C18 Fatty Acids Research Articles

Effects of Different Shade Treatments on the Epidermal Wax Deposition of Hosta Genotypes with Different Glaucousness of Leaf Surface

Epidermal wax is strategically situated at the interface between plants and air; therefore, it plays a key role in plants’ interactions with their surroundings. It is also unstable and susceptible to light intensity. Hosta plants are shade-loving herbs with admirable flowers and leaves. Hosta ‘Halcyon’ and Hosta ensata F. Maek. are two species of Hosta with a glaucous and a glossy appearance, respectively. Light intensity can affect the composition of epicuticular wax on the leaf surface, which influences the leaf color phenotype and ornamental value. In this paper, the crystal micromorphology, content, and components of epicuticular wax on the leaves of two species of Hosta under different light conditions (10%-, 30%-, 50%-, 70%-, and 100%-intensity sunlight, relative light intensity (RLI)) have been studied using pot experiments. The results indicate that the epicuticular wax crystals of H. ‘Halcyon’ and H. ensata are tubular and platelet-like, respectively. The wax crystals of H. ‘Halcyon’ melted and formed a thick crust under 100% RLI, and those of H. ensata melted and formed a thick crust under 70% and 100% RLI conditions. The primary ingredients of the epicuticular wax of the two species of Hosta contained primary alcohols, alkanes, fatty acids, and esters; β-diketones were only detected in H. ‘Halcyon’. The quantity of epicuticular wax of H. ‘Halcyon’ reduced at first and then increased with an RLI increase, achieving its lowest value at 50% RLI, but that of H. ensata declined little by little. The amounts of C28 primary alcohols, C31 alkanes, and C18 fatty acids were significantly higher than those of other carbon atoms in the two genotypes of Hosta. The C31β-diketones content decreased with the increase in light intensity, which caused the white frost phenotype to gradually weaken in H. ‘Halcyon’.

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.

Effective complete replacement of fish oil by linseed oil in diets for thick-lipped grey mullet (Chelon labrosus) juveniles reared at three environmental salinities

One of the major challenges for fish oil replacement by alternative oils is the limited capacity of marine fish species to convert 18C fatty acids into long-chain poly unsaturated fatty acids (LC-PUFA). Since salinity markedly affects this conversion capacity, euryhaline species, such as thick-lipped grey mullet (Chelon labrosus), may have a good potential to use diets without inclusion of fish oil. To test this hypothesis, thick-lipped grey mullet juveniles were fed two different diets based on fish oil (FO diet) or linseed oil (LO diet) at three different salinities: 46 ppt, 35 ppt, and 16 ppt. At the end of the trial, the biochemical and fatty acid composition of whole-body, liver, and muscle, as well as the relative expression of the genes codifying for the elongase Elovl5 and the desaturase Fads2 in liver, were determined. The results showed the good capacity of mullet juveniles to convert 18C fatty acids into LC-PUFA, which was enhanced by the replacement of FO by LO and the reduction of salinity to an isosmotic level (16 ppt). Besides, these juveniles efficiently used diets with complete replacement of FO by LO with growth performance, body composition, and LC-PUFA fatty acid profiles similar to those of fish fed FO, particularly when reared at 16 ppt.

Proximate composition, fatty acid characteristics, amino acid profile and mineral content of fish Acanthurus sohal

The study's objective was to explore the chemical composition of Acanthurus sohal fish flesh and their nutritional quality. Fish samples were caught in the Red Sea, prepared, and analysed for proximate composition, fatty acid, amino acid and mineral content. The results revealed that fish flesh contained 71.1 % moisture, 20.7 % crude protein, 5 % crude lipids and 1.7 % ash. The fatty acids were dominant by 61.93 % saturated fatty acids. Palmitic was the most common (40.35 %) saturated fatty acids, while monounsaturated fatty acids and polyunsaturated fatty acids accounted for 22.59 % and 15.48 %, respectively. The fish fat consisted of appreciable amounts of odd-numbered fatty acids heptadecanoic and heptadecenoic acids standing for 1.62 % and 1.45 %, respectively. The fatty acids were predominated by C16, C18 and C20 fatty acids. The percentage of n-6/n-3 reached 2.26. Seventeen amino acids were identified in A. sohal flesh protein, eight of which were essential amino acids (EAAs); they amounted to 375.47 mg/g crude protein. Lysine was the most common EAA (64.49 mg/g crude protein). Aromatic amino acid and sulphur amino acid constituted 112.43 and 47.56 mg/g protein, respectively. The following macroelement concentration ranking was identified: Ca > P > K > Na > Mg, while the concentration of vital elements was Fe > Zn > Cu > Cr > I > Se > Co.

