产油微藻Auxenochlorella protothecoides UTEX 2341对镉胁迫的生理响应及抗性机理

Physiological response and resistance mechanism of oleaginous microalgae Auxenochlorella protothecoides UTEX 2341 under cadmium treatment

摘要:

【背景】重金属镉(Cd)污染问题日益严峻。微藻是一种良好的生物吸附剂。目前研究多关注于微藻对Cd的去除率及吸附性能方面，对其抗Cd机理的研究比较少。【目的】以产油微藻Auxenochlorella protothecoides UTEX 2341为材料，研究Cd胁迫对UTEX 2341生理性状、抗性机理及产油的影响。【方法】测定微藻在0?5 mmol/L Cd胁迫下的生长产油情况，并进一步分析2 mmol/L Cd胁迫下藻体中色素、可溶性蛋白和油脂含量的变化，以及藻体亚显微结构、抗氧化酶和抗氧化剂、脂肪酸组分的改变情况。【结果】Auxenochlorella protothecoides UTEX 2341能够耐受2 mmol/L Cd胁迫，虽然其生物量和叶绿素含量在Cd胁迫下略有降低，但油脂产量显著增加，胁迫168 h时为1.60 g/L，是对照的1.77倍。此外，高浓度Cd引起了胞内活性氧的积累。抗性机理分析表明高Cd胁迫显著抑制了微藻体内的抗氧化酶活性，但非酶抗氧化剂类胡萝卜素和还原性谷胱甘肽的含量显著增加，分别是对照的1.42倍和4.5倍，从而缓解高浓度Cd对微藻细胞造成的氧化损伤，减轻Cd的毒性。脂肪酸组分分析结果表明，Cd胁迫下油酸(C18:1)含量增加，且脂肪酸成分中C16?C18的含量达96%?98%，符合生物柴油的生产标准。【结论】该研究为揭示微藻抗Cd的机理以及Cd胁迫下微藻柴油合成的调控机理提供了一定的研究基础。

Abstract:

[Background] The problem of heavy metal cadmium (Cd) pollution is becoming increasingly serious. Microalgae is a good biological adsorbent of heavy metals. However, current researches have mainly focused on the Cd removal rate and adsorption performance of microalgae, while their anti-Cd mechanisms were seldom studied. [Objective] In our study, the effects of Cd stress on the physiological character, resistance mechanism and oil productivity of oleaginous microalgae Auxenochlorella protothecoides UTEX 2341 were studied. [Methods] The growth and oil productivity of microalgae under 0?5 mmol/L Cd stress were measured. Changes in pigment, soluble protein and oil content of algae under 2 mmol/L Cd stress were further analyzed, as well as changes in their submicrostructure, antioxidant enzymes, antioxidants and fatty acid components. [Results] Auxenochlorella protothecoides UTEX 2341 could withstand 2 mmol/L of Cd stress. Its biomass and chlorophyll content slightly decreased, while its lipid yield significantly increased to 1.60 g/L at 168 h, 1.77 times of the control. Besides, high Cd treatment induced the accumulation of reactive oxygen species (ROS). In response to the oxidative damage caused by high Cd stress, the microalgae cells initiated their resistance mechanism, as the content of antioxidants of carotenoid and reduced glutathione (GSH) remarkably increased to 1.42 and 4.5 times of the control, alleviating the toxicity of Cd, though the activity of antioxidant enzymes was suppressed by Cd stress. According to the results of fatty acid composition analysis, the content of C18:1 increased and the percentage of C16?C18 reached 96%?98%, meeting the production standard of biodiesel. [Conclusion] This research laid a foundation for future researches on the anti-Cd mechanism of microalgae and the algae lipid synthesis regulation mechanism under Cd stress.