Regulation of the Docosapentaenoic Acid/Docosahexaenoic Acid Ratio (DPA/DHA Ratio) in Schizochytrium limacinum B4D1

Accumulation of docosapentaenoic acid (n-3 DPA) in a novel isolate of the marine ichthyosporean Sphaeroforma arctica

OBJECTIVE

Currently, there is lack of a consistent and highly enriched source for docosapentaenoic acid (n-3 DPA, C22:5), and this work report the isolation of microorganism that naturally produces n-3 DPA.

RESULTS

In this work, we screened microorganisms in our culture collections with the goal to isolate a strain with high levels of n-3 DPA. We isolated a strain of Sphaeroforma arctica that produces up to 11% n-3 DPA in total fatty acid and has a high n-3 DPA to DHA/EPA ratio. The cell growth of the isolated strain was characterized using microscopy imaging and flow cytometer technologies to confirm the coenocytic pattern of cell divisions previously described in S. arctica. Our novel isolate of S. arctica grew more robustly and produced significantly more n-3 DPA compared to previously isolated and described strains indicating the uniqueness of the discovered strain.

CONCLUSION

Overall, this work reports a first isolate n-3 DPA producing microorganism and establishes the foundation for future strain improvement and elucidation of the physiological function of this LC-PUFA for human nutrition and health.

Enhancing the accumulation of lipid and docosahexaenoic acid in Schizochytrium sp. by co-overexpression of phosphopantetheinyl transferase and ω-3 fatty acid desaturase

Docosahexaenoic acid (DHA) as one of ω-3 polyunsaturated fatty acids (PUFAs), plays a key role in brain development, and is widely used in food additives and the pharmaceutical industry. Schizochytrium sp. is often considered as a satisfactory strain for DHA industrialization. The aim of this study was to assess the feasibility of phosphopantetheinyl transferase (PPTase) and ω-3 fatty acid desaturase (FAD) for regulating DHA content in Schizochytrium sp. PPTase is essential to activate the polyketide-like synthase (PKS) pathway, which can transfer apo-acyl-carrier protein (apo-ACP) into holo-ACP, and plays a key role in DHA synthesis. Moreover, DHA and docosapentaenoic acid (DPA) are synthesized by the PKS pathway simultaneously, so high DPA synthesis limits the increase of DHA content. In addition, the detailed mechanisms of PKS pathway have not been fully elucidated, so it is difficult to improve DHA content by modifying PKS. However, ω-3 FAD can convert DPA into DHA, and it is the most direct and effective way to increase DHA content and reduce DPA content. Based on this, PPTase was overexpressed to enhance the synthesis of DHA by the PKS pathway, overexpressed ω-3 FAD to convert the co-product of the PKS pathway into DHA, and co-overexpressed PPTase and ω-3 FAD. With these strategies, compared with wild type, the final lipid, and DHA titer were 92.5 and 51.5 g L-1 , which increased by 46.4% and 78.1%, respectively. This study established an efficient DHA production strain, and provided some feasible strategies for industrial DHA production in Schizochytrium sp.

Development of Schizochytrium sp. strain HS01 with high-DHA and low-saturated fatty acids production by multi-pronged adaptive evolution

PURPOSE

Docosahexaenoic acid (DHA) is an important omega-3 unsaturated fatty acid and has been widely applied in medicine, food additives, and feed ingredients. The fermentative production of DHA using microorganisms, including Schizochytrium sp., attracted much attention due to its high production efficiency and environment friendly properties. An efficient laboratory evolution approach was used to improve the strain's performance in this study.

METHODS

A multi-pronged laboratory evolution approach was applied to evolve high-yield DHA-producing Schizochytrium strain. We further employed comparative transcriptional analysis to identify transcriptional changes between the screened strain HS01 and its parent strain GS00.

