Regiospecific identification of 2-(12-ricinoleoylricinoleoyl)-1,3-diricinoleoyl-sn-glycerol in castor (Ricinus communis L.) oil by ESI-MS(4)

(12-Ricinoleoylricinoleoyl)diricinoleoylglycerol (RRRR), a tetraacylglycerol, was identified earlier in castor oil. Using ESI-MS (4), 95% of the 12-ricinoleoylricinoleoyl chain was identified at the sn-2 position of the glycerol backbone of RRRR. Regiospecific location of the 12-ricinoleoylricinoleoyl chain of RRRR on the glycerol backbone was identified and quantified by the ions from the losses of the acyl chains at the sn-2 position as alpha,beta-unsaturated fatty acids from the lithium adduct of RRRR. The regiospecific location was confirmed by hydrolysis of RRRR using sn-1,3 specific lipase. By comparison to the mass spectrum of 1- O-palmityl-2,3-palmitoyl- rac-glycerol containing one ether bond, the 12-ricinoleoylricinoleoyl chain of RRRR is indeed the ester bond between the two ricinoleoyl chains, not the ether bond formed from the two hydroxyl groups of the two ricinoleoyl chains. The structure of RRRR is 2-(12-ricinoleoylricinoleoyl)-1,3-diricinoleoyl- sn-glycerol.     

Analysis of regiospecific triacylglycerols by electrospray ionization-mass spectrometry(3) of lithiated adducts

A method of regiospecific analysis of triacylglycerols (TAGs) in vegetable oils and animal fats is reported here using the electrospray ionization-mass spectrometry (MS(3)) of TAG-lithiated adducts. The fragment ions of the MS(3) from the loss of fatty acids at the sn-2 position as alpha,beta-unsaturated fatty acids were used for regiospecific identification and quantification. The ratio of the regiospecific TAGs, ABA and AAB, in an oil sample usually fraction collected by high-performance liquid chromatography can be determined by the abundance of the fragment ions of [ABA + Li-ACOOH-B'CH=CHCOOH]+ and [AAB + Li-ACOOH-A'CH=CHCOOH]+. The method was used to analyze regiospecific TAGs in extra virgin olive oil. The results showed that the saturated fatty acids, palmitic and stearic acids, were mostly located at the sn-1,3 positions and unsaturated fatty acids, oleic and linoleic acids, were mostly located at the sn-2 position.     

Comparison of the incorporation of oleate and ricinoleate into phosphatidylcholines and acylglycerols in soybean microsomes

The incorporations of oleate (endogenous) and ricinoleate (nonendogenous) into phosphatidylcholine (PC) and acylglycerol (AG) in immature soybean microsomes were compared. [(14)C]Oleate and [(14)C]ricinoleate were incubated individually with soybean microsomal preparations for up to 4 h, and molecular species of PC and AG incorporated were identified and quantified by HPLC. The activities of acyl CoA:lysoPC acyltransferase and phospholipase A(2) are in general not affected by the fatty acid (FA) chain at the sn-1 position. However, comparison between oleate and ricinoleate revealed that different FA incorporated at sn-2 of PC showed some different selection of the molecular species of lysoPC. The incorporation of [(14)C]ricinoleate into triacylglycerols (TAG) was slightly better than that of [(14)C]oleate and indicated that soybean was capable of incorporating ricinoleate into TAG when ricinoleate can be produced endogenously in a transgenic soybean. The incorporation of FA into TAG in soybean microsomes was much slower than that in castor microsomes.     

Changes in triacylglycerol composition during ripening of sea buckthorn (Hippophaë rhamnoides L.) seeds

Changes in the quantitative composition of triacylglycerols (TAGs) in maturing sea buckthorn (Hippopha? rhamnoides L.) seeds were determined by lipase hydrolysis. As a whole, the rate of synthesis of separate TAG classes increased in proportion to both their unsaturation and relative content (weight percent) in total TAGs. Up to the 80th day of maturation, the formation of triunsaturated TAGs was predominant. Subsequently, at the terminal stage of seed ripening, the absolute content (in nanomoles per seed) of a major group of these TAGs containing linolenic and linoleic acyls decreased by approximately 7%, and the increase in the total TAG content was mainly due to the synthesis of TAG molecules including stearic and palmitic acyls in the rac-1,3 positions, as well as those containing oleate in the sn-2 position. At each maturation stage, the composition of the TAGs formed was controlled both by the composition of fatty acids available for TAG synthesis and by the rate of incorporation of a particular fatty acid into the sn-2 position of the TAGs.     

