不同氮素水平对产油尖状栅藻生长及光合生理的影响

在300μmol photons·m^-2·ｓ^-1光照下,以不同初始氮素营养条件的改良BG-11培养基为基础培养基,在Ø6 cm的玻璃柱状光生物反应器通气(加富1.5% CO₂)培养绿藻尖状栅藻(Scenedesmus acuminatus),分析探讨藻细胞的生长及光合生理与氮素营养的关系。结果表明,不同氮素实验组藻细胞的最大生物量有差异,氮浓度为6mmol/L实验组的生物量最高,为5.19g/L。与初始氮浓度18 mmol/L相比,较低的氮浓度9 mmol/L、和 6 mmol/L 在培养前期对尖状栅藻的生长具有明显的促进作用。藻细胞叶绿素a、b及总类胡萝卜素含量与培养液的氮素营养水平呈正相关。低氮条件有利于总脂积累,总脂含量和单位体积总脂产率显著高于全氮组(P<0.05),3.6 mmol/L实验组的总脂含量最高,为干重的54%,比全氮组高17%(P<0.05)。培养后期随着藻细胞总脂的积累,总碳水化合物和总蛋白含量明显下降(P<0.05)。PSⅡ最大光能转化效率(Fv/Fm)、实际光能转化效率(Yield)以及相对电子传递效率(ETR)均随氮素限制而显著下降(P<0.05),光合速率在不同生长阶段呈先上升后下降的趋势,呼吸速率在培养周期内缓慢上升,说明藻的生长、油脂的积累与细胞光合生理状况以及氮素营养水平直接相关。

Effects of Nitrogen Concentration on the Growth and Photosynthetic Physiology of Scenedesmus acuminatus

Scenedesmus acuminatus, a new isolated freshwater green microalga, could be potentially used as feedstock for biodiesel production. The effects of nitrate concentration (3.6 mmol/L, 6 mmol/L, 9 mmol/L, and 18 mmol/L) on the growth and photosynthetic physiology of the algae was investigated with column photobioreactors. The results showed that nitrogen concentration exerted considerable influence on the growth of S. acuminatus, and the maximum biomass of 5.19 g/L was obtained under 6 mmol/L nitrate experimental group. The content of chlorophyll a, b, and total carotenoids of S. acuminatus were positively correlated with nitrogen concentration. The total lipid content of S. acuminatus increased remarkable during the whole culture period, and achieved its peak value of 54% of dry weight, which was 17% higher than that obtained under high nitrogen concentration (18 mmol/L). Meanwhile, the total carbohydrate and protein contents decreased significantly during the whole culture period. The maximum efficiency of light energy conversion of PSⅡ(F_v/F_m), relative electron transfer efficiency (ETR), and the actual energy conversion efficiency(Yield) decreased significantly as the nitrogen supply decreased. The photosynthetic oxygen release rate decreased, with a contrary increase of respiratory rate during the whole culture period. In conclusion, the growth and photosynthetic physiology of S. acuminatus were evidently influenced by the nitrogen concentration, and adjusted to their changing environment.