Lipid Extraction Procedure Research Articles

A laboratory efficient method for intramuscular fat analysis

A new procedure to extract intramuscular fat (IMF) was developed to minimize sample amount, solvent use and time of analysis. Lyophilised samples (200mg) were accurately weighed in a safe-lock micro test tube, homogenized in 1.5mL dichloromethane-methanol (8:2) and mixed in a mixer mill (MM400, Retsch technology). The final biphasic system was separated by centrifugation (8min, 10,000rpm). The extraction was repeated three times. Solvent was evaporated under nitrogen stream and lipid content was gravimetrically determined. Results from 64 determinations were compared to those obtained with other referred method and showed a linear response over the whole range of IMF content (1.6–6.9g/100g sample). Moreover, the analysis with different methodology of six replica from the same sample showed lowest variability (standard deviation intra-method) for the new methodology proposed over a wide range of IMF content. A cost and time efficient lipid extraction procedure was developed without loss of precision and accuracy and with a fatty acid profile comparable to other protocols.

Comparison of various microalgae liquid biofuel production pathways based on energetic, economic and environmental criteria

In view of the increasing demand for bioenergy, in this study, the techno-economic viabilities for three emerging pathways to microalgal biofuel production have been evaluated. The three processes evaluated are the hydrothermal liquefaction (HTL), oil secretion and alkane secretion. These three routes differ in their lipid extraction procedure and the end-products produced. This analysis showed that these three processes showed various advantages: possibility to convert the defatted microalgae into bio-crude via HTL thus increasing the total biodiesel yield; better energetic and environmental performance for oil secretion and an even increased net energy ratio (NER) for alkane secretion. However, great technological breakthroughs are needed before planning any scale-up strategy such as continuous wet biomass processing and heat exchange optimization for the HTL pathway and effective and sustainable excretion for both secretion pathways.

New procedure for extraction of algal lipids from wet biomass: A green clean and scalable process

A new procedure, called Simultaneous Distillation and Extraction Process (SDEP), for lipid extraction from wet microalgae (Nannochloropsis oculata and Dunaliella salina) was reported. This method does not require a pre-drying of the biomass and employs alternative solvents such as d-limonene, α-pinene and p-cymene. This procedure has been compared with Soxhlet extraction (Sox) and Bligh & Dyer method (B&D). For N. oculata, results showed that SDEP-cymene provided similar lipid yields to B&D (21.45% and 23.78%), while SDEP-limonene and pinene provided lower yields (18.73% and 18.75% respectively). For D. salina, SDEP-pinene provided the maximum lipid yield (3.29%) compared to the other solvents, which is quite close to B&D result (4.03%). No significant differences in terms of distribution of lipid classes and fatty acid composition have been obtained for different techniques. Evaluation of energy consumption indicates a substantial saving in the extraction cost by SDEP compared to the conventional extraction technique, Soxhlet.

Biodiesel from mixed culture algae via a wet lipid extraction procedure

Microalgae are a source of renewable oil for liquid fuels. However, costs for dewatering/drying, extraction, and processing have limited commercial scale production of biodiesel from algal biomass. A wet lipid extraction procedure was developed that was capable of extracting 79% of transesterifiable lipids from wet algal biomass (84% moisture) via acid and base hydrolysis (90°C and ambient pressures), and 76% of those extracted lipids were isolated, by further processing, and converted to FAMEs. Furthermore, the procedure was capable of removing chlorophyll contamination of the algal lipid extract through precipitation. In addition, the procedure generated side streams that serve as feedstocks for microbial conversion to additional bioproducts. The capability of the procedure to extract lipids from wet algal biomass, to reduce/remove chlorophyll contamination, to potentially reduce organic solvent demand, and to generate feedstocks for high-value bioproducts presents opportunities to reduce costs of scaling up algal lipid extraction for biodiesel production.

