迦得拟微球藻在不同硝酸钾浓度下的生长和生理生化特征

THE GROWTH,PHYSIOLOGICAL AND BIOCHEMICAL CHARACTERISTICS OF NANNOCHLOROPSIS GADITANA IN DIFFERENT POTASSIUM NITRATE CONCENTRATION

迦得拟微球藻(Nannochloropsisgaditana)具有较高的开发价值,但对于其活性物质定向积累的研究相对较少。本文以迦得拟微球藻为研究对象,设置3.0、5.0、7.5和14.9mmol/L (对照组,ASW培养基的硝酸钾浓度)四种硝酸钾组,探究氮素水平调控迦得拟微球藻总脂、多糖、可溶性蛋白和多不饱和脂肪酸等物质定向积累的可行性,以及此过程藻细胞的光合生理响应规律。结果表明:与对照组相比,硝酸钾浓度降低,迦得拟微球藻的生物量降低、总脂含量增加、可溶性蛋白质含量和多糖含量降低,然而其总脂、多糖与可溶性蛋白产率的最大值却在对照组条件下获得,分别为0.150、0.170和0.053g/(L·d);与对照组相比,3.0、5.0和7.5mmol/L处理组的C20:5相对含量分别降低73.1%、49.1%和23.9%;迦得拟微球藻的主要色素(堇菜黄素、无隔藻黄素、β-胡萝卜素、叶绿素a)随氮浓度降低呈减少趋势;PSⅡ最大光量子产量(Fv/Fm)、相对电子传递效率(rETR)和光合放氧速率随氮浓度降低而显著降低。综上所述,调控氮浓度可以实现迦得拟微球藻总脂、可溶性蛋白、多糖和C20:5的定向积累,但上述物质的产率却受到生物质浓度的影响,14.9mmol/L氮浓度条件下高光合效率是迦得拟微球藻获得较高活性物质产率的主要原因。

Nannochloropsis is a high-valued microalga but few studies on the targeted accumulation of active substances are reported.To investigate the targeted accumulation of lipids,polysaccharides,proteins,and fatty acid profiles,as well as the photosynthetic physiological response,we cultivated Nannochloropsis gaditana in ASW medium under different KNO3 concentrations(14.9,7.5,5.0,and 3.0 mmol/L,and the normal concentration of the ASW medium as the control group).Our results showed that,with the decrease in KNO3 concentration,the total lipid content increased and the biomass concentration,the soluble protein,and polysaccharide contents decreased compared with those of the control.However,the maximum productivities of total lipids,polysaccharides,and soluble proteins occurred in the control,being 0.150,0.170,and 0.053 g/(L·d),respectively.The relative contents of C20:5 in the 3.0,5.0,and 7.5 mmol/L treatment groups decreased by 73.1%,49.1%,and 23.9%,respectively,compared to the control.The main pigment contents,including violaxanthin,vaucheriaxanthin,β-carotene,and chlorophyll a,declined as the nitrogen concentration decreased.The maximal photochemical efficiency of PS Ⅱ(Fv/F m),relative electron transport rate(rETR),and photosynthetic oxygen evolution rate were correlated positively with nitrogen concentration.Therefore,the nitrogen concentration could control the targeted accumulation of total lipids,soluble proteins,polysaccharides,and C20:5 of N.gaditana,while the biomass concentration of these substances affected their productivity.In this research,the high active substance productivity of N.gaditana under 14.9 mmol/L nitrogen concentration was due to a high photosynthetic efficiency.