Bicarbonate concentration influences carbon utilization rates and biochemical profiles of freshwater and marine microalgae.

Selecting the optimal microalgal strain for carbon capture and biomass production is crucial for ensuring the commercial viability of microalgae-based biorefinery processes. This study aimed to evaluate the impact of varying bicarbonate concentrations on the growth rates, inorganic carbon (IC) utilization, and biochemical composition of three freshwater and two marine microalgal species. Parachlorella kessleri, Vischeria cf. stellata, and Porphyridium purpureum achieved the highest carbon removal efficiency (>85%) and biomass production at 6gL-1 sodium bicarbonate (NaHCO3), while Phaeodactylum tricornutum showed optimal performance at 1gL-1 NaHCO3. The growth and carbon removal rate of Scenedesmus quadricauda increased with increasing NaHCO3 concentrations, although its highest carbon removal efficiency (∼70%) was lower than the other species. Varying NaHCO3 levels significantly impacted the biochemical composition of P. kessleri, S. quadricauda, and P. purpureum but did not affect the composition of the remaining species. The fatty acid profiles of the microalgae were dominated by C16 and C18 fatty acids, with P. purpureum and P. tricornutum yielding relatively high polyunsaturated fatty acid content ranging between 14% and 30%. Furthermore, bicarbonate concentration had a species-specific effect on the fatty acid and chlorophyll-a content. This study demonstrates the potential of bicarbonate as an effective IC source for microalgal cultivation, highlighting its ability to select microalgal species for various applications based on their carbon capture efficiency and biochemical composition.

Effects of branched-chain amino acids on surfactin structure and antibacterial activity in Bacillus velezensis YA215.

Antibiotics are essential for combating pathogens; however, their misuse has led to increased resistance, necessitating the search for effective, low-toxicity alternatives. Surfactin, a cyclic lipopeptide with a C12-C17 β-hydroxy fatty acid chain, exhibits significant antibacterial activity and resists resistance, making it a research focus. Nonetheless, the effects of branched-chain amino acids (BCAAs) on surfactin's structure and activity are not well understood. This study examines the influence of BCAAs (L-valine, L-leucine, and L-isoleucine) on the lipopeptide (surfactin) produced by Bacillus velezensis YA215. Process optimization shows that adding 1g/L of L-Leu and L-Ile, and 0.5g/L of L-Val, maximized surfactin production to 18.59%, 19.23%, and 20.64%, respectively. Surfactin content peaked at 36h with L-Val and L-Ile, yielding 19.72% and 11.37%. In contrast, L-Leu addition peaked at 24h, yielding 11.33%. Notably, L-Val supplementation resulted in the highest relative surfactin content. Antimicrobial testing demonstrated that BCAAs significantly enhance the antibacterial effects of lipopeptides against Escherichia coli and Staphylococcus aureus, with Val showing the most pronounced effect. The addition of BCAAs notably altered the composition of surfactin fatty acid chains. Specifically, Val increased the proportions of iso C14 and iso C16 β-hydroxy fatty acids from 13.3% and 4.216-23.803% and 8.31%, respectively. Additionally, the amino acid composition at the 7th position of the peptide chain changed significantly, especially with Val addition, which increased the proportion of C14 [Val 7] surfactin by 3.29 times. These structural changes are likely associated with the enhanced antibacterial activity of surfactin. These findings provide valuable insights into the roles of BCAAs in microbial fermentation, underscoring their importance in metabolic engineering to enhance the production of bioactive compounds.

