Improvement of polyunsaturated fatty acids synthesis by the coexpression of CYB5 with desaturase genes in Saccharomyces cerevisiae

Since Saccharomyces cerevisiae contains Δ9 fatty acid desaturase (OLE1) as a sole fatty acid desaturase, it produces saturated and monounsaturated fatty acids of 16- and 18-carbon compounds. We showed earlier that Kluyveromyces lactis Δ12 (KlFAD2) and ω3 (KlFAD3) fatty acid desaturase genes enabled S. cerevisiae to make also polyunsaturated fatty acids (PUFAs), linoleic (18:2n-6), and α-linolenic (18:3n-3) acids. Unlike Δ9 fatty acid desaturase Ole1p, the two added fatty acid desaturases (KlFAD2and KlFAD3) do not contain a cytochrome b5 domain, and we now report on effects of the overexpression of K. lactis and S. cerevisiae cytochrome b5 (CYB5) genes as well as temperature effects on PUFA synthesis. Without extra cytochrome b5, while PUFA synthesis is significant at low temperature (20 °C), it was marginal at 30 °C. Overexpression of cytochrome b5 at 20 °C did not affect the fatty acid synthesis so much, but it significantly enhanced the synthesis of PUFA at 30 °C.     

Isolation of a novel C18-Δ9 polyunsaturated fatty acid specific elongase gene from DHA-producing <Emphasis Type="Italic">Isochrysis galbana</Emphasis> H29 and its use for the reconstitution of the alternative Δ8 pathway in <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

A novel gene (IgASE2) encoding a C18-Δ9 polyunsaturated fatty acids specific (C18-Δ9-PUFAs-specific) elongase was isolated and characterized from DHA-rich microalga, Isochrysis galbana H29. The IgASE2 gene was 1,653 bp in length, contained a 786 bp ORF encoding a protein of 261 amino acids that shared 87% identity with Δ9 elongase, IgASE1, and possessed a 44 bp 5′-untranslated region (5′-UTR) and a 823 bp 3′-untranslated region (3′-UTR). IgASE2, by its heterologous expression in Saccharomyces cerevisiae, elongated linoleic acid (LA, 18:2n−6) and α-linolenic (ALA, 18:3n−3) to eicosadienoic acid (EDA, 20:2n−6) and eicosatrienoic acid (ETrA, 20:3n−3), respectively. The conversions of LA to EDA and ALA to ETrA were 57.6 and 56.1%, respectively. Co-expression of this elongase with Δ8 desaturase required for the synthesis of C20-polyunsaturated fatty acids resulted in the accumulation of dihomo-γ-linolenic acid (20:3n−6) from LA and eicosatetraenoic acid (20:4n−6) from ALA. These results demonstrated that IgASE2 exhibited C18-Δ9-PUFAs-specific elongase activity and the alternative Δ8 pathway was reconstituted.     

Co-expression of the borage Δ6 desaturase and the Arabidopsis Δ15 desaturase results in high accumulation of stearidonic acid in the seeds of transgenic soybean

Two relatively rare fatty acids, γ-linolenic acid (GLA) and stearidonic acid (STA), have attracted much interest due to their nutraceutical and pharmaceutical potential. STA, in particular, has been considered a valuable alternative source for omega-3 fatty acids due to its enhanced conversion efficiency in animals to eicosapentaenoic acid when compared with the more widely consumed omega-3 fatty acid, α-linolenic acid (ALA), present in most vegetable oils. Exploiting the wealth of information currently available on in planta oil biosynthesis and coupling this information with the tool of genetic engineering it is now feasible to deliberately perturb fatty acid pools to generate unique oils in commodity crops. In an attempt to maximize the STA content of soybean oil, a borage Δ⁶ desaturase and an Arabidopsis Δ¹⁵ desaturase were pyramided by either sexual crossing of transgenic events, re-transformation of a Δ⁶ desaturase event with the Δ¹⁵ desaturase or co-transformation of both desaturases. Expression of both desaturases in this study was under the control of the seed-specific soybean β-conglycinin promoter. Soybean events that carried only the Δ¹⁵ desaturase possessed a significant elevation of ALA content, while events with both desaturases displayed a relative STA abundance greater than 29%, creating a soybean with omega-3 fatty acids representing over 60% of the fatty acid profile. Analyses of the membrane lipids in a subset of the transgenic events suggest that soybean seeds compensate for enhanced production of polyunsaturated fatty acids by increasing the relative content of palmitic acid in phosphatidylcholine and other phospholipids.     

