High-Resolution Lipidomics Reveals Influence of Biomass and Pretreatment Process on the Composition of Extracted Algae Oils As Feedstock for Sustainable Aviation Fuels.

The increasing demand for sustainable aviation fuel (SAF) creates a need for innovative biomass and lipid sources with compositions that are compatible with refineries. Algae-derived oils present an opportunity to supply a process-compatible lipid feedstock at yields higher than those of conventional oilseed crops. With few documented reports on chemical composition, the process readiness remains elusive. We present data on extraction efficiency, yield, and purity of lipids from algae with and without the application of a low-concentration sulfuric acid pretreatment of the biomass. The pretreatment process increased the oil yield and positively impacted the quality of the extracted oils. Results from fatty acid and lipidomics analysis revealed that the low-lipid biomass sources extracted 70-80% of the available lipids, and the non-fatty acid co-extractants exceeded 40% of the extracted oils. For a high-lipid algae sample, derived from a genetically engineered strain, we show >90% extraction yield with >85% FAME purity. This work provides insights into the composition of algae-derived oils and quality metrics that are essential to determining the viability of lipid hydroprocessing to SAF.

Single-filament imaging mass spectrometry lipidomics in Arthrospira platensis.

RATIONALE: Elucidating intra-organismal biochemical and lipid organization in photosynthetic biological cell factories of filamentous cyanobacteria, such as Arthrospira platensis (Spirulina), is important for tracking physiological response mechanisms during growth. Little is known about the filaments' biochemical organization and cellular structure and no label-free imaging techniques exist that provide molecular mapping. METHODS: We applied ultrahigh-resolution mass spectrometry (MS) with matrix-assisted laser desorption ionization (MALDI) imaging to immobilized Spirulina filaments to investigate the localization of lipids across distinct physiological regions. We optimized matrix selection and deposition methods with the goal of facilitating high spatial, and intra-filament, resolution using untargeted multivariate statistical spectral deconvolution across MS pixels. RESULTS: Our results demonstrate an improved two-step matrix application with an optimized procedure for intra-organismal lipid profiling to improve analyte sensitivity and achieve higher spatial resolution. We evaluate several conventional matrices, namely 2,5-dihydroxybenzoic acid (DHB), superDHB (sDHB), 1,5-diaminonaphthalene (DAN), and a 50:50 mix of DHB and sDHB, and compare delineation and pixel-based elucidation of intra-filament lipidomics. We identified a total of 1626 features that could be putatively assigned a lipid-like formula based on database query and 46 unique features, with associated lipid assignments that were significantly distinct in their intra-filament location. CONCLUSIONS: MALDI imaging MS with untargeted statistical spectral deconvolution was used to visualize intra-filament lipidomics organization in Spirulina filaments. Improvements in matrix deposition, including sequential sublimation and pneumatic spraying, increased signal abundance at high spatial resolution and allowed for identification of distinct lipid composition regions. This work outlines a methodology that may be used for micro-ecological untargeted molecular phenotyping.

Online Coupling of Liquid Chromatography with Fourier Transform Ion Cyclotron Resonance Mass Spectrometry at 21 T Provides Fast and Unique Insight into Crude Oil Composition.

High magnetic field Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry provides the highest mass resolving power and mass measurement accuracy for detailed characterization of complex chemical mixtures. Here, we report the coupling of online liquid chromatography of complex mixtures with a 21 tesla FT-ICR mass spectrometer. The high magnetic field enables large ion populations to be analyzed for each spectrum for a high dynamic range, with 3.2 million mass resolving power at m/z 400 (6.2 s transient duration) or 1.6 million (3.1 s transient duration) while maintaining high mass accuracy for molecular formula assignment (root-mean-square assignment error < 0.150 ppm). Thousands of unique elemental compositions are assigned per mass spectrum, which can be grouped by the heteroatom class, double bond equivalents (the number of rings and double bonds to carbon), and carbon number. Figures of merit are discussed, as well as characterization of an Arabian heavy vacuum gas oil in terms of the ring number, compound class, double bond equivalents, and ion type. Consideration of elemental composition and retention order provides additional structural information.

Combating selective ionization in the high resolution mass spectral characterization of complex mixtures.

