Optimization of a single phase method for lipid extraction from milk

Microalgae to bioenergy production: Recent advances, influencing parameters, utilization of wastewater - A critical review

Fossil fuel limitations and their influence on climate change through atmospheric greenhouse gas emissions have made the excessive use of fossil fuels widely recognized as unsustainable. The high lipid content, carbon-neutral nature and potential as a biofuel source have made microalgae a subject of global study. Microalgae are a promising supply of biomass for third-generation biofuels production since they are renewable. They have the potential to produce significant amounts of biofuel and are considered a sustainable alternative to non-renewable energy sources. Microalgae are currently incapable to synthesize algal biofuel on an extensive basis in a sustainable manner, despite their significance in the global production of biofuels. Wastewater contains nutrients (both organic and inorganic) which is essential for the development of microalgae. Microalgae and wastewater can be combined to remediate waste effectively. Wastewater of various kinds such as industrial, agricultural, domestic, and municipal can be used as a substrate for microalgal growth. This process helps reduce carbon dioxide emissions and makes the production of biofuels more cost-effective. This critical review provides a detailed analysis of the utilization of wastewater as a growth medium for microalgal - biofuel production. The review also highlights potential future strategies to improve the commercial production of biofuels from microalgae.

Mass Spectrometry-Based Multi-omics Integration with a Single Set of C. elegans Samples

Mass spectrometry-based large-scale multi-omics research has proven to be powerful in answering biological questions; nonetheless, it faces many challenges from sample preparation to downstream data integration. To efficiently extract biomolecules of different physicochemical properties, preparation of various sample type needs specific tailoring, especially of difficult ones, such as Caenorhabditis elegans. In this study, we sought to develop a multi-omics sample preparation method starting with a single set ofC. elegans samples to save time, minimize variability, expand biomolecule coverage, and promote multi-omics integration. We investigated tissue disruption methods to effectively release biomolecules and optimized extraction strategies to achieve broader and more reproducible biomolecule coverage in proteomics, lipidomics, and metabolomics workflows. In our assessment, we also considered speediness and usability of the approaches. The developed method was validated through a study of 16C. elegans samples designed to shine light on mitochondrial unfolded protein response (UPRmt), induced by three unique stressors─knocking down electron transfer chain element cco-1, mitochondrial ribosome protein S5 mrps-5, and antibiotic treatment Doxycycline. Our findings suggested that the method achieved great coverage of proteome, lipidome, and metabolome with high reproducibility and validated that all stressors triggered UPRmt in C. elegans, although generating unique molecular signatures. Innate immune response was activated, and triglycerides were decreased under all three stressor conditions. Additionally, Doxycycline treatment elicited more distinct proteomic, lipidomic, and metabolomic response than the other two treatments. This method has been successfully used to process Saccharomyces cerevisiae (data not shown) and can likely be applied to other organisms for multi-omics research.

Analysis of milk with liquid chromatography–mass spectrometry: a review

As a widely consumed foodstuff, milk and dairy products are increasingly studied over the years. At the present time, milk profiling is used as a benchmark to assess the properties of milk. Modern biomolecular mass spectrometers have become invaluable to fully characterize the milk composition. This review reports the analysis of milk and its components using liquid chromatography coupled with mass spectrometry (LC–MS). LC–MS analysis as a whole will be discussed subdivided into the major constituents of milk, namely, lipids, proteins, sugars and the mineral fraction.