The fatty acid profile of vegetative Azotobacter vinelandii ATCC 12837: growth phase-dependence

Fatty acids of Azotobacter vinelandii ATCC 12837 were determined at various times during aerobic vegetative growth at 30°C to provide baseline data for studying the effects of chemical agents on the organism’s survival and fatty acid biosynthesis. Palmitate (16:0) was the highest at 36.7±4.3 mol% (mean±SD) after the first 5 h in fresh culture, decreasing slightly to 33.4±2.6 mol% at 49 h. The other fatty acids were therefore each normalized as a ratio of 16:0. At 5 h, as a ratio of 16:0, myristate (14:0) was 0.14±0.06, palmitoleate (16:1cΔ^9–10) 0.13±0.06, oleate (18:1cΔ^9–10) 0.21±0.12, cis-vaccenate (18:1cΔ^11–12) 0.30±0.17 and stearate (18:0) 0.68±0.02. As the growth phase advanced to 49 h, 14:0 and 16:1cΔ^9–10 increased, 18:1cΔ^9–10 decreased and cis-vaccenate reciprocally increased, whereas 18:0 decreased. These suggest that the saturated fatty acid biosynthesis pathway yielded 16:0 and 18:0 in the 5-h lag period. By desaturation, 18:0 formed the unsaturated fatty acid (UFA) 18:1cΔ^9–10. As the culture aged, the anaerobic UFA biosynthesis pathway formed 16:1cΔ^9–10, which was elongated to 18:1cΔ^11–12. These fatty acid alterations represent a homeoviscous adaptation, modulating the microbe’s membrane lipid viscosity for optimal cellular function.     

Identification of Δ9-elongation activity from <Emphasis Type="Italic">Thraustochytrium aureum</Emphasis> by heterologous expression in <Emphasis Type="Italic">Pichia pastoris</Emphasis>

The Δ9-elongase isolated from Thraustochytrium aureum, which contains a high level of polyunsaturated fatty acids (PUFAs), was demonstrated to be associated with the synthesis of C20 PUFAs. The TaELO gene contains a 825 bp ORF that encodes a protein of 274 amino acids that shares a high similarity with other PUFA elongases. The expression of the TaELO gene in Pichia pastoris resulted in the elongation of linoleic acid (LA, C18:2; n-6) and α-linolenic acid (ALA, C18:3; n-3) to eicosadienoic acid (EDA, C20:2; n-6) and eicosatrienoic acid (ETrA, C20:3; n-3), respectively. The endogenous conversion rate of LA and ALA to EDA and ETrA was 32.68 and 38.57%, respectively. In addition, TaELO was also able to synthesize eicosenoic acid (C20:1; n-9) from oleic acid (OA, C18:1; n-9), even though the conversion level was low (2.81%). Furthermore, TaELO was able to carry out the 6Δ-elongation of γ-linolenic acid (GLA, C18:3; n-6) to dihomo-γ-linolenic acid (DGLA, C20:3; n-6) and Δ5-elongation of eicosapentaenoic acid (EPA, C20:5; n-3) to docosapentaenoic acid (DPA, C22:5; n-3). The conversion rate of GLA to DGLA and EPA to DPA were 93 and 28.36%, respectively. The TaELO protein was confirmed to have multifunctional activities, such as Δ9, Δ6, and Δ5-elongations as well as the elongation of monounsaturated fatty acid.     

Isolation and functional characterization of polyunsaturated fatty acid elongase (AsELOVL5) gene from black seabream (Acanthopagrus schlegelii)

To identify the genes encoding fatty acid elongases for the biosynthesis of polyunsaturated fatty acids (PUFAs), we isolated a cDNA via degenerate PCR and RACE-PCR from Acanthopagrus schlegelii with a high similarity to the ELOVL5-like elongases of mammals and fishes. This gene is termed AsELOVL5 and encodes a 294 amino acid protein. When AsELOVL5 was expressed in Saccharomyces cerevisiae, it conferred an ability to elongate γ-linolenic acid (18:3 n−6) to di-homo-γ-linolenic acid (20:3 n−6). In addition, the transformed cells converted arachidonic acid (20:4 n−6) and eicosapentaenpic acid (20:5 n−3) to docosatetraenoic acid (22:4 n−6) and docosapentaenoic acid (22:5 n−3), respectively. These results indicate that the AsELOVL5 gene encodes a long-chain fatty acid elongase capable of elongating C₁₈Δ6/C₂₀Δ5 but not C₂₂ PUFA substrates.     