Cultivation of cyanobacteria for extraction of lipids

Abstract Cyanobacteria were cultivated in laboratory to determine CO2 fixation rates and for extraction of lipids. The experiments were carried out in 4 phases, namely: flask cultivation of Synechocystis aquatilis TISTR8612 (S. aquatilis) to determine their optimal growth conditions; batch experiments in airlift photo-bioreactor (PBR) for estimation of CO2 fixation rates; continuous experiments in airlift PBR to evaluate biomass production and CO2 fixation rates; and development of appropriate method for lipid extraction from S. aquatilis. Investigations revealed that the optimum conditions for cultivating S. aquatilis were: pH 8, temperature of 30 °C, and illuminance of 4 klx. Batch experiments conducted at 5% inlet CO2 yielded maximum CO2 fixation rate at space velocity of 14 min−1. On the other hand, continuous experiments in airlift PBR revealed optimum dilution rate of 0.012 d−1 with maximum biomass production rate of 932 mg L−1 d−1. Inlet CO2 concentration of 8% was found to be most suitable to yield CO2 fixation rate of 5.3 g L−1 d−1. Lipid extraction procedure comprising of sonication and solvent extraction (chloroform:methanol as 1:1 by volume) resulted in highest lipid yield of 18.58%. The extracted fatty acids were mostly composed of polyunsaturated fatty acids such as linoleic and α-linolenic acid.

Bryocella elongata gen. nov., sp. nov., a member of subdivision 1 of the Acidobacteria isolated from a methanotrophic enrichment culture, and emended description of Edaphobacter aggregans Koch et al. 2008

An aerobic, pink-pigmented, chemo-organotrophic bacterium, designated strain SN10(T), was isolated from a methanotrophic enrichment culture obtained from an acidic Sphagnum peat. This isolate was represented by Gram-negative, non-motile rods that multiply by normal cell division and form rosettes. Strain SN10(T) is an obligately acidophilic, mesophilic bacterium capable of growth at pH 3.2-6.6 (with an optimum at pH 4.7-5.2) and at 6-32 °C (with an optimum at 20-24 °C). The preferred growth substrates are sugars and several heteropolysaccharides of plant and microbial origin, such as pectin, lichenan, fucoidan and gellan gum. While not being capable of growth on C(1) compounds, strain SN10(T) can develop in co-culture with exopolysaccharide-producing methanotrophs by utilization of their capsular material. The major fatty acids determined in strain SN10(T) using the conventional lipid extraction procedure are iso-C(15:0) and C(16:1)ω7c. Upon hydrolysis of total cell material, substantial amounts of the uncommon membrane-spanning lipid 13,16-dimethyl octacosanedioic acid (isodiabolic acid) were also detected. The polar lipids are two phosphohexoses, phosphatidylethanolamine, phosphatidylglycerol and several phospholipids of unknown structure. The major quinone is MK-8. Pigments are carotenoids. The G+C content of the DNA is 60.7 mol%. Strain SN10(T) forms a separate lineage within subdivision 1 of the phylum Acidobacteria and displays 94.0-95.4% 16S rRNA gene sequence similarity to members of the genera Edaphobacter and Granulicella, 93.0-93.7% similarity to members of the genus Terriglobus and 92.2-92.3 % similarity to the type strains of Telmatobacter bradus and Acidobacterium capsulatum. Therefore, strain SN10(T) is classified within a novel genus and species, for which the name Bryocella elongata gen. nov., sp. nov. is proposed. Strain SN10(T) (=LMG 25276(T) =DSM 22489(T)) is the type strain of Bryocella elongata. An emended description of Edaphobacter aggregans Koch et al. 2008 is also given.