Drought and high heat stresses modify Brassica napus L. leaf cuticular wax

Brassica napus L. is dual-purpose oilseed crop for food, feed and biofuel. Breeding for cultivars adapted to environmental stresses, especially drought and high heat stresses, is one of the strategies that has the attention of breeders. To evaluate the effects of those stresses on leaf wax accumulations, a replicated growth chamber experiment was designed to include three factors: drought (D), high heat (H) and genotypes (G). Data showed significant variations in leaf wax accumulations in response to those three factors and their combinations. For example, the accumulation of the C24 primary alcohol wax was affected by heat, drought, genotype, DxH, HxG, DxG and DxHxG, while the accumulation of the C16 fatty acid wax was affected by drought only. The results indicated that brassica leaf wax accumulation rates under those stresses are genotype dependent and suggest choosing specific parent(s) is an important factor for breeding for those stress factors. The C28 fatty acid, C29 primary alcohol and C30 alkane waxes showed abundance on brassica leaves grown under combination of drought and heat stresses, suggesting them as potential candidates for improving the stress tolerance against those intense stressors. Combination of drought and heat showed to have synergetic effects on specific brassica leaf waxes indicating the possibility to breed for both drought and heat tolerances in Brassica napus at the same time.

Simplification of Dietary Treatment in Pharmacoresistant Epilepsy: Impact of C8 and C10 Fatty Acids on Sirtuins of Neuronal Cells In Vitro.

Pharmacotherapy is the therapeutic mainstay in epilepsy; however, in about 30% of patients, epileptic seizures are drug-resistant. A ketogenic diet (KD) is an alternative therapeutic option. The mechanisms underlying the anti-seizure effect of a KD are not fully understood. Epileptic seizures lead to an increased energy demand of neurons. An improvement in energy provisions may have a protective effect. C8 and C10 fatty acids have been previously shown to activate mitochondrial function in vitro. This could involve sirtuins (SIRTs) as regulatory elements of energy metabolism. The aim of the present study was to investigate whether ß-hydroxybutyrate (ßHB), C8 fatty acids, C10 fatty acids, or a combination of C8 and C10 (250/250 µM) fatty acids, which all increase under a KD, could up-regulate SIRT1, -3, -4, and -5 in HT22 hippocampal murine neurons in vitro. Cells were incubated for 1 week in the presence of these metabolites. The sirtuins were measured at the enzyme (fluorometrically), protein (Western blot), and gene expression (PCR) levels. In hippocampal cells, the C8, C10, and C8 and C10 incubations led to increases in the sirtuin levels, which were not inferior to a ßHB incubation as the 'gold standard'. This may indicate that both C8 and C10 fatty acids are important for the antiepileptic effect of a KD. A KD may be replaced by nutritional supplements of C8 and C10 fatty acids, which could facilitate the diet.

Biosynthesis of Polyhydroxyalkanoates in Cupriavidus necator B-10646 on Saturated Fatty Acids.

It has been established that the wild-type Cupriavidus necator B-10646 strain uses saturated fatty acids (SFAs) for growth and polyhydroxyalkanoate (PHA) synthesis. It uses lauric (12:0), myristic (14:0), palmitic (16:0) and stearic (18:0) acids as carbon sources; moreover, the elongation of the C-chain negatively affects the biomass and PHA yields. When bacteria grow on C12 and C14 fatty acids, the total biomass and PHA yields are comparable up to 7.5 g/L and 75%, respectively, which twice exceed the values that occur on longer C16 and C18 acids. Regardless of the type of SFAs, bacteria synthesize poly(3-hydroxybutyrate), which have a reduced crystallinity (Cx from 40 to 57%) and a molecular weight typical for poly(3-hydroxybutyrate) (P(3HB)) (Mw from 289 to 465 kDa), and obtained polymer samples demonstrate melting and degradation temperatures with a gap of about 100 °C. The ability of bacteria to assimilate SFAs opens up the possibility of attracting the synthesis of PHAs on complex fat-containing substrates, including waste.

Transcriptomic and lipidomic analysis of the differential pathway contribution to the incorporation of erucic acid to triacylglycerol during Pennycress seed maturation.

