氮源类型和水平对3株球状绿藻生长、油脂和花生四烯酸积累的影响

Effects of nitrogen sources and levels on the growth and accumulation of lipids and arachidonic acid of three coccoid green algae

摘要:

【背景】缺刻叶球藻(Lobosphaera incisa Reisigl)是一种单细胞球状绿藻，是已知花生四烯酸(Arachidonic acid，AA)含量最丰富的植物资源之一。然而目前其分类和命名仍然较为混乱。【目的】明确3株球状绿藻(SAG2468、SAG2043、H4301)的分类地位及在不同氮源(硝酸钠、尿素、碳酸氢铵、碳酸铵、硝酸铵、氯化铵和硫酸铵)和氮浓度(18 mmol/L，3 mmol/L)条件下油脂和AA积累的特性。【方法】通过分子系统学和形态观察的方法对3株球状绿藻进行分类界定；采用干重法、重量法和气相色谱分析的方法分别对其生物量、油脂含量、脂肪酸组成及AA含量进行测定。【结果】3株球状绿藻均隶属于叶球藻属(Lobosphaera)，SAG2468原定名为缺刻缘绿藻(Parietochloris incisa)，现修订为缺刻叶球藻(Lobosphaera incisa)，与H4301为缺刻叶球藻的不同地理株系。SAG2043原定名为双隔蚁形藻(Myrmecia bisecta)，现修订为双隔叶球藻(Lobosphaera bisecta)。3株微藻在高氮(18 mmol/L)和低氮(3 mmol/L)浓度的硝酸钠和尿素培养条件下均可良好生长，铵盐对藻细胞生长普遍有抑制作用，且浓度越高抑制作用越显著。低氮胁迫能显著促进油脂和AA的积累(P<0.05)，SAG2043在3 mmol/L硝酸钠条件下油脂和AA产率最高，分别为142.15 mg/(L·d)和35.51 mg/(L·d)，明显高于另外2株微藻(P<0.05)。此时SAG2043对应获得的生物量为4.9 g/L，油脂含量为43.49%，AA含量高达干重的10.86%，占总脂肪酸含量的31.75%。【结论】SAG2043是一株更具AA开发潜力的微藻。

Abstract:

[Background] Lobosphaera incisa Reisigl is a unicellular coccoid green algae, one of the richest plant source of arachidonic acid (AA). However, its taxonomic position has been unclear so far. [Objective] The taxonomy of three coccoid green algae (SAG2468, SAG2043 and H4301) with similar morphology were clarified, and the effects of different nitrogen sources (NaNO3, (NH2)2CO, NH4HCO3, (NH4)2CO3, NH4NO3, (NH4)2SO4 and NH4Cl) and levels (18 mmol/L, 3 mmol/L) on their lipids and AA accumulation were analysed. [Methods] Molecular and morphology identification were used to analyse the taxonomic position of the three strains; dry weight, gravimeter and gas chromatographic analyses were used to determine the biomass concentration and the content of total lipids (TLs) and AA. [Results] The three strains all belonged to the genus of Lobosphaera. Parietochloris incisa SAG2468 was revised to Lobosphaera incisa; SAG2468 and H4301 were the different geographical strains of L. incisa. Myrmecia bisecta SAG2043 was revised to Lobosphaera bisecta. The high (18 mmol/L) and low (3 mmol/L) nitrogen concentration of NaNO3 and (NH2)2CO were all suitable for the growth of these three strains. Ammonium as nitrogen source inhibited the growth of algae, and the higher the concentration, the more inhibition. Low-nitrogen concentration could promote TLs and AA accumulation in all strains significantly (P<0.05). The remarkable TLs and AA volumetric productivities of 142.15 mg/(L·d) and 35.51 mg/(L·d) were obtained in SAG2043 at 3 mmol/L NaNO3, significantly higher than those of H4301 and SAG2468 (P<0.05). Under these conditions, the corresponding biomass concentration was 4.9 g/L, the TLs reached 43.49% and the AA contents were up to 10.86% of dry weight and 31.75% of the total fatty acids in SAG2043. [Conclusion] SAG2043 showed a more prominent advantage to AA production.