Accurate and reliable quantification of total microalgal fuel potential as fatty acid methyl esters by in situ transesterification

In the context of algal biofuels, lipids, or better aliphatic chains of the fatty acids, are perhaps the most important constituents of algal biomass. Accurate quantification of lipids and their respective fuel yield is crucial for comparison of algal strains and growth conditions and for process monitoring. As an alternative to traditional solvent-based lipid extraction procedures, we have developed a robust whole-biomass in situ transesterification procedure for quantification of algal lipids (as fatty acid methyl esters, FAMEs) that (a) can be carried out on a small scale (using 4–7 mg of biomass), (b) is applicable to a range of different species, (c) consists of a single-step reaction, (d) is robust over a range of different temperature and time combinations, and (e) tolerant to at least 50% water in the biomass. Unlike gravimetric lipid quantification, which can over- or underestimate the lipid content, whole biomass transesterification reflects the true potential fuel yield of algal biomass. We report here on the comparison of the yield of FAMEs by using different catalysts and catalyst combinations, with the acid catalyst HCl providing a consistently high level of conversion of fatty acids with a precision of 1.9% relative standard deviation. We investigate the influence of reaction time, temperature, and biomass water content on the measured FAME content and profile for 4 different samples of algae (replete and deplete Chlorella vulgaris, replete Phaeodactylum tricornutum, and replete Nannochloropsis sp.). We conclude by demonstrating a full mass balance closure of all fatty acids around a traditional lipid extraction process. FigureAccurate quantification of different types of lipids in algal biomass using a comprehensive study of reaction parameters. Electronic supplementary materialThe online version of this article (doi:10.1007/s00216-012-5814-0) contains supplementary material, which is available to authorized users.

Enhancement of Lipid Extraction from Marine Microalga,ScenedesmusAssociated with High-Pressure Homogenization Process

Marine microalga, Scenedesmus sp., which is known to be suitable for biodiesel production because of its high lipid content, was subjected to the conventional Folch method of lipid extraction combined with high-pressure homogenization pretreatment process at 1200 psi and 35°C. Algal lipid yield was about 24.9% through this process, whereas only 19.8% lipid can be obtained by following a conventional lipid extraction procedure using the solvent, chloroform : methanol (2 : 1, v/v). Present approach requires 30 min process time and a moderate working temperature of 35°C as compared to the conventional extraction method which usually requires >5 hrs and 65°C temperature. It was found that this combined extraction process followed second-order reaction kinetics, which means most of the cellular lipids were extracted during initial periods of extraction, mostly within 30 min. In contrast, during the conventional extraction process, the cellular lipids were slowly and continuously extracted for >5 hrs by following first-order kinetics. Confocal and scanning electron microscopy revealed altered texture of algal biomass pretreated with high-pressure homogenization. These results clearly demonstrate that the Folch method coupled with high-pressure homogenization pretreatment can easily destruct the rigid cell walls of microalgae and release the intact lipids, with minimized extraction time and temperature, both of which are essential for maintaining good quality of the lipids for biodiesel production.

Optimization of an Analytical Procedure for Extraction of Lipids from Microalgae

AbstractAn optimized procedure for extraction of total and non‐polar lipids from microalgae is proposed. The effects of solvent, pretreatment (lyophilization, inactivation of lipases, and addition of antioxidants) and cell‐disruption (liquid nitrogen, sonication, and bead beating) on total lipid content, lipid class, and fatty acid composition were examined. Chloroform–methanol 1:1 was shown to be the best solvent mixture for extraction of total lipids from microalgae. When performing this extraction, lyophilized algae can be used, no pretreatment with isopropanol to inactivate the lipases is needed and addition of antioxidants is not necessary. Furthermore, cell‐disruption is not essential, although in that case two extractions must be performed in series to ensure that, irrespective of the microalgal species, all lipids are extracted. Determination of non‐polar lipid content should be performed by separation of the total lipid extract on an SPE column. Extraction using petroleum ether is only appropriate when a bead beater is used for pretreatment.