Stereospecific analysis of triacylglycerol and phospholipid fractions of five wild freshwater fish from Poyang Lake

The fatty acids (FA) compositions and positional distributions in triacylglycerols (TAG) and phospholipids (PL) of five wild freshwater fish (Squaliobarbus curriculus, Erythroculter ilishaeformis, Pseudobagrus fulvidraco, Bostrichthys sinensis, and Siniperca kneri Garman) from Poyang Lake (the largest freshwater lake of China) were studied. For TAG, S. kneri German had the highest content (13.59%) of n - 3 polyunsaturated fatty acids (PUFA) and E. ilishaeformis had the lowest ratio of (n - 6)/(n - 3) (0.65). PL had a high content of PUFA, which declined in the order of phosphatidylethanolamine (PE) > phosphatidylcholine (PC) > TAG. 9c11t-18:2 accounted for 6.38-50.77% of total conjugated linoleic acids (CLA). The highest level of odd-branched chain fatty acids (OBCFA) was 26.7% in B. sinensis. The study revealed that the distribution of FA among the sn positions was not random: monounsaturated fatty acids (MUFA) and PUFA preferred positions 1 and 3 and saturated fatty acids (SFA) position 2 of TAG, while SFA and MUFA predominated over sn-1-PL and PUFA over sn-2-PL.     

Isolation and characterization of neutral lipids of desilked eri silkworm pupae grown on castor and tapioca leaves

The neutral lipid of desilked eri silkworm pupae (Samia cynthia ricini) grown on two different host plants, castor (Ricinus communis Linn.) and tapioca (Manihot utilizsima Phol.) leaves, was extracted with hexane. The oil content in pupae was estimated to be in the range of 18-20% (dry basis). The pupal oil was found to be enriched with alpha-linolenic acid (ALA) with palmitic acid as the second major fatty acid. The level of ALA in the oil of silkworm pupae was found to be significantly higher (P < 0.001) when grown on tapioca (58.3%) as compared to those grown on castor (42.9%). Other chemical parameters such as percent free fatty acid, peroxide value, phosphorus content, percent unsaponifiable matter, and composition of sterols were also determined in both of the oils and compared. Reversed-phase high-performance liquid chromatography analysis of triacylglycerol molecular species showed that the pupal oil is rich in molecular species with equivalent carbon numbers (ECN) C36, C40, C42, C44, and C48. There was a significantly higher level (P < 0.001) of trilinolenin (C36) in the oil of tapioca-based silkworm as compared to castor-based silkworm pupae. Regiospecific analysis of the oil showed a higher level of ALA at the sn-2 position of silkworm pupae grown on tapioca (60.2%) as compared to those grown on castor (47.3%) oil. Thus, the presence of a large amount of ALA and their predominance at the sn-2 position make the eri pupal oil highly nutritious, provided that the oxidative stability is ensured.     

Lipase-catalyzed acidolysis of tripalmitin with hazelnut oil fatty acids and stearic acid to produce human milk fat substitutes

Structured lipids (SLs) containing palmitic, oleic, stearic, and linoleic acids, resembling human milk fat (HMF), were synthesized by enzymatic acidolysis reactions between tripalmitin, hazelnut oil fatty acids, and stearic acid. Commercially immobilized sn-1,3-specific lipase, Lipozyme RM IM, obtained from Rhizomucor miehei was used as the biocatalyst for the enzymatic acidolysis reactions. The effects of substrate molar ratio, reaction temperature, and reaction time on the incorporation of stearic and oleic acids were investigated. The acidolysis reactions were performed by incubating 1:1.5:0.5, 1:3:0.75, 1:6:1, 1:9:1.25, and 1:12:1.5 substrate molar ratios of tripalmitin/hazelnut oil fatty acids/stearic acid in 3 mL of n-hexane at 55, 60, and 65 degrees C using 10% (total weight of substrates) of Lipozyme RM IM for 3, 6, 12, and 24 h. The fatty acid composition of reaction products was analyzed by gas-liquid chromatography (GLC). The fatty acids at the sn-2 position were identified after pancreatic lipase hydrolysis and GLC analysis. The results showed that the highest C18:1 incorporation (47.1%) and highest C18:1/C16:0 ratio were obtained at 65 degrees C and 24 h of incubation with the highest substrate molar ratio of 1:12:1.5. The highest incorporation of stearic acid was achieved at a 1:3:0.75 substrate molar ratio at 60 degrees C and 24 h. For both oleic and stearic acids, the incorporation level increased with reaction time. The SLs produced in this study have potential use in infant formulas.     