Rapid Multi-Omics Sample Preparation for Mass Spectrometry

Multi-omics analysis is a powerful and increasingly utilized approach to gain insight into complex biological systems. One major hindrance with multi-omics, however, is the lengthy and wasteful sample preparation process. Preparing samples for mass spectrometry (MS)-based multi-omics involves extraction of metabolites and lipids with organic solvents, precipitation of proteins, and overnight digestion of proteins. These existing workflows are disparate and laborious. Here, we present a simple, efficient, and unified approach to prepare lipids, metabolites, and proteins for MS analysis. Our approach, termed the Bead-enabled Accelerated Monophasic Multi-omics (BAMM) method, combines an n-butanol-based monophasic extraction with unmodified magnetic beads and accelerated protein digestion. We demonstrate that the BAMM method affords comparable depth, quantitative reproducibility, and recovery of biomolecules as state-of-the-art multi-omics methods (e.g., Matyash extraction and overnight protein digestion). However, the BAMM method only requires about 3 h to perform, which saves 11 steps and 19 h on average compared to published multi-omics methods. Furthermore, we validate the BAMM method for multiple sample types and formats (biofluid, culture plate, and pellet) and show that in all cases, it produces high biomolecular coverage and data quality.

Comparison of Workflows for Milk Lipid Analysis: Phospholipids

Milk is a rich source of lipids, with the major components being triglycerides (TAG) and phospholipids (mainly phosphatidylcholine (PC), sphingomyelin (SM), phosphatidylethanolamine (PE), phosphatidylserine (PS) and phosphatidylinositol (PI)). Liquid chromatography-mass spectrometry (LC-MS) is the predominant technique for lipid identification and quantification across all biological samples. While fatty acid (FA) composition of the major lipid classes of milk can be readily determined using tandem MS, elucidating the regio-distribution and double bond position of the FA remains difficult. Various workflows have been reported on the quantification of lipid species in biological samples in the past 20 years, but no standard or consensus methods are currently available for the quantification of milk phospholipids. This study will examine the influence of several common factors in lipid analysis workflow (including lipid extraction protocols, LC stationary phases, mobile phase buffers, gradient elution programmes, mass analyser resolution and isotope correction) on the quantification outcome of bovine milk phospholipids. The pros and cons of the current LC-MS methods as well as the critical problems to be solved will also be discussed.

Optimizing accelerated solvent extraction combined with liquid chromatography-Orbitrap mass spectrometry for efficient lipid profile characterization of mozzarella cheese

In this study, a novel Accelerated Solvent Extraction (ASE) procedure combined with UHPLC-Q-Orbitrap-MS was developed for detailed untargeted lipid profile of mozzarella cheese. Response Surface Methodology and Pareto front, using a Central Composite Design (CCD), were employed to define the optimised combination of extraction temperature, number of extraction cycles and mix of solvents. LipidSearch™ software was used for a reliable and accurate lipid identification. A total of 13 subclasses, including ceramides, diacylglycerols, triacylglycerols, lysophosphatidylcholines, lysophosphatidylethanolamines, phosphatidylcholines, phosphatidylethanolamines, phosphatidylinositols, sphingomyelins, bismethyl phosphatidic acids, cholesterol ester, zymosterol ester, hexosyl ceramides were measured. The elaboration of the CCD showed that the solvents ratio was the main factor affecting the extraction efficiency. The optimised ASE method, together with the Folch extraction, synergistically contributed to a complete characterization of lipid profile of mozzarella cheese, confirming ASE technique, associated with high resolution mass spectrometry detection, as an efficient tool for Lipidomics in food science.

Advances in Lipid Extraction Methods-A Review

Extraction of lipids from biological tissues is a crucial step in lipid analysis. The selection of appropriate solvent is the most critical factor in the efficient extraction of lipids. A mixture of polar (to disrupt the protein-lipid complexes) and nonpolar (to dissolve the neutral lipids) solvents are precisely selected to extract lipids efficiently. In addition, the disintegration of complex and rigid cell-wall of plants, fungi, and microalgal cells by various mechanical, chemical, and enzymatic treatments facilitate the solvent penetration and extraction of lipids. This review discusses the chloroform/methanol-based classical lipid extraction methods and modern modifications of these methods in terms of using healthy and environmentally safe solvents and rapid single-step extraction. At the same time, some adaptations were made to recover the specific lipids. In addition, the high throughput lipid extraction methodologies used for liquid chromatography-mass spectrometry (LC-MS)-based plant and animal lipidomics were discussed. The advantages and disadvantages of various pretreatments and extraction methods were also illustrated. Moreover, the emerging green solvents-based lipid extraction method, including supercritical CO2 extraction (SCE), is also discussed.

