New Mexico State University Chlorella Negative Collection - Mass Spectral Peaklist/Chlorella Negative Ion Mode - Test No. 3 - 250 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.本研究详细表征了两种生化特性迥异的微藻——微拟球藻（Nannochloropsis gaditana）与小球藻属（Chlorella sp.，DOE 1412）所制备的水热液化（hydrothermal liquefaction, HTL）油的组成，并借助高分辨率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）分析了不同反应温度下的产物变化。该技术可直接通过FT-ICR质谱测得的质荷比，精准推导单一样品中数千种组分的分子式，借此可观察到：当反应温度高于200℃时，原料中的脂质会完全反应转化，且随着温度升高会生成非脂质类反应产物。具体而言，两种微藻在较低反应温度（低于225℃）下均可得到富含脂质的HTL油。在正离子模式下，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）。而通过负离子模式检测到的HTL油中酸性组分，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，所得到的HTL油则包含多种由高温下蛋白质与碳水化合物降解生成的碱性含氮、含氧化合物。整体而言，两种微藻的HTL油中均存在大量氮杂环化合物，且结构特征相似，不过小球藻属产物的碳数整体略低。