxygen evolution rate, maximum light energy conversion efficiency of PSⅡ (Fv/Fm), actual light energy conversion efficiency (yield), and the relative electron transfer efficiency (ETR) positively correlated with the initial sulfur concentration in the culture medium; the whole culture period showed a tendency to increase first and then significantly decrease. The results of fluorescence emission spectroscopy at 77 K showed that there was light energy allocation between the two photosynthetic systems at the cultivation prophase. In conclusion, growth, lipid accumulation, and photosynthetic physiology of S. acuminatus were apparently influenced by the sulfur concentration.

     

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