RESULTS

After multiple generations of ALE, a strain HS01 with higher DHA content and lower saturated fatty acids content was obtained. Low nitrogen conditions were important for enhancing DHA biosynthesis in HS01. The comparative transcriptional analysis results indicated that during the fermentation process of HS01, the expression of key enzymes in the glycolysis, the pentose phosphate pathway and the tricarboxylic acid cycle were up-regulated, while the expression of polyketide synthase genes and fatty acid synthesis genes were similar to those in GS00.

CONCLUSION

The results suggest that the improved DHA production capacity of HS01 is not due to enhancement of the DHA biosynthesis pathway, but rather related to modulation of central metabolism pathways.

Deciphering and engineering the polyunsaturated fatty acid synthase pathway from eukaryotic microorganisms

Polyunsaturated fatty acids (PUFAs) are important nutrients that play important roles in human health. In eukaryotes, PUFAs can be de novo synthesized through two independent biosynthetic pathways: the desaturase/elongase pathway and the PUFA synthase pathway. Among them, PUFAs synthesized through the PUFA synthase pathway typically have few byproducts and require fewer reduction equivalents. In the past 2 decades, numerous studies have been carried out to identify, analyze and engineer PUFA synthases from eukaryotes. These studies showed both similarities and differences between the eukaryotic PUFA synthase pathways and those well studied in prokaryotes. For example, eukaryotic PUFA synthases contain the same domain types as those in prokaryotic PUFA synthases, but the number and arrangement of several domains are different; the basic functions of same-type domains are similar, but the properties and catalytic activities of these domains are somewhat different. To further utilize the PUFA synthase pathway in microbial cell factories and improve the productivity of PUFAs, many challenges still need to be addressed, such as incompletely elucidated PUFA synthesis mechanisms and the difficult genetic manipulation of eukaryotic hosts. In this review, we provide an updated introduction to the eukaryotic PUFA synthase pathway, summarize the functions of domains and propose the possible mechanisms of the PUFA synthesis process, and then provide future research directions to further elucidate and engineer the eukaryotic PUFA synthase pathway for the maximal benefits of humans.

Genetic regulation and fermentation strategy for squalene production in Schizochytrium sp

Squalene, as an important terpenoid, is extensively used in the medicine and health care fields owing to its functions of anti-oxidation, blood lipid regulation and cancer prevention. The marine microalgae, Schizochytrium sp., which acts as an excellent strain with potential of high squalene production was selected as the starting strain. The overexpressed strain with sqs gene got the reduced biomass and lipid, while the squalene titer was increased by 79.6% ± 4.7% to 12.8 ± 0.2 mg/L. In order to further increase squalene production, the recombinant strain (HS strain) with sqs and hmgr gene co-overexpression was further constructed. The biomass and squalene titer of the HS strain were increased by 13.6% ± 1.2% and 88.8% ± 5.3%, respectively, which indicated the carbon flux of the mevalonate pathway was enhanced for squalene accumulation. Regarding the squalene synthesis is completely coupled with cell growth, fermentation strategy to prolong the logarithmic growth phase was conducive to improve squalene production. Under the condition of optimal composition and concentrated medium, the squalene titer of HS strain was 27.0 ± 1.3 mg/L, which was 2.0 times that of the basal medium condition (13.5 ± 0.4 mg/L). This study which combined the metabolic engineering and fermentation strategy provides a new strategy for squalene production in Schizochytrium sp. KEY POINTS: •The overexpression of sqs and hmgr genes promoted carbon metabolism for squalene. •The optimal and concentrated media can increase squalene yield.

Overexpression of Two New Acyl-CoA:Diacylglycerol Acyltransferase 2-Like Acyl-CoA:Sterol Acyltransferases Enhanced Squalene Accumulation in Aurantiochytrium limacinum