Regioisomerism of triacylglycerols in lard, tallow, yolk, chicken skin, palm oil, palm olein, palm stearin, and a transesterified blend of palm stearin and coconut oil analyzed by tandem mass spectrometry.

Triacylglycerols (TAG) of lard, tallow, egg yolk, chicken skin, palm oil, palm olein, palm stearin, and a transesterified blend of palm stearin and coconut oil (82:18) were investigated by chemical ionization and collision-induced dissociation tandem mass spectrometry. Accurate molecular level information of the regioisomeric structures of individual TAGs was achieved. When existing in a TAG molecule of lard, palmitic acid occupied 90-100% of the sn-2 position. Within the major fatty acid combinations in tallow TAGs, the secondary position sn-2 was preferentially occupied in the decreasing order by oleoyl > palmitoyl > stearoyl residues, the order in saturated TAGs being myristoyl > stearoyl = palmitoyl. TAGs in egg yolk were more asymmetric than in chicken skin, with linoleic acid highly specifically attached in the yolk sn-2 carbon. Nearly 50% of yolk TAGs contained 52 carbon atoms with two or three double bonds. Linoleic, oleic, and palmitic acids were in the sn-2 location in decreasing quantities in palm oil and its fractions. Triacylglycerols of equal molecular weight behaved similarly in the fractionation process. Randomization of the parent oil TAGs was seen in the transesterified oil. The tandem mass spectrometric analysis applied provided detailed information of the distribution of fatty acids in individual combinations in TAGs.     

Lipase-catalyzed incorporation of different Fatty acids into tripalmitin-enriched triacylglycerols: effect of reaction parameters

Tripalmitin-enriched triacylglycerols were concentrated from palm stearin by acetone fractionation and as the substrate reacted with a mixture of equimolar quantities of fatty acids (C8:0-C18:3). The incorporation degree and acyl migration level of the fatty acids and acylglycerols composition were investigated, providing helpful information for the production of human milk fat substitutes. Higher incorporation degrees of the fatty acids were obtained with lipase PS IM, Lipozyme TL IM, and Lipozyme RM IM followed by porcine pancreatic lipase and Novozym 435-catalyzed acidolysis. During reactions catalyzed by Lipozyme TL IM, Lipozyme RM IM, and lipase PS IM, incorporation degrees of C12:0, C14:0, C18:1, and C18:2 were higher than those of other fatty acids at operated variables (molar ratio, temperature, and time), and the triacylglycerols content reached the highest (82.09%) via Lipozyme RM IM-catalyzed acidolysis. On the basis of significantly different levels of acyl migration to the sn-2 position, lipases were in the order of lipase PS IM < Lipozyme TL IM < Lipozyme RM IM.     

Screening of the entire USDA castor germplasm collection for oil content and fatty acid composition for optimum biodiesel production

Castor has tremendous potential as a feedstock for biodiesel production. The oil content and fatty acid composition in castor seed are important factors determining the price for production and affecting the key fuel properties of biodiesel. There are 1033 available castor accessions collected or donated from 48 countries worldwide in the USDA germplasm collection. The entire castor collection was screened for oil content and fatty acid composition by nuclear magnetic resonance (NMR) and gas chromatography (GC), respectively. Castor seeds on the average contain 48.2% oil with significant variability ranging from 37.2 to 60.6%. Methyl esters were prepared from castor seed by alkaline transmethylation. GC analysis of methyl esters confirmed that castor oil was composed primarily of eight fatty acids: 1.48% palmitic (C16:0), 1.58% stearic (C18:0), 4.41% oleic (C18:1), 6.42% linoleic (C18:2), 0.68% linolenic (C18:3), 0.45% gadoleic (C20:1), 84.51% ricinoleic (C18:1-1OH), and 0.47% dihydroxystearic (C18:0-2OH) acids. Significant variability in fatty acid composition was detected among castor accessions. Ricinoleic acid (RA) was positively correlated with dihydroxystearic acid (DHSA) but highly negatively correlated with the five other fatty acids except linolenic acid. The results for oil content and fatty acid composition obtained from this study will be useful for end-users to explore castor germplasm for biodiesel production.     