Thlaspi arvense (Pennycress) is an emerging feedstock for biofuel production because of its high seed oil content enriched in erucic acid. A transcriptomic and a lipidomic study were performed to analyze the dynamics of gene expression, glycerolipid content and acyl-group distribution during seed maturation. Genes involved in fatty acid biosynthesis were expressed at the early stages of seed maturation. Genes encoding enzymes of the Kennedy pathway like diacylglycerol acyltransferase1 (TaDGAT1), lysophosphatidic acid acyltransferase (TaLPAT) or glycerol 3-phosphate acyltransferase (TaGPAT) increased their expression with maturation, coinciding with the increase in triacylglycerol species containing 22:1. Positional analysis showed that the most abundant triacylglycerol species contained 18:2 at sn-2 position in all maturation stages, suggesting no specificity of the lysophosphatidic acid acyltransferase for very long chain fatty acids. Diacylglycerol acyltransferase2 (TaDGAT2) mRNA was more abundant at the initial maturation stages, coincident with the rapid incorporation of 22:1 to triacylglycerol, suggesting a coordination between Diacylglycerol acyltransferase enzymes for triacylglycerol biosynthesis. Genes encoding the phospholipid-diacylglycerol acyltransferase (TaPDAT1), lysophosphatidylcholine acyltransferase (TaLPCAT) or phosphatidylcholine diacylglycerolcholine phosphotransferase (TaPDCT), involved in acyl-editing or phosphatidyl-choline (PC)-derived diacylglycerol (DAG) biosynthesis showed also higher expression at the early maturation stages, coinciding with a higher proportion of triacylglycerol containing C18 fatty acids. These results suggested a higher contribution of these two pathways at the early stages of seed maturation. Lipidomic analysis of the content and acyl-group distribution of diacylglycerol and phosphatidyl-choline pools was compatible with the acyl content in triacylglycerol at the different maturation stages. Our data point to a model in which a strong temporal coordination between pathways and isoforms in each pathway, both at the expression and acyl-group incorporation, contribute to high erucic triacylglycerol accumulation in Pennycress.

The role of C18 fatty acids in improving the digestion and retrogradation properties of highland barley starch

In this study, five C18 fatty acids (FA) with different numbers of double bonds and configurations including stearic acid (SA), oleic acid (OA), elaidic acid (EA), linoleic acid (LA), and α-linolenic acid (ALA), were selected to prepare highland barely starch (HBS)-FA complexes to modulate digestibility and elaborate the underlying mechanism. The results showed that HBS-SA had the highest complex index (34.18 %), relative crystallinity (17.62 %) and single helix content (25.78 %). Furthermore, the HBS-C18 FA complexes were formed by EA (C18 FA with monounsaturated bonds) that had the highest R1047/1022 (1.0509) and lowest full width at half-maximum (FWHM, 20.85), suggesting good short-range ordered structure. Moreover, all C18 FAs could form two kinds of V-type complexes with HBS, which can be confirmed by the results of CLSM and DSC measurements, and all of them showed significantly lower digestibility. HBS-EA possessed the highest resistant starch content (20.17 %), while HBS-SA had the highest slowly digestible starch content (26.61 %). In addition, the inhibition of HBS retrogradation by fatty acid addition was further proven, where HBS-SA gel firmness (37.80 g) and aging enthalpy value were the lowest, indicating the most effective. Overall, compounding with fatty acids, especially SA, could be used as a novel way to make functional foods based on HBS.

Enhanced Scenedesmus obliquus Cultivation in Plastic-Type Flat Panel Photobioreactor for Biodiesel Production

A plastic-type flat panel photobioreactor (PTFPP) prototype was designed for microalgae cultivation as biodiesel feedstock. The growth, biomass, and lipid production of the oleaginous microalga Scenedesmus obliquus were optimized through the enhanced design and cultivation conditions in the PTFPP. The optimization conditions include cultivation of the microalga in a flat panel photobioreactor manufactured from a 10 µm-thick plastic sheet with dimensions of 40 cm in width and 60 cm in height. The width of the designed plastic bags was adjusted by “4 ports” of circular adhesion points which make the volumetric cultural capacity 5 L. Cultivation of the microalga was optimized through the replacement of the sodium nitrate of the BBM medium with urea as a nitrogen source. Cultivation bags were subjected to continuous illumination with 3000 lux white, fluorescent lamps and aerated with 1.5 L air/min (equal to 0.3 VVM). Biomass production from the designed PTFPP reached 3 g/L with around 40% lipid content (on a dry weight basis). Based on a GC-MS analysis of the produced fatty acid methyl ester (biodiesel) from S. obliquus, the percentage of C16 and C18 fatty acids reached more than 90% of the defined fatty acids. Out of this percentage, 66.6% were unsaturated fatty acids. The produced fatty acid profile of the S. obliquus biomass cultivated in the designed PTFPP prototype could be considered a suitable feedstock for biodiesel production.