Thraustochytrids are heterotrophic marine eukaryotes known to accumulate large amounts of triacylglycerols, and they also synthesize terpenoids like carotenoids and squalene, which all have an increasing market demand. However, a more extensive knowledge of the lipid metabolism is needed to develop thraustochytrids for profitable biomanufacturing. In this study, two putative type-2 Acyl-CoA:diacylglycerol acyltransferases (DGAT2) genes of Aurantiochytrium sp. T66, T66ASATa, and T66ASATb, and their homologs in Aurantiochytrium limacinum SR21, AlASATa and AlASATb, were characterized. In A. limacinum SR21, genomic knockout of AlASATb reduced the amount of the steryl esters of palmitic acid, SE (16:0), and docosahexaenoic acid, SE (22:6). The double mutant of AlASATa and AlASATb produced even less of these steryl esters. The expression and overexpression of T66ASATb and AlASATb, respectively, enhanced SE (16:0) and SE (22:6) production more significantly than those of T66ASATa and AlASATa. In contrast, these mutations did not significantly change the level of triacylglycerols or other lipid classes. The results suggest that the four genes encoded proteins possessing acyl-CoA:sterol acyltransferase (ASAT) activity synthesizing both SE (16:0) and SE (22:6), but with the contribution from AlASATb and T66ASATb being more important than that of AlASATa and T66ASATa. Furthermore, the expression and overexpression of T66ASATb and AlASATb enhanced squalene accumulation in SR21 by up to 88%. The discovery highlights the functional diversity of DGAT2-like proteins and provides valuable information on steryl ester and squalene synthesis in thraustochytrids, paving the way to enhance squalene production through metabolic engineering.

A 13CO2 Enrichment Experiment to Study the Synthesis Pathways of Polyunsaturated Fatty Acids of the Haptophyte Tisochrysis lutea

The production of polyunsaturated fatty acids (PUFA) in Tisochrysis lutea was studied using the gradual incorporation of a ¹³C-enriched isotopic marker, ¹³CO₂, for 24 h during the exponential growth of the algae. The ¹³C enrichment of eleven fatty acids was followed to understand the synthetic pathways the most likely to form the essential polyunsaturated fatty acids 20:5n-3 (EPA) and 22:6n-3 (DHA) in T. lutea. The fatty acids 16:0, 18:1n-9 + 18:3n-3, 18:2n-6, and 22:5n-6 were the most enriched in ¹³C. On the contrary, 18:4n-3 and 18:5n-3 were the least enriched in ¹³C after long chain polyunsaturated fatty acids such as 20:5n-3 or 22:5n-3. The algae appeared to use different routes in parallel to form its polyunsaturated fatty acids. The use of the PKS pathway was hypothesized for polyunsaturated fatty acids with n-6 configuration (such as 22:5n-6) but might also exist for n-3 PUFA (especially 20:5n-3). With regard to the conventional n-3 PUFA pathway, Δ6 desaturation of 18:3n-3 appeared to be the most limiting step for T. lutea, “stopping” at the synthesis of 18:4n-3 and 18:5n-3. These two fatty acids were hypothesized to not undergo any further reaction of elongation and desaturation after being formed and were therefore considered “end-products”. To circumvent this limiting synthetic route, Tisochrysis lutea seemed to have developed an alternative route via Δ8 desaturation to produce longer chain fatty acids such as 20:5n-3 and 22:5n-3. 22:6n-3 presented a lower enrichment and appeared to be produced by a combination of different pathways: the conventional n-3 PUFA pathway by desaturation of 22:5n-3, the alternative route of ω-3 desaturase using 22:5n-6 as precursor, and possibly the PKS pathway. In this study, PKS synthesis looked particularly effective for producing long chain polyunsaturated fatty acids. The rate of enrichment of these compounds hypothetically synthesized by PKS is remarkably fast, making undetectable the ¹³C incorporation into their precursors. Finally, we identified a protein cluster gathering PKS sequences of proteins that are hypothesized allowing n-3 PUFA synthesis.