Synthesis of structured lipids via acidolysis of docosahexaenoic acid single cell oil (DHASCO) with capric acid

Screening of five commercially available lipases for the incorporation of capric acid (CA) into docosahexaenoic acid single cell oil (DHASCO) indicated that lipase PS-30 from Pseudomonas sp. was most effective. Of the various reaction parameters examined, namely, the mole ratio of substrates, enzyme amount, time of incubation, reaction temperature, and amount of added water, for CA incorporation into DHASCO, the optimum conditions were a mole ratio of 1:3 (DHASCO/CA) at a temperature of 45 degrees C, and a reaction time of 24 h in the presence of 4% enzyme and 2% water content. Examination of the positional distribution of fatty acids on the glycerol backbone of the modified DHASCO with CA showed that CA was present mainly in the sn-1,3 positions of the triacylglycerol (TAG) molecules. Meanwhile, DHA was favorably present in the sn-2 position, but also located in the sn-1 and sn-3 positions. The oxidative stability of the modified DHASCO in comparison with the original DHASCO, as indicated in the conjugated diene values, showed that the unmodified oil remained relatively unchanged during storage for 72 h, but DHASCO-based structured lipid was oxidized to a much higher level than the original oil. The modified oil also attained a considerably higher thiobarbituric acid reactive substances value than the original oil over the entire storage period. However, when the oil was subjected to the same process steps in the absence of any enzyme, there was no significant difference (p > 0.05) in its oxidative stability when compared with enzymatically modified DHASCO. Therefore, removal of antioxidants during the process is primarily responsible for the compromised stability of the modified oil.     

Stearidonic acid soybean oil enriched with palmitic acid at the sn-2 position by enzymatic interesterification for use as human milk fat analogues

Stearidonic acid (SDA, C18:4n-3) enriched soybean oil may be added to the diet to increase intake of omega-3 fatty acids (FAs). Human milk fat has ≥60% of palmitic acid (PA), by weight, esterified at the sn-2 position to improve absorption of fat and calcium in infants. Enzymatic interesterification of SDA soybean oil and tripalmitin produced structured lipids (SLs) enriched with PA at the sn-2 position of the triacylglycerol. Reactions were catalyzed by Novozym 435 or Lipozyme TL IM under various conditions of time, temperature, and substrate mole ratio. Response surface methodology was used to design the experiments. Model optimization conditions were predicted to be 1:2 substrate mole ratio at 50 °C for 18 h with 10% (by weight) Lipozyme TL IM resulting in 6.82 ± 1.87% total SDA and 67.19 ± 9.59% PA at sn-2; 1:2 substrate mole ratio at 50 °C for 15.6 h resulting in 8.01 ± 2.41% total SDA and 64.43 ± 13.69% PA at sn-2 with 10% (by weight) Novozym 435 as the biocatalyst. The SLs may be useful as human milk fat analogues for infant formula formulation with health benefits of the omega-3 FAs.     

Enzymatic interesterification of butterfat with rapeseed oil in a continuous packed bed reactor

Lipase-catalyzed interesterification of butterfat blended with rapeseed oil (70/30, w/w) was investigated both in batch and in continuous reactions. Six commercially available immobilized lipases were screened in batch experiments, and the lipases, Lipozyme TL IM and Lipozyme RM IM, were chosen for further studies in a continuous packed bed reactor. TL IM gave a fast reaction and had almost reached equilibrium with a residence time of 30 min, whereas RM IM required 60 min. The effect of reaction temperature was more pronounced for RM IM. TL IM showed little effect on the interesterification degree when the temperature was raised from 60 degrees C to 90 degrees C, whereas RM IM had a positive effect when the temperature was increased from 40 degrees C to 80 degrees C. Even though TL IM is an sn-1,3 specific lipase, small changes in the sn-2 position of the triacylglycerol could be seen. The tendency was toward a reduction of the saturated fatty acid C14:0 and C16:0 and an increase of the long-chain saturated and unsaturated fatty acids (C18:0 and C18:1), especially at longer residence times (90 min). In prolonged continuous operation the activity of TL IM was high for the first 5 days, whereafter it dramatically decreased over the next 10 days to an activity level of 40%. In general, the study shows no significant difference for butterfat interesterification in terms of enzyme behavior from normal vegetable oils and fats even though it contains short-chain fatty acids and cholesterol. However, the release of short-chain fatty acids from enzymatic reactions makes the sensory quality unacceptable for direct edible applications.     