Enzymatic activity of the human 1-acylglycerol-3-phosphate-O-acyltransferase isoform 11: upregulated in breast and cervical cancers

The conversion of lysophosphatidic acid (LPA) to phosphatidic acid is carried out by the microsomal enzymes 1-acylglycerol-3-phosphate-O-acyltransferases (AGPATs). These enzymes are specific for acylating LPA at the sn-2 (carbon 2) position on the glycerol backbone and are important, because they provide substrates for the synthesis of phospholipids and triglycerides. At least, mutations in one isoform, AGPAT2, cause near complete loss of adipose tissue in humans. We cloned a cDNA predicted to be an AGPAT isoform, AGPAT11. This cDNA has been recently identified also as lysophosphatidylcholine acyltransferase 2 (LPCAT2) and lyso platelet-activating factor acetyltransferase. When AGPAT11/LPCAT2/lyso platelet-activating factor acetyltransferase cDNA was expressed in CHO and HeLa cells, the protein product localized to the endoplasmic reticulum. In vitro enzymatic activity using lysates of Human Embryonic Kidney-293 cells infected with recombinant AGPAT11/LPCAT2/lyso platelet-activating factor-acetyltransferase cDNA adenovirus show that the protein has an AGPAT activity but lacks glycerol-3-phosphate acyltransferase enzymatic activity. The AGPAT11 efficiently uses C18:1 LPA as acyl acceptor and C18:1 fatty acid as an acyl donor. Thus, it has similar substrate specificities for LPA and acyl-CoA as shown for AGPAT9 and 10. Expression of AGPAT11 mRNA was significantly upregulated in human breast, cervical, and colorectal cancer tissues, indicating its adjuvant role in the progression of these cancers. Our enzymatic assays strongly suggest that the cDNA previously identified as LPCAT2/lyso platelet-activating factor-acetyltransferase cDNA has AGPAT activity and thus we prefer to identify this clone as AGPAT11 as well.

Evaluation of Inhibitory Actions of Flavonols and Related Substances on Lysophospholipase D Activity of Serum Autotaxin by a Convenient Assay Using a Chromogenic Substrate

Overproduction of lysophosphatidic acid (LPA) by lysophospholipase D/autotaxin (lysoPLD/ATX) is postulated to be involved in the promotion of cancer and atherosclerosis. A lysoPLD inhibitor may be utilized to ameliorate the LPA-related pathological conditions. In this study, a new assay was devised to quantify p-nitrophenol from hydrolysis of chromogenic substrate by serum lysoPLD without tedious lipid extraction procedures. Flavonols, phenolic acids, free fatty acids, and N-acyltyrosines inhibited lysoPLD activity in a micromolar range. They were classified into competitive, noncompetitive, or mixed type inhibitors. The results show that the low hydrophobicity of an inhibitor is a critical factor in its preference for the binding to a noncatalytic binding site over a catalytic binding site. Considering its reported bioavailability and the low dependency of its inhibitory activity on serum dilution, flavonol is likely to be a more effective lysoPLD inhibitor in human blood circulation in vivo than the other inhibitors including LPA.

Improved method for the quantification of lysophospholipids including enol ether species by liquid chromatography-tandem mass spectrometry

LC/ESI-MS/MS has been previously demonstrated to be a powerful method to detect and quantify molecular species of glycerophospholipids including lysophospholipids. In this study, we provide an improved pre-mass spectrometry lipid extraction procedure that avoids the acid-catalyzed decomposition of plasmenyl phospholipids that is problematic with previously reported methods. We show that the use of lysophospholipid internal standards with perdeuterated fatty acyl chains avoids isobar problems associated with the use of internal standards containing odd carbon number fatty acyl chains. We also show that LC prior to MS is required to avoid numerous problems associated with isobars and with MS in-source decomposition of lysophosphatidylserine. The reported method of using normal phase chromatography/ESI-MS is used to quantify lysophospholipids in serum and to quantify lysophospholipids produced in mammalian cells by human group X secreted phospholipase A(2). The latter shows that group X phospholipase A(2) added exogenously to cells generates a different set of lysophospholipids compared with enzyme produced endogenously in cells, which supports earlier studies showing that this phospholipase A(2) can act on cell membranes prior to externalization from cells.