Duplex Structure of Double-Stranded RNA Provides Stability against Hydrolysis Relative to Single-Stranded RNA

Phosphodiester bonds in the backbones of double-stranded (ds)RNA and single-stranded (ss)RNA are known to undergo alkaline hydrolysis. Consequently, dsRNA agents used in emerging RNA interference (RNAi) products have been assumed to exhibit low chemical persistence in solutions. However, the impact of the duplex structure of dsRNA on alkaline hydrolysis has not yet been evaluated. In this study, we demonstrated that dsRNA undergoes orders-of-magnitude slower alkaline hydrolysis than ssRNA. Furthermore, we observed that dsRNA remains intact for multiple months at neutral pH, challenging the assumption that dsRNA is chemically unstable. In systems enabling both enzymatic degradation and alkaline hydrolysis of dsRNA, we found that increasing pH effectively attenuated enzymatic degradation without inducing alkaline hydrolysis that was observed for ssRNA. Overall, our findings demonstrated, for the first time, that key degradation pathways of dsRNA significantly differ from those of ssRNA. Consideration of the unique properties of dsRNA will enable greater control of dsRNA stability during the application of emerging RNAi technology and more accurate assessment of its fate in environmental and biological systems, as well as provide insights into broader application areas including dsRNA isolation, detection and inactivation of dsRNA viruses, and prebiotic molecular evolution.

Microalgae n-3 PUFAs Production and Use in Food and Feed Industries

N-3 polyunsaturated fatty acids (n-3 PUFAs), and especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are essential compounds for human health. They have been proven to act positively on a panel of diseases and have interesting anti-oxidative, anti-inflammatory or anti-cancer properties. For these reasons, they are receiving more and more attention in recent years, especially future food or feed development. EPA and DHA come mainly from marine sources like fish or seaweed. Unfortunately, due to global warming, these compounds are becoming scarce for humans because of overfishing and stock reduction. Although increasing in recent years, aquaculture appears insufficient to meet the increasing requirements of these healthy molecules for humans. One alternative resides in the cultivation of microalgae, the initial producers of EPA and DHA. They are also rich in biochemicals with interesting properties. After defining macro and microalgae, this review synthesizes the current knowledge on n-3 PUFAs regarding health benefits and the challenges surrounding their supply within the environmental context. Microalgae n-3 PUFA production is examined and its synthesis pathways are discussed. Finally, the use of EPA and DHA in food and feed is investigated. This work aims to define better the issues surrounding n-3 PUFA production and supply and the potential of microalgae as a sustainable source of compounds to enhance the food and feed of the future.

Electro-Fenton Based Technique to Enhance Cell Harvest and Lipid Extraction from Microalgae

Currently, lipid extraction remains a major bottleneck in microalgae technology for biofuel production. In this study, an effective and easily controlled cell wall disruption method based on electro-Fenton reaction was used to enhance lipid extraction from the wet biomass of Nannochloropsis oceanica IMET1. The results showed that 1.27 mM of hydroxide radical (HO•) was generated under the optimal conditions with 9.1 mM FeSO4 in a 16.4 mA·cm−2 current density for 37.0 min. After the electro-Fenton treatment, the neutral lipid extraction yield of microalgae (~155 mg) increased from 40% to 87.5%, equal to from 12.2% to 26.7% dry cell weight (DCW). In particular, the fatty acid composition remained stable. The cell wall disruption and lipid extraction processes were displayed by the transmission electron microscope (TEM) and fluorescence microscopy (FM) observations, respectively. Meanwhile, the removal efficiency of algal cells reached 85.2% within 2 h after the reaction was terminated. Furthermore, the biomass of the microalgae cultured in the electrolysis wastewater treated with fresh nutrients reached 3 g/L, which is 12-fold higher than that of the initial after 24 days. These finds provided an economic and efficient method for lipid extraction from wet microalgae, which could be easily controlled by current magnitude regulation.