Direct "dilute and shoot" mass spectral analysis of complex naturally-occurring mixtures has become the "standard" analysis in environmental and petrochemical science, as well as in many other areas of research. Despite recent advances in ionization methods, that approach still suffers several limitations for the comprehensive characterization of compositionally complex matrices. Foremost, the selective ionization of highly acidic (negative electrospray ionization ((-) ESI)) and/or basic (positive electrospray ionization ((+) ESI)) species limits the detection of weakly acidic/basic species, and similar issues (matrix effects) complicate atmospheric pressure photo-ionization (APPI)/atmospheric pressure chemical ionization (APCI) analyses. Furthermore, given the wide range of chemical functionalities and structural motifs in these compositionally complex mixtures, aggregation can similarly limit the observed species to a small (10-20%) mass fraction of the whole sample. Finally, irrespective of the ionization method, the mass analyzer must be capable of resolving tens-of-thousands of mass spectral peaks and provide the mass accuracy (typically 50-300 ppb mass measurement error) required for elemental composition assignment, and thus is generally limited to high-field Fourier transform ion cyclotron mass spectrometry (FT-ICR MS). Here, we describe three approaches to combat the above issues for (+) ESI, (-) ESI, and (+) APPI FT-ICR MS analysis of petroleum samples. Each approach relies on chromatographic fractionation to help reduce selective ionization discrimination and target either specific chemical functionalities (pyridinic and pyrrolic species (nitrogen) or carboxylic acids (oxygen)) or specific structural motifs (single aromatic core (island) or multi-core aromatics (archipelago)) known to be related to ionization efficiency. Each fractionation method yields a 2-10-fold increase in the compositional coverage, exposes species that are undetectable using direct "dilute and shoot" analysis, and provides coarse selectivity in chemical functionalities that can both increase the assignment confidence and optimize ionization conditions to maximize compositional coverage.

Chromatographic enrichment and subsequent separation of nickel and vanadyl porphyrins from natural seeps and molecular characterization by positive electrospray ionization FT-ICR mass spectrometry.

We report a novel chromatographic method to enrich and separate nickel and vanadyl porphyrins from a natural seep sample and combine molecular level characterization by positive-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Vanadyl and nickel porphyrin model compound elution from primary secondary amine (PSA) stationary phase combined with UV-vis spectroscopy confirms enrichment and subsequent fractionation of nickel and vanadyl porphyrins into polarity-based subfractions. A more than 100-fold increase in signal-to-noise ratio for nickel porphyrins enables unequivocal elemental composition assignment confirmed by isotopic fine structure for all isotopes >1% relative abundance, and the first mass spectral identification of (61)Ni porphyrin isotopologues derived from natural seeps. Oxygen-containing vanadyl porphyrins and sulfur-containing vanadyl porphyrins are isolated in the same fraction simultaneously from the same sample. We provide the first chromatographic evidence of carboxylic acid functionalities peripheral to the porphyrin core, in agreement with previous studies.

Characterization of copolymers and blends by quintuple-detector size-exclusion chromatography.

The properties imparted, oftentimes synergistically, by the different components of copolymers and blends account for the widespread use of these in a variety of industrial products. Most often, however, processing and end-use of these materials (especially copolymers) is optimized empirically, due to a lack of understanding of the physicochemical phase-space occupied by the macromolecules. Here, this shortcoming is addressed via a quintuple-detector size-exclusion chromatography (SEC) method consisting of multiangle static light scattering (MALS), quasi-elastic light scattering (QELS), differential viscometry (VISC), ultraviolet absorption spectroscopy (UV), and differential refractometry (DRI) coupled online to the separation method. Applying the SEC/MALS/QELS/VISC/UV/DRI method to the study of a poly(acrylamide-co-N,N-dimethylacrylamide) copolymer in which both monomer functionalities absorb in the same region of the UV spectrum, we demonstrate how to determine the chemical heterogeneity, molar mass averages and distribution, and solution conformation of the copolymer all in a single analysis. Additionally, through the various mutually independent conformational and architectural metrics provided by combining the five detectors, including the fractal dimension (derived from two different detector combinations), two different dimensionless size parameters, the chemical heterogeneity, and the persistence length, it is shown that the monomeric arrangement is more alternating than random at lower molar masses, thus causing the copolymer to adopt a more extended conformation in solution in this molar mass (M) regime. At high M, however, the copolymer is shown to be and to behave more like a random coil homopolymer, after passing through a 250 kg mol(-1)-broad region of intermediate chain flexibility. Thus, the combination of five detectors provides a unique means by which to determine absolute properties of the copolymer, solution-specific physical behavior, and the underlying chemical basis of the latter. The quintuple-detector method was also extended to the study of blends of polyacrylamide and poly(N,N-dimethylacrylamide) homopolymers to quantitate their molar mass, solution conformation, and chemical heterogeneity and to shed light on the breadth of the distributions of the component species. The method presented should be applicable to the study of copolymers and blends in which either one or both component moieties or polymers absorb in the UV region and can be implemented using not only SEC but other size-based separation methods as well.