New Mexico State University Nannochloropsis Positive Collection - Mass Spectral Peak list/Nannochloropsis Positive Ion Mode - Test No. 1 - 275 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.

本研究详细表征了源自两种生化特性迥异的微藻菌株——微拟球藻（Nannochloropsis gaditana）与小球藻属（Chlorella sp.，DOE 1412）的水热液化（hydrothermal liquefaction, HTL）油的组成特征，采用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），在一系列反应温度条件下完成表征。该技术可直接通过FT-ICR MS测得的质荷比，明确推导单份油样中数千种化合物的分子式，结果显示，当反应温度高于200℃时，脂质可完全反应转化，且随着温度升高会生成非脂质类反应产物。具体而言，两种微藻在低于225℃的低温反应条件下，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（betaine lipids）与酰基甘油（acylglycerols）。通过负离子检测模式观测到的HTL油酸性组分，无论反应温度如何，均以游离脂肪酸（free fatty acids, FFA）为主。当反应温度≥225℃时，所得HTL油包含多种碱性含氮、含氧化合物，这些化合物源自高温下蛋白质与碳水化合物的降解。整体而言，两种微藻的HTL油中均存在大量氮杂环化合物，结构特征相似，但小球藻属样品的碳数略低。