Effects of Lipid Extraction on Stable Isotope Ratios in Avian Egg Yolk: Is Arithmetic Correction a Reliable Alternative?

ABSTRACT. Many studies of nutrient allocation to egg production in birds use stable isotope ratios of egg yolk to identify the origin of nutrients. Dry egg yolk contains >50% lipids, which are known to be depleted in 13C. Currently, researchers remove lipids from egg yolk using a chemical lipid-extraction procedure before analyzing the isotopic composition of protein in egg yolk. We examined the effects of chemical lipid extraction on δ13C, δ15N, and δ34S of avian egg yolk and explored the utility of an arithmetic lipid correction model to adjust whole yolk δ13C for lipid content. We analyzed the dried yolk of 15 captive Spectacled Eider (Somateria fischeri) and 20 wild King Eider (S. spectabilis) eggs, both as whole yolk and after lipid extraction with a 2:1 chloroform:methanol solution. We found that chemical lipid extraction leads to an increase of (mean ± SD) 3.3 ± 1.1‰ in δ13C, 1.1 ± 0.5‰ in δ15N, and 2.3 ± 1.1‰ in δ34S. Arithmetic lipid correction provided accurate values for lipid-extracted δ13C in...

The Spectrum of Plant and Animal Sterols in Different Oil‐Derived Intravenous Emulsions

Intravenous lipid constituents have different effects on various biological processes. Some of these effects are protective, while others are potentially adverse. Phytosterols, in particular, seem to be implicated with parenteral nutrition-associated cholestasis. The aim of this study is to determine the amount of plant and animal sterols present in lipid formulations derived from different oil sources. To this end, animal (cholesterol) and plant (beta-sitosterol, campesterol, and stigmasterol) sterols in seven different commercially available intravenous lipid emulsions (ILEs) were quantified by capillary gas chromatography after performing a lipid extraction procedure. The two major constituents of the lipid emulsions were cholesterol (range 14-57% of total lipids) and beta-sitosterol (range 24-55%), followed by campesterol (range 8-18%) and stigmasterol (range 5-16%). The fish oil-derived formulation was an exception, as it contained only cholesterol. The mean values of the different sterols were statistically different across ILEs (P = 0.0000). A large percentage of pairwise comparisons were also statistically significant (P = 0.000), most notably for cholesterol and stigmasterol (14 out of 21 for both), followed by campesterol (12 out 21) and beta-sitosterol (11 out 21). In conclusion, most ILEs combined significant amounts of phytosterols and cholesterol. However, their phytosterols:cholesterol ratios were reversed compared to the normal human diet.

The fish of Lake Titicaca: implications for archaeology and changing ecology through stable isotope analysis

Research on past human diets in the southern Lake Titicaca Basin has directed us to investigate the carbon and nitrogen stable isotopes of an important dietary element, fish. By completing a range of analyses on modern and archaeological fish remains, we contribute to two related issues regarding the application of stable isotope analysis of archaeological fish remains and in turn their place within human diet. The first issue is the potential carbon and nitrogen isotope values of prehistoric fish (and how these would impact human dietary isotopic data), and the second is the observed changes in the fish isotopes through time. Out of this work we provide quantitative isotope relationships between fish tissues with and without lipid extraction, and a qualitative analysis of the isotopic relationships between fish tissues, allowing archaeologists to understand these relationships and how these values can be applied in future research. We test a mathematical lipid normalization equation to examine whether future researchers will need to perform lipid extraction procedures for Lake Titicaca fish. We also analyze a number of aquatic plants to better understand the range of isotopic signatures of the Lake Titicaca ecosystem. We use these data to better understand prehistoric human diet and the role that fish may have played in the past as well as potential changes in local lake ecology through time.

