A gas chromatography full scan high resolution Orbitrap mass spectrometry method for separation and characterization of 3-hydroxymethyl pyridine ester of fatty acids at low levels

Rhamnolipids and fengycins interact differently with biomimetic lipid membrane models of Botrytis cinerea and Sclerotinia sclerotiorum: Lipidomics profiles and biophysical studies

Rhamnolipids (RLs) and Fengycins (FGs) are biosurfactants with very promising antifungal properties proposed to reduce the use of synthetic pesticides in crops. They are amphiphilic molecules, both known to target the plasma membrane. They act differently on Botrytis cinerea and Sclerotinia sclerotiorum, two close Sclerotiniaceae phytopathogenic fungi. RLs are more efficient at permeabilizing S. sclerotiorum, and FGs are more efficient at permeabilizing B. cinerea mycelial cells. To study the link between the lipid membrane composition and the activity of RLs and FGs, we analyzed the lipid profiles of B. cinerea and S. sclerotiorum. We determined that unsaturated or saturated C18 and saturated C16 fatty acids are predominant in both fungi. We also showed that phosphatidylethanolamine (PE), phosphatidic acid (PA), and phosphatidylcholine (PC) are the main phospholipids (in this order) in both fungi, with more PA and less PC in S. sclerotiorum. The results were used to build biomimetic lipid membrane models of B. cinerea and S. sclerotiorum for all-atom molecular dynamic simulations and solid-state NMR experiments to more deeply study the interactions between RLs or FGs with different compositions of lipid bilayers. Distinctive effects are exerted by both compounds. RLs completely insert in all the studied model membranes with a fluidification effect. FGs tend to form aggregates out of the bilayer and insert individually more easily into the models representative of B. cinerea than those of S. sclerotiorum, with a higher fluidification effect. These results provide new insights into the lipid composition of closely related fungi and its impact on the mode of action of very promising membranotropic antifungal molecules for agricultural applications.

Lifespan prolonging mechanisms and insulin upregulation without fat accumulation in long-lived reproductives of a higher termite

Kings and queens of eusocial termites can live for decades, while queens sustain a nearly maximal fertility. To investigate the molecular mechanisms underlying their long lifespan, we carried out transcriptomics, lipidomics and metabolomics in Macrotermes natalensis on sterile short-lived workers, long-lived kings and five stages spanning twenty years of adult queen maturation. Reproductives share gene expression differences from workers in agreement with a reduction of several aging-related processes, involving upregulation of DNA damage repair and mitochondrial functions. Anti-oxidant gene expression is downregulated, while peroxidability of membranes in queens decreases. Against expectations, we observed an upregulated gene expression in fat bodies of reproductives of several components of the IIS pathway, including an insulin-like peptide, Ilp9. This pattern does not lead to deleterious fat storage in physogastric queens, while simple sugars dominate in their hemolymph and large amounts of resources are allocated towards oogenesis. Our findings support the notion that all processes causing aging need to be addressed simultaneously in order to prevent it.

Advances in high resolution GC-MS technology: a focus on the application of GC-Orbitrap-MS in metabolomics and exposomics for FAIR practices

Gas chromatography-mass spectrometry (GC-MS) provides a complementary analytical platform for capturing volatiles, non-polar and (derivatized) polar metabolites and exposures from a diverse array of matrixes. High resolution (HR) GC-MS as a data generation platform can capture data on analytes that are usually not detectable/quantifiable in liquid chromatography mass-spectrometry-based solutions. With the rise of high-resolution accurate mass (HRAM) GC-MS systems such as GC-Orbitrap-MS in the last decade after the time-of-flight (ToF) renaissance, numerous applications have been found in the fields of metabolomics and exposomics. In a short span of time, a multitude of studies have used GC-Orbitrap-MS to generate exciting new high throughput data spanning from diverse basic to applied research areas. The GC-Orbitrap-MS has found application in both targeted and untargeted efforts for capturing metabolomes and exposomes across diverse studies. In this review, I capture and summarize all the reported studies to date, and provide a snapshot of the milieu of commercial and open-source software solutions, spectral libraries, and informatics solutions available to a GC-Orbitrap-MS system instrument user or a data analyst dealing with these datasets. Lastly, but importantly, I provide an account on data sharing and meta-data capturing solutions that are available to make HRAM GC-MS based metabolomics and exposomics studies findable, accessible, interoperable, and reproducible (FAIR). These FAIR practices would allow data generators and users of GC-HRMS instruments to help the community of GC-MS researchers to collaborate and co-develop exciting tools and algorithms in the future.

Production of 10-methyl branched fatty acids in yeast

BACKGROUND

Despite the environmental value of biobased lubricants, they account for less than 2% of global lubricant use due to poor thermo-oxidative stability arising from the presence of unsaturated double bonds. Methyl branched fatty acids (BFAs), particularly those with branching near the acyl-chain mid-point, are a high-performance alternative to existing vegetable oils because of their low melting temperature and full saturation.