Identification of Primula “front-end” desaturases with distinct n−6 or n−3 substrate preferences

cDNA clones encoding cytochrome b₅ fusion desaturases were isolated from Primula cortusoides L. and Primula luteola Ruprecht, species previously shown to preferentially accumulate either n−6 or n−3 Δ6-desaturated fatty acids, respectively. Functional characterisation of these desaturases in yeast revealed that the recombinant Primula enzymes displayed substrate preferences, resulting in the predominant synthesis of either γ-linolenic acid (n−6) or stearidonic acid (n−3). Independent expression of the two Primula desaturases in transgenic Arabidopsis thaliana confirmed these results, with γ-linolenic acid and stearidonic acid accumulating in both leaf and seed tissues to different levels, depending on the substrate specificity of the desaturase. Targeted lipid analysis of transgenic Arabidopsis lines revealed the presence of Δ6-desaturated fatty acids in the acyl-CoA pools of leaf but not seed tissue. The implications for the transgenic synthesis of C₂₀ polyunsaturated fatty acids via the elongation of Δ6-desaturated fatty acids are discussed, as is the potential of using Primula desaturases in the synthesis of C₁₈ n−3 polyunsaturated fatty acids such as stearidonic acid.     

Δ<Superscript>6</Superscript>-Desaturase from <Emphasis Type="Italic">Mortierella alpina</Emphasis>: cDNA cloning,expression, and phylogenetic analysis

The open reading frame of the Δ⁶-desaturase gene was isolated from Mortierella alpina W15 and the gene was cloned into a pPIC3.5K vector. The vector was transformed into Pichia pastoris GS115 and expression was induced with methanol. The Δ⁶-desaturase expressed in P. pastoris GS115 catalyzed the conversion of linoleic acid to γ-linolenic acid but not the conversion of α-linolenic acid to octadecatetraenoic acid. The results indicate that the Δ⁶-desaturase gene from M. alpina W15 has substrate specificity in different organisms. Phylogenetic analysis revealed that Δ⁶-desaturase genes can be divided into four monophyletic groups. This work paves the way for further study of the functions of Δ⁶-desaturase in fatty acid metabolism and its three-dimensional structure.     

Isolation and Characterisation of a High-Efficiency Desaturase and Elongases from Microalgae for Transgenic LC-PUFA Production

The production of long-chain polyunsaturated fatty acids from precursor molecules linoleic acid (LA; 18:2ω6) and α-linolenic acid (ALA; 18:3ω3) is catalysed by sequential desaturase and elongase reactions. We report the isolation of a front-end Δ6-desaturase gene from the microalgae Ostreococcus lucimarinus and two elongase genes, a Δ6-elongase and a Δ5-elongase, from the microalga Pyramimonas cordata. These enzymes efficiently convert their respective substrates when transformed in yeast (39–75% conversion for ω3 substrate fatty acids), and the Δ5-elongase in particular displays higher elongation efficiency (75% for conversion of eicosapentaenoic acid (20:5ω3) to docosapentaenoic acid (22:5ω3)) than previously reported genes. In addition, the Δ6-desaturase is homologous with acyl-CoA desaturases and shows a strong preference for the ω3 substrate ALA.     

Transgenic expression of a Δ12-epoxygenase gene in Arabidopsis seeds inhibits accumulation of linoleic acid

The Crepis palaestina cDNA Cpal2 encodes a Δ12-epoxygenase that can catalyse the synthesis of 12,13-epoxy-cis-9-octadecenoic acid (18:1E) from linoleic acid (18:2). When the Cpal2 gene was expressed under the control of the napin seed-specific promoter in Arabidopsis thaliana (L.) Heynh., the seed lipids accumulated only low levels of 18:1E and also 12,13-epoxy-cis-9,15-octadec-2-enoic acid (18:2E). Despite the fact that the levels of these epoxy fatty acids comprised only up to 6.2% of the total fatty acids, there was a very marked increase in oleic acid (18:1) and decrease in linoleic (18:2) and α-linolenic (18:3) acids in these plants, indicating that endogenous Δ12-desaturation was greatly reduced in these plants. Significant between-line differences in the levels of Cpal2 mRNA were observed during seed development, but were not associated with any major variation in mRNA levels for the endogenous ArabidopsisΔ12-desaturase (Fad2). This suggests that if an unfavourable interaction occurs between the transgenic Δ12-epoxygenase and the endogenous Δ12-desaturase, which decreases the level of desaturation, it occurs at either the translational or post-translational level. We further show that the co-expression of a Δ12-desaturase gene from C. palaestina in Cpal2 transgenic Arabidopsis returns the relative proportions of the C18 seed fatty acids to normal levels and results in an almost twofold increase in total epoxy fatty acids. Received: 11 August 2000 / Accepted: 7 September 2000     