Effect of organic carbon sources on growth, lipid production and fatty acid profile in mixotrophic culture of Scenedesmus dimorphus (Turpin) Kützing

Due to non-renewability of fossil fuels and various environmental problems associated with their use, there is a growing interest in producing biodiesel from microalgae. Finding novel microalgal strains with desired characteristics such as rapid growth rates, high lipid productivity, and suitable fatty acid compositions is important for the production of biodiesel. Comparatively, photoautotrophic cultivation of microalgae results in low biomass yields and lipid productivities. Mixotrophic and heterotrophic cultures, in contrast, lead to higher biomass and lipid productivities but their productivities are species specific and depend a lot on the organic carbon source and culture conditions. In the present study, the potential of Scenedesmus dimorphus for biodiesel oil production under mixotrophic culture was investigated. The effects of organic carbon sources (glucose, ethanol and glycerol) on growth, biomass yields, lipid contents, lipid productivities and fatty acids compositions of Scenedesmus dimorphus in mixotrophic cultures were investigated. In comparison to photoautotrophic cultures, mixotrophic cultures produced significantly higher biomass concentration, lipid content, and lipid productivities (P≤0.05) under all the cultivation conditions investigated. The maximum biomass and lipid productivities achieved by mixotrophic culture were 83.88±0.05 and 17.11±0.04 mg L−1 day−1 respectively which are more than 2.6 and 3.1 folds higher than those obtained under photoautotrophic condition. Using glucose as the organic carbon source was better than ethanol and glycerol in terms of biomass and lipid productivities (glucose > ethanol > glycerol). The majority of the produced fatty acids were composed of C16 and C18 fatty acids. The two most abundant fatty acids in all the cultures were linolenic and palmitic acids. The values of biodiesel properties of oil obtained from S. dimorphus are within the American (ASTM D6751) and European (EN 14214) biodiesel specifications. The results show that S. dimorphus has good potentials for biodiesel oil production and that the productivity can be enhanced by mixotrophic cultivation.

Assimilation of fish farm wastes by the ecosystem engineering bivalve Atrina zelandica

As feed-additive aquaculture expands to open ocean areas, there is concern that ecologically important habitats may be adversely impacted by sedimentation of farm wastes. In this study, we investigated assimilation of salmon faecal wastes by an ecosystem engineering bivalve that occurs in open ocean environments (Atrina zelandica), as well as effects on physiology and fatty acid metabolism. A. zelandica were subjected to one of 3 treatment diets (fish faeces, 1:1 mix of algae:faeces and algae) in a 51 d laboratory trial. We found a diet-related response in fatty acid composition, including increased prevalence of oleic acid (OA) in digestive tissues of A. zelandica fed on both the fish faeces diet and the mixed diet, indicating fish wastes were assimilated in both treatments. Fish waste consumption was related to a more marked reduction in fatty acid content of digestive gland, as well as lower proportions of long-chain polyunsaturated fatty acids (LC-PUFA) in digestive tissues. Fatty acid composition in gonad and muscle tissues was more strongly influenced by sex. Regardless of dietary treatment, females accumulated C18 fatty acids in gonad tissues, particularly OA, which may preclude the use of OA as a fish waste tracer in this organ. The accumulation of specific fatty acids according to sex may indicate a capacity for preferential selection and retention or biosynthesis of biologically important fatty acids. If present, these mechanisms may increase resilience of A. zelandica to stress from deficiencies in LC-PUFA when using fish wastes as a trophic subsidy.

The Molecular Profile of Soil Microbial Communities Inhabiting a Cambrian Host Rock.

