富里酸诱导对三角褐指藻EPA合成积累的影响

Effects of fulvic acid induction on eicosapentaenoic acidaccumulation in Phaeodactylum tricornutum

摘要:

探究不同富里酸作用浓度对三角褐指藻二十碳五烯酸（EPA）合成积累的影响。结果表明，在20 mg/L富里酸诱导下，三角褐指藻EPA含量和产量均达到最大值，为19.81 g/100 g和738.91 mg/L，较无富里酸诱导EPA含量和产量分别提高2.01和2.54倍。外源富里酸作用提高了三角褐指藻胞内过氧化物酶（POD）、超氧化物歧化酶（SOD）、过氧化氢酶（CAT）酶活，使得色素和多酚抗氧化组分比例增加，活性氧（ROS）和丙二醛（MDA）水平降低，整体抗氧化能力获得显著提升，有效阻抑EPA的氧化分解；富里酸作用同时还上调了EPA合成通路脱饱和酶（Δ5-FADS、Δ6-FADS、Δ12-FADS、Δ15-FADS、Δ17-FADS）和延长酶（Δ6-ELOVL）等系列关键酶，使其上调表达量较无富里酸作用分别增加1.27、1.81、1.24、1.45、1.43和1.46倍，为EPA高效合成积累提供前驱物和能量。富里酸作用效果协同强化了三角褐指藻EPA合成积累效率。

Abstract:

The objective of this work was to investigate the effects of different fulvic acid (FA) concentrations on eicosapentaenoic acid (EPA) accumulation in Phaeodactylum tricornutum. The results showed that 20 mg/L FA treatment induced the highest EPA content and EPA productivity by 19.81 g/100 g and 738.91 mg/L, represented 2.01- and 2.54-fold more than that without FA treatment group. The exogenous FA treatment intensified activities of POD, SOD, and CAT in P. tricornutum to enhance the proportions of pigments and polyphenol simultaneously decrease the levels of ROS and MDA. This indicated that the antioxidative capacities of P. tricornutum cells were significantly improved consequently inhibited oxidative decomposition of EPA. FA treatment also caused up-regulations of Δ5-FADS、Δ6-FADS、Δ12-FADS、Δ6-ELOVL、Δ15-FADS、Δ17-FADS involved in EPA pathway resulting in 1.27-, 1.81-, 1.24-, 1.45-, 1.43- and 1.46-fold increments than that without FA treatment group. The enhancement of these crucial enzymes in EPA pathway would provide a majority of precursors and energy for efficient EPA synthesis. Consequently, EPA accumulation in P. tricornutum-treated with FA attributed to inhibition of oxidative decomposition of EPA and supplementations of precursors/energy.