Enhancement of linoleic acid content stimulates astaxanthin esterification in Coelastrum sp

Most natural astaxanthin is fatty acid-esterified in microalgae to prevent oxidation. However, the factors influencing astaxanthin esterification (AE) are poorly understood. In this study, obstacles to AE in Coelastrum sp. HA-1 were investigated. Only half of the astaxanthin molecules in HA-1 were esterified, but AE was stimulated with exogenous linoleic acid (LA) and ethanol treatment. Astaxanthin esters and total astaxanthin (TA) with exogenous LA were elevated to 3.82-fold and 2.18-fold of control levels, respectively. Treatment with 3% (v/v) ethanol enhanced transcription of the Δ12 fatty acid desaturase gene, which caused more oleic acid (OA) to be converted to LA. Furthermore, the contents of astaxanthin esters and TA were 2.42-fold and 1.61-fold control levels, respectively. These findings confirmed that AE was upregulated by increasing LA content. Thus, a large concentration of OA alone does not increase astaxanthin accumulation in HA-1, and a certain amount of LA was necessary for AE.

EFSA Panel on Biological Hazards (BIOHAZ), Koutsoumanis K, Allende A, Alvarez‐Ordóñez A, Bolton D, Bover‐Cid S, Chemaly M, Davies R, De Cesare A, Hilbert F, Lindqvist R, Nauta M, Peixe L, Ru G, Simmons M, Skandamis P, Suffredini E, Cocconcelli PS, Fernández Escámez PS, Maradona MP, Querol A, Suarez JE, Sundh I, Vlak J, Barizzone F, Correia S, Herman L. Scientific Opinion on the update of the list of QPS-recommended biological agents intentionally added to food or feed as notified to EFSA (2017-2019)

The qualified presumption of safety (QPS) was developed to provide a safety pre-assessment within EFSA for microorganisms. Strains belonging to QPS taxonomic units (TUs) still require an assessment based on a specific data package, but QPS status facilitates fast track evaluation. QPS TUs are unambiguously defined biological agents assessed for the body of knowledge, their safety and their end use. Safety concerns are, where possible, to be confirmed at strain or product level, and reflected as 'qualifications'. Qualifications need to be evaluated at strain level by the respective EFSA units. The lowest QPS TU is the species level for bacteria, yeasts and protists/algae, and the family for viruses. The QPS concept is also applicable to genetically modified microorganisms used for production purposes if the recipient strain qualifies for the QPS status, and if the genetic modification does not indicate a concern. Based on the actual body of knowledge and/or an ambiguous taxonomic position, the following TUs were excluded from the QPS assessment: filamentous fungi, oomycetes, streptomycetes, Enterococcus faecium, Escherichia coli and bacteriophages. The list of QPS-recommended biological agents was reviewed and updated in the current opinion and therefore now becomes the valid list. For this update, reports on the safety of previously assessed microorganisms, including bacteria, yeasts and viruses (the latter only when used for plant protection purposes) were reviewed, following an Extensive Literature Search strategy. All TUs previously recommended for 2016 QPS list had their status reconfirmed as well as their qualifications. The TUs related to the new notifications received since the 2016 QPS opinion was periodically evaluated for QPS status in the Statements of the BIOHAZ Panel, and the QPS list was also periodically updated. In total, 14 new TUs received a QPS status between 2017 and 2019: three yeasts, eight bacteria and three algae/protists.

EFSA Panel on Biological Hazards (BIOHAZ), Koutsoumanis K, Allende A, Alvarez‐Ordóñez A, Bolton D, Bover‐Cid S, Chemaly M, Davies R, De Cesare A, Hilbert F, Lindqvist R, Nauta M, Peixe L, Ru G, Simmons M, Skandamis P, Suffredini E, Cocconcelli PS, Fernández Escámez PS, Maradona MP, Querol A, Suarez JE, Sundh I, Vlak J, Barizzone F, Correia S, Herman L. Update of the list of QPS-recommended biological agents intentionally added to food or feed as notified to EFSA 11: suitability of taxonomic units notified to EFSA until September 2019