Comprehensive and High-Coverage Lipidomic Analysis of Oilseeds Based on Ultrahigh-Performance Liquid Chromatography Coupled with Electrospray Ionization Quadrupole Time-of-Flight Mass Spectrometry

Oilseeds are an important source of dietary lipids, and a comprehensive analysis of oilseed lipids is of great significance to human health, while information about the global lipidomes in oilseeds was limited. Herein, an ultrahigh-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry method for comprehensive lipidomic profiling of oilseeds was established and applied. First, the lipid extraction efficiency and lipid coverage of four different lipid extraction methods were compared. The optimized methyl tert-butyl ether extraction method was superior to isopropanol, Bligh-Dyer, and Folch extraction methods, in terms of the operation simplicity, lipid coverage, and number of identified lipids. Then, global lipidomic analysis of soybean, sesame, peanut, and rapeseed was conducted. A total of 764 lipid molecules, including 260 triacylglycerols, 54 diacylglycerols, 313 glycerophospholipids, 36 saccharolipids, 35 ceramides, 30 free fatty acids, 21 fatty esters, and 15 sphingomyelins were identified and quantified. The compositions and contents of lipids significantly varied among different oilseeds. Our results provided a theoretical basis for the selection and breeding of varieties of oilseed as well as deep processing of oilseed for the edible oil industry.

Bovine Milk Triacylglycerol Regioisomer Ratio Shows Remarkable Inter-Breed and Inter-Cow Variation

Regioisomers (or positional isomers) of triacylglycerols (TAGs) of milk are known to show differential outcome in relation to human absorption. Quantitation of TAG regioisomers remains a big challenge due to the lack of facile chromatographic separation technique. The feasibility of using fragment ion intensity ratio to determine the ratio of co-eluting AAB/ABA-type regioisomer pairs was confirmed in this study. The ability of C30 stationary phase in resolving interfering TAG isomers was demonstrated for the first time. This allowed us to reveal the complexity of using fragment ion intensity to quantify 1,2-olein-3-palmitin (OOP), 1,3-olein-2-palmitin (OPO), 1,2-olein-3-stearin (OOS), and 1,3-olein-2-stearin (OSO) regioisomers in milk samples. A novel algorithm was proposed to consider the contribution of OPO/OOP and OSO/OOS double bond (DB)-isomers and to eliminate the interference of isobaric ions from other isomers, an aspect overlooked in previous studies. This liquid chromatography-mass spectrometry method that requires no pre-fractioning and a moderate chromatographic separation time of 36 min is simple and, thus, suitable for screening a large number of samples for genetic analysis of this trait. Preliminary results using a small cohort of animals showed that OPO/OOP ratio differs significantly between Jersey and Holstein cows, and a large variation was also observed across individual Holstein cows.

A Novel Solid Phase Extraction Sample Preparation Method for Lipidomic Analysis of Human Plasma Using Liquid Chromatography/Mass Spectrometry

Lipidomic approaches are widely used to investigate the relationship between lipids, human health, and disease. Conventional sample preparation techniques for the extraction of lipids from biological matrices like human plasma are based on liquid-liquid extraction (LLE). However, these methods are labor-intensive, time-consuming, and can show poor reproducibility and selectivity on lipid extraction. A novel, solid-phase extraction (SPE) approach was demonstrated to extract lipids from human plasma using a lipid extraction SPE in both cartridge and 96-well-plate formats, followed by analysis using a combination of targeted and untargeted liquid chromatography/mass spectrometry. The Lipid Extraction SPE method was compared to traditional LLE methods for lipid class recovery, lipidome coverage, and reproducibility. The novel SPE method used a simplified protocol with significant time and labor savings and provided equivalent or better qualitative and quantitative results than traditional LLE methods with respect to several critical performance metrics; recovery, reproducibility, and lipidome coverage.

