New Mexico State University Nannochloropsis Positive Collection - Mass Spectral Peaklist/Nannochloropsis Positive Ion Mode - Test No. 2 - 300 degrees C

We illustrate a detailed compositional characterization of hydrothermal liquefaction (HTL) oils derived from two biochemically distinct microalgae, Nannochloropsis gaditana and Chlorella sp. (DOE 1412), for a range of reaction temperature as observed by high-resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). The unique capability to unequivocally derive molecular formulae directly from FT-ICR MS-measured mass-to- charge ratio (for several thousand compounds in each oil) shows that lipids are completely reacted/converted for any reaction temperature above 200 degrees C and reveals the formation of non-lipid reaction products with increasing temperature. Specifically, lipid-rich oil is obtained at low reaction temperature (less than 225 degrees C) for both microalgal strains. For positive ion mode, the major lipid components in Chlorella sp. and N. gaditana HTL oils are betaine lipids and acylglycerols, respectively. Acidic species in the HTL oils (observed by negative ion mode) are dominated by free fatty acids (FFA) regardless of reaction temperature. HTL oils obtained at higher-temperatures (ge 225 degrees C) are comprised of a variety of basic nitrogen- and oxygen-containing compounds that originate from protein and carbohydrate degradation at elevated temperature. Similar structural features are observed for the abundant nitrogen heterocyclics between the two strains with slightly lower carbon number for Chlorella sp., overall.

本研究针对两种生化特性迥异的微藻——微拟球藻（Nannochloropsis gaditana）与小球藻属（Chlorella sp.，编号DOE 1412）——所衍生的水热液化（hydrothermal liquefaction, HTL）生物油，开展了基于反应温度梯度的详细组成表征，表征手段为高分辨电喷雾电离傅里叶变换离子回旋共振质谱（high-resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry, ESI FT-ICR MS）。该技术可通过FT-ICR MS测得的质荷比，直接且精准地推导数千种油样组分的分子式。分析结果表明，当反应温度高于200℃时，原料中的脂质可完全反应转化；且随着温度升高，非脂质类反应产物逐步生成。具体而言，两种微藻在低反应温度（低于225℃）条件下，均可获得富含脂质的HTL油。在正离子检测模式下，小球藻属与微拟球藻HTL油中的主要脂质组分分别为甜菜碱脂与酰基甘油。在负离子检测模式下，HTL油中的酸性组分以游离脂肪酸（free fatty acids, FFA）为主，且不受反应温度变化的影响。当反应温度不低于225℃时，所得HTL油主要包含多种含氮、含氧的碱性化合物，这类产物源自高温下蛋白质与碳水化合物的降解。两种微藻的HTL油中均存在大量结构特征相似的含氮杂环化合物，但整体而言小球藻属产物的碳数略低。