Chemical analysis of atherosclerotic plaque cholesterol combined with histology of the same tissue

Sensitive method for chemical analysis of free cholesterol (FC) and cholesterol esters (CE) was developed. Mouse arteries were dissected and placed in chloroform-methanol without tissue grinding. Extracts underwent hydrolysis of cholesteryl esters and derivatization of cholesterol followed by liquid chromatography/mass spectrometry (LC/MS/MS) analysis. We demonstrated that FC and CE could be quantitatively extracted without tissue grinding and that lipid extraction simultaneously worked for tissue fixation. Delipidated tissues can be embedded in paraffin, sectioned, and stained. Microscopic images obtained from delipidated arteries have not revealed any structural alterations. Delipidation was associated with excellent antigen preservation compatible with traditional immunohistochemical procedures. In ApoE(-/-) mice, LC/MS/MS revealed early antiatherosclerotic effects of dual PPARalpha,gamma agonist LY465606 in brachiocephalic arteries of mice treated for 4 weeks and in ligated carotid arteries of animals treated for 2 weeks. Reduction in CE and FC accumulation in atherosclerotic lesions was associated with the reduction of lesion size. Thus, a combination of LC/MS/MS measurements of CE and FC followed by histology and immunohistochemistry of the same tissue provides novel methodology for sensitive and comprehensive analysis of experimental atherosclerotic lesions.

Modification of the oxidative stress biomarker AOPP assay: Application in uremic samples

Background The levels of advanced oxidation protein products (AOPP), a plasma protein biomarker used to assess oxidative stress, are elevated in patients with chronic kidney disease (CKD). However, this apparent elevation is to a large extent due to assay interference (mostly by triglycerides which are usually markedly elevated in CKD). We therefore developed and tested a modified version of the AOPP assay to minimize the impact of this interference. Methods Plasma levels of AOPP, lipids, proteins and various biomarkers of inflammation and oxidative stress were analyzed in 218 prevalent hemodialysis patients and 13 healthy controls using the established original ( oAOPP) assay and following precipitation of plasma lipids using dextran sulphate (modified assay, mAOPP). The modified results were validated against a lipid extraction procedure using ether/butanol. Results The modified assay decreased the levels of triglycerides and AOPP by 87% and 38%, respectively. Whereas oAOPP values correlated strongly with triglycerides, no such correlation was seen with mAOPP. The mAOPP levels correlated significantly with the oxidative stress markers 8-oxo-dG and pentosidine, whereas no such correlations were found for oAOPP. Conclusions The oAOPP concentration is largely overestimated in plasma samples due to lipid interferences. Precipitation of triglycerides before analysis yields markedly lower mAOPP values which more accurately reflect oxidative stress. Based on these results we propose that AOPP should be analyzed using the modified assay, which is a cheap, simple and fast method.

A MYB Transcription Factor Regulates Very-Long-Chain Fatty Acid Biosynthesis for Activation of the Hypersensitive Cell Death Response inArabidopsis

Plant immune responses to pathogen attack include the hypersensitive response (HR), a form of programmed cell death occurring at invasion sites. We previously reported on Arabidopsis thaliana MYB30, a transcription factor that acts as a positive regulator of a cell death pathway conditioning the HR. Here, we show by microarray analyses of Arabidopsis plants misexpressing MYB30 that the genes encoding the four enzymes forming the acyl-coA elongase complex are putative MYB30 targets. The acyl-coA elongase complex synthesizes very-long-chain fatty acids (VLCFAs), and the accumulation of extracellular VLCFA-derived metabolites (leaf epidermal wax components) was affected in MYB30 knockout mutant and overexpressing lines. In the same lines, a lipid extraction procedure allowing high recovery of sphingolipids revealed changes in VLCFA contents that were amplified in response to inoculation. Finally, the exacerbated HR phenotype of MYB30-overexpressing lines was altered by the loss of function of the acyl-ACP thioesterase FATB, which causes severe defects in the supply of fatty acids for VLCFA biosynthesis. Based on these findings, we propose a model in which MYB30 modulates HR via VLCFAs by themselves, or VLCFA derivatives, as cell death messengers in plants.