Variability of Lipids in Human Milk

Lipids in breastmilk play a critical role in infant growth and development. However, few studies have investigated sources of variability of both high- and low-abundant milk lipids. The objective of our study was to investigate individual and morning-evening differences in the human milk lipidome. In this study, a modified two-phase method (MTBE: Methanol 7:2) was validated for the extraction of lipids from human breastmilk. This method was then applied to samples from a group of 20 healthy women to measure inter- and intra-individual (morning versus evening) variability of the breastmilk lipidome. We report here the levels of 237 lipid species from 13 sub-classes using reversed-phase liquid chromatography mass spectrometry (RP-LCMS) and direct-infusion mass spectrometry (DI-MS). About 85% of lipid species showed stable inter-individual differences across time points. Half of lipid species showed higher concentrations in the evening compared with the morning, with phosphatidylethanolamines (PEs) and triacylglycerols (TAGs) exhibiting the largest changes. In morning and evening samples, the biological variation was greater for diacylglycerols (DAGs) and TAGs compared with phospholipids and sphingolipids, and the variation in DAGs and TAGs was greater in evening samples compared with morning samples. These results demonstrate that variation in the milk lipidome is strongly influenced by individual differences and time of day.

Simple, Rapid Lipidomic Analysis of Triacylglycerols in Bovine Milk by Infusion-Electrospray Mass Spectrometry

Bovine milk is a complex mixture of lipids, proteins, carbohydrates, and other factors of which lipids comprise 3-5% of the total mass. Rapid analysis and characterization of the triacylglycerols (TAG) that comprise about 95% of the total lipid is daunting given the numerous TAG species. In the attached methods paper, we demonstrate an improved method for identifying and quantifying TAG species by infusion-based "shotgun" lipidomics. Because of the broad range of TAG species in milk, a single internal standard was insufficient for the analysis and required sectioning the spectrum into three portions based upon mass range to provide accurate quantitation of TAG species. Isobaric phospholipid interferences were removed using a simple dispersive solid-phase extraction step. Using this method, > 100 TAG species were quantitated by acyl carbon number and desaturation level in a sample of commercially purchased bovine milk.

Comprehensive Characterization of Bovine Milk Lipids: Triglycerides

A comprehensive survey on triglycerides (TAGs) of bovine milk was conducted by a combination of exhaustive liquid chromatography (LC) separation, high-resolution mass spectrometry (MS) detection, and automated lipid molecular feature extraction. A total of 220 groups (a series of species having the same chemical formula and mass) and 3454 molecular species of TAGs were identified based on the accurate mass of the parent ion as well as MS2 information. Sixty-five different fatty acids (FAs) were found across these TAG species; C4:0, C6:0, C8:0, C10:0, C12:0, C14:0, C16:0, C18:0, and C18:1 were the most frequent FAs, whereas C11:3, C11:4, C27:0, C27:1, C28:0, and C28:1 were rare FAs in TAG molecules. The number of species identified represents only a small portion of total TAG molecules that can be theoretically synthesized from 65 FAs. Each TAG group contains on average 15-16 isomeric species (species with different FA composition), but positional isomers do not seem to be widespread. As the isomeric species cannot be completely resolved chromatographically, quantification of TAG was conducted at the group level. The most abundant TAG groups in bovine milk include TAG 34:0, TAG 36:0, TAG 38:1, TAG 38:0, and TAG 40:1. This study provides the most comprehensive milk TAG inventory so far that can be used as a reference for studying milk lipids.