Qualified presumption of safety (QPS) was developed to provide a generic safety evaluation for biological agents to support EFSA's Scientific Panels. The taxonomic identity, body of knowledge, safety concerns and antimicrobial resistance are assessed. Safety concerns identified for a taxonomic unit (TU) are where possible to be confirmed at strain or product level, reflected by 'qualifications'. No new information was found that would change the previously recommended QPS TUs and their qualifications. The list of microorganisms notified to EFSA was updated with 54 biological agents, received between April and September 2019; 23 already had QPS status, 14 were excluded from the QPS exercise (7 filamentous fungi, 6 Escherichia coli, Sphingomonas paucimobilis which was already evaluated). Seventeen, corresponding to 16 TUs, were evaluated for possible QPS status, fourteen of these for the first time, and Protaminobacter rubrum, evaluated previously, was excluded because it is not a valid species. Eight TUs are recommended for QPS status. Lactobacillus parafarraginis and Zygosaccharomyces rouxii are recommended to be included in the QPS list. Parageobacillus thermoglucosidasius and Paenibacillus illinoisensis can be recommended for the QPS list with the qualification 'for production purposes only' and absence of toxigenic potential. Bacillus velezensis can be recommended for the QPS list with the qualification 'absence of toxigenic potential and the absence of aminoglycoside production ability'. Cupriavidus necator, Aurantiochytrium limacinum and Tetraselmis chuii can be recommended for the QPS list with the qualification 'production purposes only'. Pantoea ananatis is not recommended for the QPS list due to lack of body of knowledge in relation to its pathogenicity potential for plants. Corynebacterium stationis, Hamamotoa singularis, Rhodococcus aetherivorans and Rhodococcus ruber cannot be recommended for the QPS list due to lack of body of knowledge. Kodamaea ohmeri cannot be recommended for the QPS list due to safety concerns.

Fed-batch fermentation of mixed carbon source significantly enhances the production of docosahexaenoic acid in Thraustochytriidae sp. PKU#Mn16 by differentially regulating fatty acids biosynthetic pathways

This study reports comparative evaluation of the growth and DHA productivity of the thraustochytrid strain Thraustochytriidae PKU#Mn16 fermented with seven different substrate feeding strategies. Of these strategies, fed-batch fermentation of the mixed substrate (glucose & glycerol) yielded the maximum growth (52.2 ± 1.5 g/L), DHA yield (Y_p/s: 8.65) and productivity (100.7 ± 2.9 mg/L-h), comparable with those of previously reported Aurantiochytrium strains. Transcriptomics analyses revealed that glucose upregulated some genes of the fatty acid synthase pathway whereas glycerol upregulated a few genes of the polyketide synthase pathway. Co-fermentation of the mixed substrate differentially regulated genes of these two pathways and significantly enhanced the DHA productivity. Furthermore, some genes involved in DNA replication, phagosome, carbon metabolism, and β-oxidation were also found to alter significantly during the mixed-substrate fermentation. Overall, this study provides a unique strategy for enhancing growth and DHA productivity of the strain PKU#Mn16 and the first insight into the mechanisms underlying mixed-substrate fermentation.

Lipid Distribution Pattern and Transcriptomic Insights Revealed the Potential Mechanism of Docosahexaenoic Acid Traffics in Schizochytrium sp. A-2

Schizochytrium sp. A-2 is a heterotrophic marine fungus used for the commercial production of docosahexaenoic acid (DHA). However, the pattern of the distribution of DHA and how DHA is channeled into phospholipid (PL) and triacylglycerol (TAG) are unknown. In this study, we systematically analyzed the distribution of DHA in TAG and PL during the growth of the cell. The migration of DHA from PL to TAG was presumed during the fermentation cycle. DHA and docosapentaenoic acid were accumulated in both TAG and phosphatidylcholine (PC), whereas eicosapentaenoic acid was mainly deposited in PC. RNA seq revealed that malic enzyme may provide lipogenic NADPH. In addition, long-chain acyl-CoA synthase and acyl-CoA:lysophosphatidylcholine acyltransferase may participate in the accumulation of DHA in PL. No phosphatidylcholine:diacylglycerol cholinephosphotransferase was identified from the genome sequence. In contrast, phospholipid:diacylglycerol acyltransferase-mediated acyl-CoA-independent TAG synthesis pathway and phospholipase C may contribute to the channeling of DHA from PC to TAG.