The process of soil genesis unfolds as pioneering microbial communities colonize mineral substrates, enriching them with biomolecules released from bedrock. The resultant intricate surface units emerge from a complex interplay among microbiota and plant communities. Under these conditions, host rocks undergo initial weathering through microbial activity, rendering them far from pristine and challenging the quest for biomarkers in ancient sedimentary rocks. In addressing this challenge, a comprehensive analysis utilizing Gas Chromatography Mass Spectrometry (GC-MS) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) was conducted on a 520-Ma-old Cambrian rock. This investigation revealed a diverse molecular assemblage with comprising alkanols, sterols, fatty acids, glycerolipids, wax esters, and nitrogen-bearing compounds. Notably, elevated levels of bacterial C16, C18 and C14 fatty acids, iso and anteiso methyl-branched fatty acids, as well as fungal sterols, long-chained fatty acids, and alcohols, consistently align with a consortium of bacteria and fungi accessing complex organic matter within a soil-type ecosystem. The prominence of bacterial and fungal lipids alongside maturity indicators denotes derivation from heterotrophic activity rather than ancient preservation or marine sources. Moreover, the identification of long-chain (>C22) n-alkanols, even-carbon-numbered long chain (>C20) fatty acids, and campesterol, as well as stigmastanol, provides confirmation of plant residue inputs. Furthermore, findings highlight the ability of contemporary soil microbiota to inhabit rocky substrates actively, requiring strict contamination controls when evaluating ancient molecular biosignatures or extraterrestrial materials collected.

Characterization of Three Types of Elongases from Different Fungi and Site-Directed Mutagenesis.

Fatty acid elongases play crucial roles in synthesizing long-chain polyunsaturated fatty acids. Identifying more efficient elongases is essential for enhancing oleaginous microorganisms to produce high yields of target products. We characterized three elongases that were identified with distinct specificities: McELO from Mucor circinelloides, PrELO from Phytophthora ramorum, and PsELO from Phytophthora sojae. Heterologous expression in Saccharomyces cerevisiae showed that McELO preferentially elongates C16 to C18 fatty acids, PrELO targets Δ6 polyunsaturated fatty acids, and PsELO uses long chain saturated fatty acids as substrates. McELO and PrELO exhibited more homology, potentially enabling fatty acid composition remodeling and enhanced LC-PUFAs production in oleaginous microorganisms. Site-directed mutagenesis of conserved amino acids across elongase types identified residues essential for activity, supported by molecular docking. Alanine substitution of conserved polar residues led to enzyme inactivation, underscoring their importance in the condensation reaction. Our findings offer promising elongase candidates for polyunsaturated fatty acid production, contributing to the bioindustry's sustainable development.

Exploring engineering strategies that enhance de novo production of exotic cyclopropane fatty acids in Saccharomyces cerevisiae.

Cycloalkanes have broad applications as specialty fuels, lubricants, and pharmaceuticals but are not currently available from renewable sources, whereas, production of microbial cycloalkanes such as cyclopropane fatty acids (CFA) has bottlenecks. Here, a systematic investigation was undertaken into the biosynthesis of CFA in Saccharomyces cerevisiae heterologously expressing bacterial CFA synthase. The enzyme catalyzes formation of a 3-membered ring in unsaturated fatty acids. Monounsaturated fatty acids in phospholipids (PL) are the site of CFA synthesis; precursor cis-Δ9 C16 and C18 fatty acids were enhanced through OLE1 and SAM2 overexpression which enhanced CFA in PL. CFA turnover from PL to storage in triacylglycerols (TAG) was achieved by phospholipase PBL2 overexpression and acyl-CoA synthase to increase flux to TAG. Consequently, CFA storage as TAG reached 12mgg-1 DCW, improved 3-fold over the base strain and >22% of TAG was CFA. Our research improves understanding of cycloalkane biosynthesis in yeast and offers insights into processing of other exotic fatty acids.

CO2 to green fuel converter: Photoautotrophic-cultivation of microalgae and its lipids conversion to biodiesel

This research focused on utilizing photoautotrophically-cultivated microalgae as efficient converters of CO2 into high-quality renewable biodiesel. This study investigated the feasibility of capturing CO2 from the atmosphere (0.04 % CO2) and simulating industrial sources (20–40 % CO2) for utilization as a simulated waste carbon source for the growth and biodiesel feedstock accumulation of three photoautotrophically-cultivated microalgae species, including Chlorella sp. AARL G049, Tetradesmus obliquus AARL G090, and Desmodesmus opoliensis AARL G085. The results demonstrated that all the tested microalgae are promising CO2-to-fuel converters due to their ability to efficiently convert CO2 into lipid-rich biomass, which can subsequently be processed into biodiesel. All three strains of microalgae displayed remarkable CO2 capture capabilities as well as significant biomass production and lipid accumulation, with the highest performance observed under a 20 % CO2 concentration. The microalgae demonstrated CO2 fixation rates ranging from 0.020 to 0.072 g-CO2/L/day, leading to significant improvements in both biomass productivity, which ranged from 0.011 to 0.040 g/L/day, and lipid accumulation, which ranged from 0.22 to 3.39 mg/L/day. Additionally, the lipid content varied between 5.04 % and 14.75 %. Interestingly, changes in CO2 concentration, ranging from 0.04 % to 40 %, significantly influenced the composition of fatty acids, leading to elevated levels of C16–C18 fatty acids. Nevertheless, these alterations had a minimal impact on the overall quality of biodiesel. The estimated fuel characteristics of the produced biodiesel complied with global specifications for biodiesel, providing better oxidative stability (≥6 h), high heating value (≥39 MJ/kg), and cetane number (≥47). Therefore, this study emphasizes sustainable CO2 capture and the potential of microalgae as a renewable source of economically viable biodiesel.