Synthesis of structured lipids containing medium-chain and omega-3 fatty acids

The ability of different lipases to incorporate omega3 fatty acids, namely, eicosapentaenoic acid (EPA, C20:5n-3), docosapentaenoic acid (DPA, C22:5n-3), and docosahexaenoic acid (DHA, C22:6n-3), into a high-laurate canola oil, known as Laurical 35, was studied. Lipases from Mucor miehei (Lipozyme-IM), Pseudomonas sp. (PS-30), and Candida rugosa (AY-30) catalyzed optimum incorporation of EPA, DPA, and DHA into Laurical 35, respectively. Other lipases used were Candida anatrctica (Novozyme-435) and Aspergillus niger (AP-12). Response surface methodology (RSM) was used to obtain a maximum incorporation of EPA, DPA, and DHA into high-laurate canola oil. The process variables studied were the amount of enzyme (2-6%), reaction temperature (35-55 degrees C), and incubation time (12-36 h). The amount of water added and mole ratio of substrates (oil to n-3 fatty acids) were kept at 2% and 1:3, respectively. The maximum incorporation of EPA (62.2%) into Laurical 35 was predicted at 4.36% of enzyme load and 43.2 degrees C over 23.9 h. Under optimum conditions (5.41% enzyme; 38.7 degrees C; 33.5 h), the incorporation of DPA into high-laurate canola oil was 50.8%. The corresponding maximum incorporation of DHA (34.1%) into Laurical 35 was obtained using 5.25% enzyme, at 43.7 degrees C, over 44.7 h. Thus, the number of double bonds and the chain length of fatty acids had a marked effect on the incorporation omega3 fatty acids into Laurical 35. EPA and DHA were mainly esterified to the sn-1,3 positions of the modified oils, whereas DPA was randomly distributed over the three positions of the triacylglycerol molecules. Meanwhile, lauric acid remained esterified mainly to the sn-1 and sn-3 positions of the modified oils. Enzymatically modified Laurical 35 with EPA, DPA, or DHA had higher conjugated diene (CD) and thiobarbituric acid reactive substance (TBARS) values than their unmodified counterpart. Thus, enzymatically modified oils were more susceptible to oxidation than their unmodified counterparts, when both CD and TBARS values were considered.     

Synthesis of structured triacylglycerols by lipase-catalyzed acidolysis in a packed bed bioreactor

Structured triacylglycerols (ST) from canola oil were produced by enzymatic acidolysis in a packed bed bioreactor. A commercially immobilized 1,3-specific lipase, Lipozyme IM, from Rhizomucormiehei, was the biocatalyst and caprylic acid the acyl donor. Parameters such as substrate flow rate, substrate molar ratio, reaction temperature, and substrate water content were examined. High-performance liquid chromatography was used to monitor the reaction and product yields. The study showed that all of the parameters had effects on the yields of the expected di-incorporated (dicaprylic) ST products. Flow rates below 1 mL/min led to reaction equilibrium, and lower flow rates did not raise the incorporation of caprylic acid and the product yield. Incorporation of caprylic acid and the targeted di-incorporated ST was increased by approximately 20% with temperature increase from 40 to 70 degrees C. Increasing the substrate molar ratio from 1:1 to 7:1 increased the incorporation of caprylic acid and the product yield slightly. Water content in the substrate also had a mild influence on the reaction. Water content at 0.08% added to the substrate gave the lowest incorporation and product yield. The use of solvent in the medium was also studied, and results demonstrated that it did not increase the reaction rate at 55 degrees C when 33% hexane (v/v) was added. The main fatty acids at the sn-2 position of the ST were C(18:1), 54. 7 mol %; C(18:2), 30.7 mol %; and C(18:3), 11.0 mol %.     

HPLC separation and NMR structural elucidation of sn-1,2-, 2,3-, and 1,3-diacylglycerols from olive oil as naphthylethylurethane derivatives

In this study, sn-1,2-, sn-2,3-, and sn-1,3-diacylglycerols were isolated from olive oil, and their urethane derivatives (urethanes) were prepared. Normal-phase high-performance liquid chromatography (NP-HPLC) separation of the urethane isomers was performed and the separate classes were studied by nuclear magnetic resonance (NMR). The use of 1H NMR and homo- and heteronuclear 2D techniques provided a great amount of information in a very short time, particularly when a high-field NMR instrument (700 MHz) was used. Particularly diagnostic for this kind of compound was the glyceridic moiety that presents typical chemical shifts both for carbon and hydrogen. These studies show the usefulness of NMR spectroscopy to recognize clearly the sn-1,3- and, moreover, sn-1,2- with respect to sn-2,3-diacylglycerols, although very minor differences occur between them.     