Enhanced saturated fatty acids accumulation in cultures of newly-isolated strains of Schizochytrium sp. and Thraustochytriidae sp. for large-scale biodiesel production

Heterotrophic marine protists (Thraustochytrids) have received increasingly global attention as a renewable, sustainable and alternative source of biodiesel because of their high ability of saturated fatty acids (SFAs) accumulation. Yet, the influence of extrinsic factors (nutrients and environmental conditions) on thraustochytrid culture and optimal conditions for high SFAs production are poorly described. In the present study, two different thraustochytrid strains, Schizochytrium sp. PKU#Mn4 and Thraustochytriidae sp. PKU#Mn16 were studied for their growth and SFAs production profiles under various conditions (carbon, nitrogen, temperature, pH, KH₂PO₄, salinity, and agitation speed). Of the culture conditions, substrates (C and N) source and conc., temperature, and agitation speed significantly influenced the cell growth and SFAs production of both strains. Although both the strains were capable of growth and SFAs production in the broad range of culture conditions, their physiological responses to KH₂PO₄, pH, and salinity were dissimilar. Under their optimal batch culture conditions, peak SFAs productions of 3.3g/L and 2.2g/L with 62% and 49% SFAs contents (relative to total fatty acids) were achieved, respectively. The results of 5-L fed-batch fermentation under optimal conditions showed a nearly 4.5-fold increase in SFAs production (i.e., 7.5g/L) by both strains compared to unoptimized conditions. Of the two strains, the quality of biodiesel produced from the fatty acids of PKU#Mn4 met the biodiesel standard defined by ASTM6751. This study, to the knowledge of the authors, is the first comprehensive report of optimal fermentation conditions demonstrating enhanced SFAs production by strains belonging to two different thraustochytrid genera and provides the basis for large-scale biodiesel production.

Effects of Cyclic Fatty Acid Monomers from Heated Vegetable Oil on Markers of Inflammation and Oxidative Stress in Male Wistar Rats

This study assesses the effects of cyclic fatty acid monomers (CFAM) from heated vegetable oils on oxidative stress and inflammation. Wistar rats were fed either of these four diets for 28 days: canola oil (CO), canola oil and 0.5% CFAM (CC), soybean oil (SO), and soybean oil and 0.5% CFAM (SC). Markers of oxidative stress and inflammation were determined by micro liquid chromatography tandem mass spectrometry (micro-LC-MS/MS) and enzyme-linked immunosorbent assay (ELISA) kits, respectively. Analysis of variance (ANOVA) for a 2 × 2 factorial design was performed to determine the CFAM and oil effects and interactions between these two factors at P ≤ 0.05. For significant interactions, a post hoc multiple comparison test was performed, i.e., Tukey HSD (honest significant difference) test. CFAM induced higher plasma levels of 15-F_2t-IsoP (CC, 396 ± 43 ng/mL, SC, 465 ± 75 ng/mL vs CO, 261 ± 23 ng/mL and SO, 288 ± 35 ng/mL, P < 0.05). Rats fed the SC diet had higher plasma 2,3-dinor-15-F_2t-IsoP (SC, 145 ± 9 ng/mL vs CC, 84 ± 8 ng/mL, CO, 12 ± 1 ng/mL, and SO, 12 ± 1 ng/mL, P < 0.05), urinary 2,3-dinor-15-F_2t-IsoP (SC, 117 ± 12 ng/mL vs CC, 67 ± 13 ng/mL, CO, 15 ± 2 ng/mL, and SO, 18 ± 4 ng/mL, P < 0.05), and plasma IL-6 (SC, 57 ± 10 pg/mL vs CC, 48 ± 11 pg/mL, CO, 46 ± 9 pg/mL, and SO, 44 ± 4 pg/mL, P < 0.05) than the other three diet groups. These results indicate that CFAM increased the levels of markers of oxidative stress, and those effects are exacerbated by a CFAM-high-linoleic acid diet.