RESULTS

We cloned and characterized two pathways to produce 10-methyl BFAs isolated from actinomycetes and γ-proteobacteria. In the two-step bfa pathway of actinomycetes, BfaB methylates Δ9 unsaturated fatty acids to form 10-methylene BFAs, and subsequently, BfaA reduces the double bond to produce a fully saturated 10-methyl branched fatty acid. A BfaA-B fusion enzyme increased the conversion efficiency of 10-methyl BFAs. The ten-methyl palmitate production (tmp) pathway of γ-proteobacteria produces a 10-methylene intermediate, but the TmpA putative reductase was not active in E. coli or yeast. Comparison of BfaB and TmpB activities revealed a range of substrate specificities from C14-C20 fatty acids unsaturated at the Δ9, Δ10 or Δ11 position. We demonstrated efficient production of 10-methylene and 10-methyl BFAs in S. cerevisiae by secretion of free fatty acids and in Y. lipolytica as triacylglycerides, which accumulated to levels more than 35% of total cellular fatty acids.

CONCLUSIONS

We report here the characterization of a set of enzymes that can produce position-specific methylene and methyl branched fatty acids. Yeast expression of bfa enzymes can provide a platform for the large-scale production of branched fatty acids suitable for industrial and consumer applications.

Structure determination of conjugated linoleic and linolenic acids

Conjugated linoleic and linolenic acids (CLA and CLnA) can be found in dairy, ruminant meat and oilseeds, these types of unsaturated fatty acids consist of various positional and geometrical isomers, and have demonstrated health-promoting potential for human beings. Extensive reviews have reported the physiological effects of CLA, CLnA, while little is known regarding their isomer-specific effects. However, the isomers are difficult to identify, owing to (i) the similar retention time in common chromatographic methods; and (ii) the isomers are highly sensitive to high temperature, pH changes, and oxidation. The uncertainties in molecular structure have hindered investigations on the physiological effects of CLA and CLnA. Therefore, this review presents a summary of the currently available technologies for the structural determination of CLA and CLnA, including the presence confirmation, double bond position determination, and the potential stereo-isomer determination. Special focus has been projected to the novel techniques for structure determination of CLA and CLnA. Some possible future directions are also proposed.

Fermentation process for producing CFAs using Yarrowia lipolytica

Past research has sought to improve the production of cyclopropane fatty acids by the oleaginous yeast Yarrowia lipolytica by heterologously expressing the E. coli fatty acid synthase gene and improving cultivation processes. Cyclopropane fatty acids display properties that hold promise for biofuel applications. The E. coli fatty acid synthase gene was introduced into several genetic backgrounds of the yeast Y. lipolytica to optimize lipid synthesis; the mean cyclopropane fatty acid productivity was 43 mg L-1 h-1 on glucose, and the production rate reached its maximum (3.06 g L-1) after 72 h of cultivation in a bioreactor. The best strain (JMY6851) overexpressed simultaneously the E. coli cyclopropane fatty acid synthase gene under a hybrid promoter (hp8d) and Y. lipolytica LRO1 gene. In fed-batch process using crude glycerol as carbon source, JMY6851 strain displayed high lipid accumulation (78% of dry cell weight) and high biomass production (56 g L-1). After 165 h of cultivation, cyclopropane fatty acids represented 22% of the lipids produced; cyclopropane fatty acid productivity (103.3 mg L-1 h-1) was maximal at 72.5 h of cultivation.

Evaluation of performance and validity limits of gas chromatography electron ionisation with Orbitrap detection for fatty acid methyl ester analyses

RATIONALE

While the GC-Orbitrap, marketed in 2015, represents a technological breakthrough in terms of sensitivity, resolution and mass stability, many studies have reported ion ratio modification in mass spectra using the standard 70 eV electron ionisation.

METHODS

We studied the influence of the acquisition and sample parameters leading to these modifications on fatty acid methyl esters (FAMEs).

RESULTS

FAMEs showed that these variations in relative intensities of ions were related to the acquisition parameters such as the mass range and the offset values of the C-TRAP, but also directly related to the column concentration of the sample, and especially that it was molecule-dependent. Advantageously, it is possible to use this feature to promote the molecular ions of FAMEs sometimes not present in a spectrum under electron ionisation at 70 eV.

CONCLUSIONS

The 70 eV electron ionisation mass spectra from the GC-Orbitrap were clearly molecule-dependent and could be due to metastable ions during storage states in the C-TRAP.

Optimization of cyclopropane fatty acids production in Yarrowia lipolytica

Cyclopropane fatty acids, which can be simply converted to methylated fatty acids, are good unusual fatty acid candidates for long-term resistance to oxidization and low-temperature fluidity useful for oleochemistry and biofuels. Cyclopropane fatty acids are present in low amounts in plants or bacteria. In order to develop a process for large-scale biolipid production, we expressed 10 cyclopropane fatty acid synthases from various organisms in the oleaginous yeast Yarrowia lipolytica, a model yeast for lipid metabolism and naturally capable of producing large amounts of lipids. The Escherichia coli cyclopropane fatty acid synthase expression in Y. lipolytica allows the production of two classes of cyclopropane fatty acids, a C17:0 cyclopropanated form and a C19:0 cyclopropanated form, whereas others produce only the C17:0 form. Expression optimization and fed-batch fermentation set-up enable us to reach a specific productivity of 0.032 g·L^-1 ·hr^-1 with a genetically modified strain containing cyclopropane fatty acid up to 45% of the total lipid content corresponding to a titre of 2.3 ± 0.2 g/L and a yield of 56.2 ± 4.4 mg/g.