A Novel Lipidomics-Based Approach to Evaluating the Risk of Clinical Hepatotoxicity Potential of Drugs in 3D Human Microtissues

The importance of adsorption, distribution, metabolism, excretion, and toxicity (ADMET) analysis is expected to grow substantially due to recent failures in detecting severe toxicity issues of new chemical entities during preclinical/clinical development. Traditionally, safety risk assessment studies for humans have been conducted in animals during advanced preclinical or clinical phase of drug development. However, potential drug toxicity in humans now needs to be detected in the drug discovery process as soon as possible without reliance on animal studies. The "omics", such as genomics, proteomics, and metabolomics, have recently entered pharmaceutical research in both drug discovery and drug development, but to the best of our knowledge, no applications in high-throughput safety risk assessment have been attempted so far. This paper reports an innovative method to anticipate adverse drug effects in an early discovery phase based on lipid fingerprints using human three-dimensional microtissues. The risk of clinical hepatotoxicity potential was evaluated for a data set of 22 drugs belonging to five different therapeutic chemical classes and with various drug-induced liver injury effect. The treatment of microtissues with repeated doses of each drug allowed collecting lipid fingerprints for five time points (2, 4, 7, 9, and 11 days), and multivariate statistical analysis was applied to search for correlations with the hepatotoxic effect. The method allowed clustering of the drugs based on their hepatotoxic effect, and the observed lipid impairments for a number of drugs was confirmed by literature sources. Compared to traditional screening methods, here multiple interconnected variables (lipids) are measured simultaneously, providing a snapshot of the cellular status from the lipid perspective at a molecular level. Applied here to hepatotoxicity, the proposed workflow can be applied to several tissues, being tridimensional microtissues from various origins.

Simultaneous Analysis of Epoxidized and Hydroperoxidized Triacylglycerols in Canola Oil and Margarine by LC-MS

The progress of lipid oxidation in foods is evaluated by measuring the peroxides and their scission products. However, hydrogen abstraction-independent pathways are not considered by commonly applied methods despite the known reactivity of epoxides toward biomolecules. Herein, a novel liquid chromatography tandem-mass spectrometry method was developed to detect hydroperoxidized and epoxidized triacylglycerols (TAGs) without derivatization or hydrolyzation of food samples. Epoxidized TAGs could be detected in refined canola oil at concentrations of 96.8 ± 2.08 μM, while only 5.77 ± 0.04 μM hydroperoxidized TAGs could be determined. In contrast to canola oil, margarine was more resistant to lipid oxidation since generation of epoxidized TAGs could only be marginally enhanced from 21.7 ± 0.48 to 28.8 ± 0.64 μM in margarine after treatment at 180 °C for 60 min, as also reflected by a peroxide value of 0.80 ± 0.00 mequiv O₂/kg, which remained unchanged. The new method allows the assessment of food safety by the simultaneous measurement of hydroperoxidized and epoxidized TAGs without hydrolysis and laborious sample preparation.

Comparison of Single Phase and Biphasic Extraction Protocols for Lipidomic Studies Using Human Plasma

Lipidomic profiling of plasma is an emerging field, given the importance of lipids in major cellular pathways, and is dependent on efficient lipid extraction protocols. Recent attention has turned to plasma lipidomics as a means to identify potential diagnostic and prognostic biomarkers related to dementia, neuropsychiatric health and disease. Although several solvent-based lipid extraction protocols have been developed and are currently in use, novel and more efficient methods could greatly simplify lipid analysis in plasma and warrant investigation. Human plasma from normolipidemic adult volunteers was collected to evaluate three different solvent extraction protocols, including the classical Folch method, the methanol/tert-butyl methyl ether (MTBE) (Matyash) method, and a recent single-phase methanol/1-butanol (Alshehry) method. Extracted lipids were analyzed using liquid chromatography mass spectrometry (LC-MS) in positive and negative ion mode. Overall, more than 500 different lipids were identified in positive and negative ion mode combined. Our data show that the single phase Alshehry method was as effective as the Folch and Matyash methods in extracting most lipid classes and was more effective in extraction of polar lipids. Normalized peak areas of the Alshehry method were highly and positively correlated with both the Folch and Matyash methods (r 2 = 0.99 and 0.97, respectively). Within- and between- subject correlations were r = 0.99 and 0.96, respectively. Median intra-assay coefficient of variation (CV%) in positive mode was 14.1, 15.1, and 21.8 for the Alshehry, Folch and Matyash methods, respectively. Median Alshehry inter-assay CV (collected over 5 separate days) was 14.4%. In conclusion, the novel Alshehry method was at least as good as, if not better than the established biphasic extraction methods in detecting a wide range of lipid classes, using as little as 10 μL of plasma, and was highly reproducible, safer and more environmentally-friendly as it doesn't require chloroform.