Agrobacterium-mediated Transformation of Brassica juncea with a Cyanobacterial (Synechocystis PCC6803) Delta-6 Desaturase Gene Leads to Production of Gamma-linolenic Acid

Genetic manipulation of the oil-yielding crop plants for better oil quality through biotechnological methods is an important aspect of crop improvement. Due to the inherent absence of the Δ⁶-desaturase (d6D) function, Brassica juncea, an oil-yielding crop plant, is unable to synthesize γ-linolenic acid (GLA), a nutritionally important fatty acid although the crop plant synthesizes the precursor fatty acids required for GLA production. Cyanobacterial d6D introduces carbon–carbon double bond onto linoleic acid (C18:2) and α-linolenic acid (C18:3) by desaturation processes for production of GLA and octadecatetraenoic acid (OTA) respectively. In the present investigation, d6D coding sequence from Synechocystis sp. PCC6803 was cloned by polymerase chain reaction and introduced into B. juncea through Agrobacterium-mediated transformation technique. Both cytosolic as well as seed-specific expression of d6D were attempted. The transformed plants show production of GLA and OTA in contrast to their absence in the untransformed control plants adducing evidence for introgression and functional expression of the cyanobacterial d6D gene in B. juncea.     

Fatty-acid composition of polar lipids in fruit and leaf chloroplasts of “16:3”- and “18:3”-plant species

The fatty-acid composition of polar lipids from fruit and leaf chloroplasts was compared in five Solanaceous and two cucurbit species. The acylated fatty acids in monogalactosyl diglycerides (MGDG) from leaf chloroplasts of all five Solanaceous species included substantial amounts of ^7,10,13-hexadecatrienoic acid (16:3). In contrast, the MGDG from fruit chloroplasts of the Solanaceae contained very little of this plastid-specific polyunsaturate, and instead included a proportionately greater percentage of linoleic acid (18:2). In MGDG from leaf chloroplasts of two cucurbits, -linolenic acid (18:3) constituted 94–95% of the acylated fatty acids. Fruit-chloroplast galactolipids of the cucurbits had a greater abundance of 18:2, and hence a higher 18:2/18:3 ratio, than found in the corresponding leaf lipids. Among the phosphoglycerides, the unusual fatty acid 3-trans-hexadecenoate (trans-16:1) constituted from 15 to 24% of the acylated fatty acids in phosphatidyl glycerol (PG) from leaf chloroplasts (all species). In sharp contrast, trans-16:1 was virtually absent in PG from fruit chloroplasts of both Solanaceous and cucurbit species, and was replaced by a proportionate increase in the content of palmitate (16:0). The observed differences in the polar lipid fatty-acid composition of fruit and leaf chloroplasts are discussed in terms of the relative activity of several intrachloroplastic enzymes involved in lipid synthesis and fatty-acyl desaturation.Abbreviations MGDG monogalactosyldiglyceride - DGDG digalactosyl diglyceride - PC phosphatidyl choline - PE phosphatidyl ethanolamine - PG phosphatidyl glycerol     

Disruption of the Fatty Acid Δ<Superscript>6</Superscript>-Desaturase Gene in the Oil-Producing Fungus <Emphasis Type="Italic">Mortierella isabellina</Emphasis> by Homologous Recombination

The γ-linolenic acid-producing fungus Mortierella isabellina 6-22 is an important industrial strain. To clarify the biosynthetic pathways for polyunsaturated fatty acids in this strain, a disruption vector pD4MI6, including 5′ and 3′ regions of the fatty acid Δ⁶-desaturase open reading frame as homologous recombination elements and the Escherichia coli hygromycin B (HmB) phosphotransferase gene (hph) as selectable marker, was successfully constructed. Following transformation of pD4MI6 into the hygromycin B-sensitive recipient strain M. isabellina 6-22-4, a Δ⁶-desaturase gene-defective mutant strain was selected that was unable to produce γ-linolenic acid as determined by gas chromatography and molecular analysis. The morphology and physiology of the mutant, such as colony shape, color, and growth rate, were changed dramatically compared with that of strain M. isabellina 6-22-4.     