Changes in the concentrations of free fatty acid, monoacylglycerol, and diacylglycerol in the subcutaneous fat of Iberian ham during the dry-curing process

Changes in diacylglycerols, monoacylglycerols, and free fatty acid composition of subcutaneous fat of six Iberian hams during the dry-cured process were investigated. In addition, an analytical method for simultaneous quantification of diacylglycerols, monoacylglycerols, and free fatty acid by solid-phase extraction-gas chromatography was developed. The different molecular species of free fatty acids, monoacylglycerols, and diacylglycerols and 1,2- and 1,3-isomers of diacylglycerols have been described for the first time in this type of sample. A logarithmic increase of the 1,3-diacylglycerol profile throughout the processing time has been found, reaching a balance value of 62% around 500 days. The formation of diacylglycerol isomers takes place, although the 1,3-/1,2-diacylglycerol ratio increases during the process to 1.65 due to isomerization of the 1,2-form toward the 1,3-form. The profiles of monoacyl- and diacylglycerols and free fatty acids follow the same trend. The experimental values of free fatty acid are greater than theoretical prediction, probably due to phospholipid and monoacylglycerol hydrolysis.     

(13)C NMR characterization of triacylglycerols of Moringa oleifera seed oil: an "oleic-vaccenic acid" oil

The composition of acyl chains and their positions in the triacylglycerols of the oil extracted from seeds of Moringa oleifera were studied by (13)C NMR spectroscopy. The unsaturated chains of M. oleifera seed oil were found to comprise only mono-unsaturated fatty acids and, in particular, two omega-9 mono-unsaturated acids, (cis-9-octadecenoic (oleic acid) and cis-11-eicosenoic acids) and one omega-7 mono-unsaturated acid (cis-11-octadecenoic acid (vaccenic acid)). The mono-unsaturated fatty acids were detected as separated resonances in the spectral regions where the carbonyl and olefinic carbons resonate according to the 1,3- and 2-positions on the glycerol backbone. The unambiguous detection of vaccenic acid was also achieved through the resonance of the omega-3 carbon. The (13)C NMR methodology enabled the simultaneous detection of oleate, vaccenate, and eicosenoate chains according to their positions on the glycerol backbone (1,3- and 2-positions) through the carboxyl, olefinic, and methylene envelope carbons of the triacylglycerol acyl chains.     

Molecular species of acylglycerols incorporating radiolabeled fatty acids from castor (Ricinus communis L.) microsomal incubations

Sixty-one molecular species of triacylglycerols (TAG) and diacylglycerols produced from castor microsomal incubations incorporating six different (14)C-labeled fatty acids have been identified and quantified. The preference for incorporation into TAG was in the order ricinoleate > oleate > linoleate > linolenate > stearate > palmitate. Ricinoleate was the major fatty acid incorporated, whereas stearate, linolenate, and palmitate were incorporated at low levels. Twenty-one molecular species of acylglycerols (HPLC peaks) in castor oil have also been assigned. The levels of TAG in castor oil are RRR (triricinolein) > RR-TAG > R-TAG > no R-TAG. The levels of the molecular species within the groups of RR-TAG, RL-TAG, and LL-TAG individually are ricinoleate > linoleate > oleate > linolenate, stearate, and palmitate. The results of the labeled fatty acid incorporation are consistent with ricinoleate being preferentially driven into TAG and oleate being converted to ricinoleate in castor oil biosynthesis.     

Positional distribution of conjugated linoleic acid in triacylglycerol of Saccharomyces cerevisiae

Saccharomyces cerevisiae was cultivated in the presence of cis-9,trans-11 or trans-10,cis-12 isomers of free conjugated linoleic acid (CLA), and the effects of the isomers on the regioisomerisms of triacylglycerol (TAG) of the yeast were elucidated. Both isomers constituted about 34% of all fatty acids and increased drastically the number of different TAG species. Nearly all of the species contained CLA in at least one sn-position. In the most abundant species analyzed (20% of total species), the cis-9,trans-11 isomer appeared in combination with monounsaturated fatty acids (C16:1, C:18:1) whereas trans-10,cis-12 isomer was most frequently present with a medium chain fatty acid (C10:0 or C12:0) in the sn-2 position and C16:0 in one of the end positions (14% of total species). With either isomer, the amount of TAG species in which CLA encompassed all sn-positions was ca. 4%. Thus, S. cerevisiae can be used to produce edible single cell oil characterized by very heterogeneous distribution of CLA among the different TAG species.