New Mexico State University Nannochloropsis Positive Collection - Mass Spectral Peaklist/Nannochloropsis Positive Ion Mode - Test No. 3 - 200 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.，DOE 1412），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），对其水热液化（hydrothermal liquefaction, HTL）油的组成特征随反应温度的变化规律开展详细表征。该质谱技术具备直接通过FT-ICR MS测得的质荷比（mass-to-charge ratio）明确推导每种油样中数千种化合物分子式的独特能力，据此发现：当反应温度高于200℃时，脂质完全发生反应转化；且随着反应温度升高，体系中会生成非脂质类反应产物。具体而言，两种微藻在低于225℃的较低反应温度下均可获得富含脂质的HTL油产物。在正离子检测模式下，小球藻属（Chlorella sp.）与微拟球藻（N. gaditana）的HTL油中主要脂质组分分别为甜菜碱脂（betaine lipids）与酰基甘油（acylglycerols）。在负离子检测模式下观测到的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油主要包含多种由高温下蛋白质与碳水化合物降解产生的含氮、含氧碱性化合物。整体而言，两种微藻的HTL油中均存在大量含氮杂环化合物，且小球藻属（Chlorella sp.）的含氮杂环化合物碳数整体略低于微拟球藻。