Cloning and identification of a novel C18-Δ9 polyunsaturated fatty acid specific elongase gene from DHA-producing <Emphasis Type="Italic">Isochrysis galbana</Emphasis> H29

Isochrysis galbana, a marine prymnesiophyte microalga, is able to produce a high level of long chain polyunsaturated fatty acids such as docosahexaenoic acid (DHA, C22:6n-3). In this article, a novel gene (IgASE2) that encoded a C18-Δ9 polyunsaturase fatty acids specific (C18-Δ9-PUFAs-specific) elongase was isolated and characterized from DHA-rich microalga, I. galbana H29. A full-length cDNA of 1653 bp was cloned by rapidamplification of cDNA ends (RACE) PCR techniques. The IgASE2 contained a 786 bp ORF encoding a protein of 261 amino acids that shared 87% identity with the reported Δ9-elongase IgASE1, a 44 bp 5′ untranslated region and an 823 bp 3′ untranslated region. The function of IgASE2 was demonstrated by its heterologous expression in Saccharomyces cerevisiae. In S. cerevisiae, IgASE2 elongated linoleic acid (LA, C18:2n-6), α-linolenic (ALA, C18:3n-3) to eicosadienoic acid (EDA, C20:2n-6) and eicosatrienoic acid (ETrA, C20:3n-3). The conversion ratios of LA to EDA and ALA to ETrA were 60.47 and 58.36%, respectively. However, IgASE2 could not catalyze the elongation reactions of oleic acid (OA, C18:1n-9) and other fatty acids. These results confirmed that IgASE2 had C18-Δ9-PUFAs-specific elongase activity.     

Activities of liver microsomal fatty acid desaturases in zinc-deficient rats force-fed diets with a coconut oil/safflower oil mixture of linseed oil

The present study was conducted to investigate the effect of zinc deficiency on fatty acid desaturation in rats fed two different types of dietary fat, a mixture of coconut oil and safflower oil (7∶1, w/w, “coconut oil diet”) or linseed oil (“linseed oil diet”). In order to ensure an adequate food intake, all rats were force-fed by gastric tube. Zinc deficiency caused statistical significant reducion of Δ9-desaturase activity in liver microsomes of rats fed coconut oil diet and tendencial reduction (p<0.15) in rats fed linseed oil diet compared with control rats fed diets with the same type of fat. In agreement with this effect, zinc deficiency in the rats fed both types of dietary fat increased the ratio between total saturated and total monounsaturated fatty in liver phospholipids and liver microsomes. Zinc deficient rats on the coconut oil diet had unchanged Δ6-desaturase activity with linoleic acid as substrate and lowered activity with α-linolenic acid as substrate. In contrast, zinc deficient rats on the linseed oil diet had increased Δ6-desaturase activity with linoleic acid as substrate and unchanged activity with α-linolenic acid. Because linoleic acid is the main substrate for Δ6-desaturase in the rats fed coconut oil diet, and α-linolenic acid is the main substrate in the rats fed linseed oil diet, it is concluded that in vivo Δ6-desaturation was not changed by zinc deficiency in the rats fed both types of dietary fat. Activity of Δ5-desaturase was also not changed by zinc deficiency in the rats fed both dietary fats. Levels of fatty acids in liver phospholipids and microsomes derived by Δ4-, Δ5-, and Δ6-desaturation were not consistently changed by zinc deficiency in the rats fed both types of dietary fat. Thus, the enzyme studies and also fatty acid composition data of liver phospholipids and microsomes indicate that zinc deficiency does not considerably disturb desaturation of linoleic and α-linolenic acid. Therefore, it is suggested that similarities between deficiencies of zinc and essential fatty acids described in literature are not due to disturbed desaturation of linoleic acid in zinc deficiency. The present study also indicates that zinc deficiency enhances incorporation of eicosapentaenoic acid into phosphatidylcholine of rats fed diets with large amounts ofn-3 polyunsaturated fatty acids.     