Contemporary lipidomic analytics: opportunities and pitfalls

Recent advances in analytical techniques have greatly enhanced the depth of coverage, however lipidomic studies are still restricted to analysing only a subset of known lipids. Numerous complementary techniques are used for investigation of cellular lipidomes, including mass spectrometry (MS), nuclear magnetic resonance and vibrational spectroscopy. The development in electrospray ionization (ESI) MS has accelerated lipidomics research in the past two decades and represents one of the most widely used technique. The versatility of ESI-MS systems allows development of methods to detect and quantify a large diversity of lipid species and classes. However, highly targeted and specific approaches can preclude global analysis of many lipid classes. Indeed, experimental procedures are generally optimised for the lipid species, or lipid class of interest. Therefore, careful consideration of experimental procedures is required for characterisation of biological lipidomes. The current review will describe the lipidomic approaches for considering tissue lipid physiology. Discussion of the main sequences in a lipidomics workflow will be presented, including preparation of samples, accurate quantitation of lipid species and statistical modelling.

Comparison of methylation methods for fatty acid analysis of milk fat

Three acid- and alkaline-catalysed transesterification methods were compared with the aim to validate a simple yet reliable protocol for fatty acid (FA) profiling of milk fat. While both the acid- and alkaline-catalysed methods were able to convert completely triglycerides and phospholipids into fatty acid methyl esters (FAMEs), the acid catalyst caused significant degradation of conjugated linoleic acid C18:2c9t11 at high temperature. Although a milder temperature can mitigate this negative impact, a long reaction time (2 h) is required to achieve full methylation. By contrast, despite being unable to methylate free fatty acids (FFA), the alkaline-catalysed transesterification yielded comparable results for all major FA due to the very low level of FFA in milk. The alkaline-catalysed methylation is benign for C18:2c9t11. We recommend here a simple one-step protocol based on 0.2 M methanolic KOH, a short reaction time (20 min) and a mild reaction temperature (50 °C) for milk FAME preparation.

Heat Stress in Dairy Cattle Alters Lipid Composition of Milk

Heat stress, potentially affecting both the health of animals and the yield and composition of milk, occurs frequently in tropical, sub-tropical and temperate regions. A simulated acute heat stress experiment was conducted in controlled-climate chambers and milk samples collected before, during and after the heat challenge. Milk lipid composition, surveyed using LC-MS, showed significant changes in triacylglycerol (TAG) and polar lipid profiles. Heat stress (temperature-humidity index up to 84) was associated with a reduction in TAG groups containing short- and medium-chain fatty acids and a concomitant increase in those containing long-chain fatty acids. The abundance of five polar lipid classes including phosphatidylethanolamine, phosphatidylserine, phosphatidylcholine, lysophosphatidylcholine and glucosylceramide, was found to be significantly reduced during heat stress. Lysophosphatidylcholine, showing the greatest reduction in concentration, also displayed a differential response between heat tolerant and heat susceptible cows during heat stress. This phospholipid could be used as a heat stress biomarker for dairy cattle. Changes in TAG profile caused by heat stress are expected to modify the physical properties of milk fat, whereas the reduction of phospholipids may affect the nutritional value of milk. The results are discussed in relation to animal metabolism adaptation in the event of acute heat stress.