Validation of a gas chromatography–mass spectrometry method for the analysis of sterol oxidation products in serum

A validated gas chromatography–mass spectrometry (GC–MS) detection method for the quantitative analysis of sterol oxidation products (SOPs) in serum is described. After a lipid extraction procedure with chloroform–methanol, a cold saponification and purification by solid phase extraction, oxysterols were derivatizated to form trimethyl-sylil-ethers which were subjected to GC–MS analysis. Calibration curves for cholesterol oxidation products showed determination coefficient ( R 2) of 1.0, with low values for the coefficient of variation of the response factors (<1%). Detection and quantification limits were below 5 ng/mL and 10 ng/mL, respectively. Recovery data were between 77.65% and 110.29% (CV < 10% for all compounds). Good results were obtained for within- and between-day repeatability, with values below 10%. In conclusion, the method performed is suitable for the determination and quantification of SOPs in serum.

Supplemental algal meal alters the ruminal trans-18:1 fatty acid and conjugated linoleic acid composition in cattle1

The effects of dietary algal supplementation, a source of docosahexaenoic acid, on the fatty acid profile of rumen lipids in cattle were evaluated, with special emphasis on CLA and trans fatty acids produced by rumen microbes. A diet based on corn silage was fed with supplements containing the following: 1) no algal meal and fed at 2.1 kg of DM/d (control), 2) algal meal and fed at 1.1 kg of DM/d (low algal meal), 3) algal meal and fed at 2.1 kg of DM/d (medium algal meal), and 4) algal meal and fed at 4.2 kg of DM/d (high algal meal). A modified lipid extraction procedure was developed to analyze the lipid changes in rumen fluid. The percentage of stearic acid (18:0) in rumen fluid was decreased by algal meal supplementation (P < 0.001) compared with control and was linearly dependent on the level of algal meal supplementation (P = 0.005). Total trans-18:1 in rumen fluid of cattle fed the control diet was 19% of total fatty acids. Addition of algal meal increased (P < 0.001) total trans-18:1 up to 43%, mostly due to 18:1 trans-10 that increased (P = 0.002) to 29.5% of total rumen fatty acids. This increase in 18:1 trans-10 seems to suggest a change in the rumen microbial population. Vaccenic acid (18:1 trans-11) increased quadratically (P = 0.005) with increasing level of algal meal supplementation in the diets. The total CLA content was low in the control (<0.9%) and increased with dietary algal meal addition, although not significantly; the greatest level was 1.5% with the medium algal meal diet. The increase of rumenic acid (cis-9, trans-11 CLA) was quadratic (P = 0.05) with algal meal supplementation, whereas trans-10, cis-12 CLA increased linearly with increased level of algal meal from 0.08 to 0.13% (P = 0.03). The ratio of trans-11 (cis-9, trans-11 CLA + 18:1 trans-11) to trans-10 (trans-10, cis-12 CLA + 18:1 trans-10) decreased from 2.45 to 0.77, 0.87, and 0.21 for the control, low algal meal, medium algal meal, and high algal meal diets, respectively. The content of docosahexaenoic acid in rumen fluid increased (P = 0.002) from 0.3 to 1.4% of total fatty acids with increasing level of algal meal supplementation in the diets. Our results suggest that algal meal inhibits the reduction of trans-18:1 to 18:0, giving rise to the high trans-18:1 content. In conclusion, algal meal could be used to increase the concentration in rumen contents of trans-18:1 isomers that serve as precursors for CLA biosynthesis in the tissues of ruminants.