Chemotaxonomic differentiation of conifer families and genera based on the seed oil fatty acid compositions: multivariate analyses

 The fatty acid compositions of seed oils from 34 conifer species, mainly Pinaceae and secondarily Cupressaceae, have been determined by gas-liquid chromatography of the methyl esters. As noted in earlier studies, these oils were characterized by the presence of several Δ5-olefinic acids, i.e., 5,9-18:2, 5,9,12-18:3, 5,9,12,15-18:4, 5,11-20:2, 5,11,14-20:3, and 5,11,14,17-20:4 acids, in addition to the more common saturated, oleic, linoleic and α-linolenic acids. Based on these fatty acid compositions, and on those established in earlier systematic studies (totalling 82 species), we established a chemotaxonomic grouping of the main conifer families, i.e., of the Pinaceae, Taxodiaceae, Cupressaceae, and Taxaceae. This was achieved using multivariate analyses (principal component analysis and discriminant analysis). The fatty acids that discriminate best in this classification are the 5,11,14,17-20:4, 9,12,15-18:3 and 5,9,12-18:3 acids. Moreover, it was possible to differentiate between several genera of the Pinaceae: Pinus (including Tsuga and Pseudotsuga), Abies, Cedrus, and Picea plus Larix, represented quite distinct groups. Other fatty acids such as oleic, linoleic, and 5,9-18:2 acids were also important for this purpose. The fatty acid compositions, and particularly the Δ5-olefinic acid contents of conifer seed oils, may thus be applied to the chemosystematic distinction among conifer families as well as genera of the Pinaceae. Received: 3 January 1997 / Accepted: 17 April 1997     

Functional characterization of a delta 6-desaturase gene from the black seabream (<Emphasis Type="Italic">Acanthopagrus schlegeli</Emphasis>)

Delta 6-fatty acid desaturase (D6DES) is used in the synthesis of polyunsaturated fatty acids (PUFAs) from microorganisms to higher animals, including arachidonic acid (ARA) and eicosapentaenoic acid (EPA). A 1,338 bp full-length cDNA encoding D6DES was cloned from Acanthopagrus schlegeli (AsD6DES) through degenerate- and RACE-PCR methods. A recombinant vector expressing AsD6DES (pYES-AsD6DES) was subsequently constructed and transformed into Saccharomyces cerevisiae to test the enzymatic activity of AsD6DES towards the production of n-6 and n-3 fatty acids. The exogenously expressed AsD6DES produced γ-linolenic acid (18:3 n-6) and stearidonic acid (18:4n-3) at 26 and 36% from exogenous linoleic acid (18:2n-6) and α-linolenic acid (18:3n-3), respectively, indicating that it is essentially a delta 6-fatty acid desaturase.     

Metabolic diversity in biohydrogenation of polyunsaturated fatty acids by lactic acid bacteria involving conjugated fatty acid production

Lactobacillus plantarum AKU 1009a effectively transforms linoleic acid to conjugated linoleic acids of cis-9,trans-11-octadecadienoic acid (18:2) and trans-9,trans-11–18:2. The transformation of various polyunsaturated fatty acids by washed cells of L. plantarum AKU 1009a was investigated. Besides linoleic acid, α-linolenic acid [cis-9,cis-12,cis-15-octadecatrienoic acid (18:3)], γ-linolenic acid (cis-6,cis-9,cis-12–18:3), columbinic acid (trans-5,cis-9,cis-12–18:3), and stearidonic acid [cis-6,cis-9,cis-12,cis-15-octadecatetraenoic acid (18:4)] were found to be transformed. The fatty acids transformed by the strain had the common structure of a C18 fatty acid with the cis-9,cis-12 diene system. Three major fatty acids were produced from α-linolenic acid, which were identified as cis-9,trans-11,cis-15–18:3, trans-9,trans-11,cis-15–18:3, and trans-10,cis-15–18:2. Four major fatty acids were produced from γ-linolenic acid, which were identified as cis-6,cis-9,trans-11–18:3, cis-6,trans-9,trans-11–18:3, cis-6,trans-10–18:2, and trans-10-octadecenoic acid. The strain transformed the cis-9,cis-12 diene system of C18 fatty acids into conjugated diene systems of cis-9,trans-11 and trans-9,trans-11. These conjugated dienes were further saturated into the trans-10 monoene system by the strain. The results provide valuable information for understanding the pathway of biohydrogenation by anaerobic bacteria and for establishing microbial processes for the practical production of conjugated fatty acids, especially those produced from α-linolenic acid and γ-linolenic acid. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.