Engineering Yarrowia lipolytica for sustainable ricinoleic acid production: A pathway to free fatty acid synthesis

Ricinoleic acid (C18:1-OH, RA) is a valuable hydroxy fatty acid with versatile applications. The current industrial source of RA relies on the hydrolysis of castor bean oil. However, the coexistence of the toxic compound ricin and the unstable supply of this plant have led to an exploration of promising alternatives: generating RA in heterologous plants or microorganisms. In this study, we engineered the oleaginous yeast Yarrowia lipolytica to produce RA in the form of free fatty acids (FFA). First, we overexpressed fungal Δ12 oleate hydroxylase gene (CpFAH12) from Claviceps purpurea while deleting genes related to fatty acid degradation (MEF1 and PEX10) and oleic acid desaturation (FAD2). Since Δ12 oleate hydroxylase converts oleic acid (C18:1) located at the sn-2 position of phosphatidylcholine (PC), we next focused on increasing the PC pool containing oleic acid. This objective was achieved thorough implementing metabolic engineering strategies designed to enhance the biosynthesis of PC and C18 fatty acids. To increase the PC pool, we redirected the flux towards phospholipid biosynthesis by deleting phosphatidic acid phosphatase genes (PAH1 and APP1) and diacylglycerol acyltransferase gene (DGA1), involved in the production of diacylglycerol and triacylglycerol, respectively. Furthermore, the PC biosynthesis via the CDP-DAG pathway was enhanced through the overexpression of CDS1, PSD1, CHO2, and OPI3 genes. Subsequently, to increase the oleic acid content within PC, we overexpressed the heterologous fatty acid elongase gene (MaC16E) involved in the conversion of C16 to C18 fatty acids. As RA production titer escalated, the produced RA was mainly found in the FFA form, leading to cell growth inhibition. The growth inhibition was mitigated by inducing RA secretion via Triton X-100 treatment, a process that simultaneously amplified RA production by redirecting flux towards RA synthesis. The final engineered strain JHYL-R146 produced 2.061 g/L of free RA in a medium treated with 5% Triton X-100, constituting 74% of the total FFAs produced. Generating free RA offers the added benefit of bypassing the hydrolysis stage required when employing castor bean oil as an RA source. This achievement represents the highest level of RA synthesis from glucose reported thus far, underscoring the potential of Y. lipolytica as a host for sustainable RA production.

Oleic Acid Metabolism in Response to Glucose in C. elegans.

A key response to glucose stress is an increased production of unsaturated fatty acids to balance the increase in saturated fatty acids in the membrane. The C. elegans homolog of stearoyl-CoA desaturase, FAT-7, introduces the first double bond into saturated C18 fatty acids yielding oleic acid, and is a critical regulatory point for surviving cold and glucose stress. Here, we incorporated 13C stable isotopes into the diet of nematodes and quantified the 13C-labelled fatty acid using GC-MS and HPLC/MS-MS to track its metabolic response to various concentrations of glucose. Previous work has analyzed the membrane composition of C. elegans when responding to mild glucose stress and showed few alterations in the overall fatty acid composition in the membrane. Here, in nematodes exposed to higher concentrations of glucose, a specific reduction in oleic acid and linoleic acid was observed. Using time courses and stable isotope tracing, the response of fatty acid metabolism to increasing levels of glucose stress is characterized, revealing the funneling of monounsaturated fatty acids to preserve the abundance of polyunsaturated fatty acids. Taken together, higher levels of glucose unveil a specific reduction in oleic and linolenic acid in the metabolic rewiring required to survive glucose stress.