Isolation of a novel strain of Butyrivibrio fibrisolvens that isomerizes linoleic acid to conjugated linoleic acid without hydrogenation, and its utilization as a probiotic for animals

Conjugated Linolenic Acid (CLnA) vs Conjugated Linoleic Acid (CLA): A Comprehensive Review of Potential Advantages in Molecular Characteristics, Health Benefits, and Production Techniques

Conjugated linoleic acid (CLA) has been extensively characterized due to its many biological activities and health benefits, but conjugated linolenic acid (CLnA) is still not well understood. However, CLnA has shown to be more effective than CLA as a potential functional food ingredient. Current research has not thoroughly investigated the differences and advantages between CLnA and CLA. This article compares CLnA and CLA based on molecular characteristics, including structural, chemical, and metabolic characteristics. Then, the in vivo research evidence of CLnA on various health benefits is comprehensively reviewed and compared with CLA in terms of effectiveness and mechanism. Furthermore, the potential of CLnA in production technology and product protection is analyzed. In general, CLnA and CLA have similar physicochemical properties of conjugated molecules and share many similarities in regulation effects and pathways of various health benefits as well as in the production methods. However, their specific properties, regulatory capabilities, and unique mechanisms are different. The superior potential of CLnA must be specified according to the practical application patterns of isomers. Future research should focus more on the advantageous characteristics of different isomers, especially the effectiveness and safety in clinical applications in order to truly exert the potential value of CLnA.

Impact of Probiotics on Dairy Production Efficiency

There has been growing interest on probiotics to enhance weight gain and disease resistance in young calves and to improve the milk yield in lactating animals by reducing the negative energy balance during the peak lactation period. While it has been well established that probiotics modulate the microbial community composition in the gastrointestinal tract, and a probiotic-mediated homeostasis in the rumen could improve feed conversation competence, volatile fatty acid production and nitrogen flow that enhances the milk composition as well as milk production, detailed changes on the molecular and metabolic level prompted by probiotic feed additives are still not understood. Moreover, as living biotherapeutic agents, probiotics have the potential to directly change the gene expression profile of animals by activating the signalling cascade in the host cells. Various direct and indirect components of probiotic approaches to improve the productivity of dairy animals are discussed in this review.

Isolation, characterization and conjugated linoleic acid production potential of bifidobacterial isolates from ruminal fluid samples of Murrah buffaloes

In the present study, we investigated the potential of Bifidobacterium spp., isolated from ruminal fluid samples from buffaloes (Bubalus bubalis) for conjugated linoleic acid (CLA) production. A total of 294 isolates were obtained from 86 ruminal fluid samples using Bifidus Selective Medium (BSM) medium, and based on phospoketolase assay, 24 isolates were presumptively confirmed to be Bifidobacterium species. Further, the isolates were confirmed morphologically, biochemically and by PCR assays for genus specific (16s rDNA) and transaldolase genes. All 24 strains were positive for conversion of linoleic acid (LA) to CLA by spectrophotometric screening. Gas chromatographic analysis showed that the strains produced cis9, trans11 and tran10, cis12 CLA isomers in LA-supplemented deMan-Rogosa-Sharpe (MRS) broth. The strains were identified as B. thermophilum (n = 21) and B. pseudolongum (n = 3) based on 16 rDNA sequence analysis. The study shows that Bifidobacterium spp., present in the rumens of buffaloes produce CLA from LA and the strains may have the potential to be used as probiotics to enhance the nutraceutical value of ruminant food products.

Microbial Production of Conjugated Linoleic Acid and Conjugated Linolenic Acid Relies on a Multienzymatic System

Conjugated linoleic acids (CLAs) and conjugated linolenic acids (CLNAs) have gained significant attention due to their anticarcinogenic and lipid/energy metabolism-modulatory effects. However, their concentration in foodstuffs is insufficient for any therapeutic application to be implemented. From a biotechnological standpoint, microbial production of these conjugated fatty acids (CFAs) has been explored as an alternative, and strains of the genera Propionibacterium, Lactobacillus, and Bifidobacterium have shown promising producing capacities. Current screening research works are generally based on direct analytical determination of production capacity (e.g., trial and error), representing an important bottleneck in these studies. This review aims to summarize the available information regarding identified genes and proteins involved in CLA/CLNA production by these groups of bacteria and, consequently, the possible enzymatic reactions behind such metabolic processes. Linoleate isomerase (LAI) was the first enzyme to be described to be involved in the microbiological transformation of linoleic acids (LAs) and linolenic acids (LNAs) into CFA isomers. Thus, the availability of lai gene sequences has allowed the development of genetic screening tools. Nevertheless, several studies have reported that LAIs have significant homology with myosin-cross-reactive antigen (MCRA) proteins, which are involved in the synthesis of hydroxy fatty acids, as shown by hydratase activity. Furthermore, it has been suggested that CLA and/or CLNA production results from a stress response performed by the activation of more than one gene in a multiple-step reaction. Studies on CFA biochemical pathways are essential to understand and characterize the metabolic mechanism behind this process, unraveling all the gene products that may be involved. As some of these bacteria have shown modulation of lipid metabolism in vivo, further research to be focused on this topic may help us to understand the role of the gut microbiota in human health.

Effect of Pufa Substrates on Fatty Acid Profile of Bifidobacterium breve Ncimb 702258 and CLA/CLNA Production in Commercial Semi-Skimmed Milk

Current research on lipids is highlighting their relevant role in metabolic/signaling pathways. Conjugated fatty acids (CFA), namely isomers of linoleic and linolenic acid (i.e. CLA and CLNA, respectively) can positively modulate inflammation processes and energy metabolism, promoting anti-carcinogenic and antioxidant effects, improved lipid profiles and insulin resistance, among others. Bioactive doses have been indicated to be above 1 g/d, yet these cannot be achieved through a moderate intake (i.e. 1-2 servings) of natural sources, and certain CLA-containing products have limited commercial availability. Such handicaps have fueled research interest in finding alternative fortification strategies. In recent years, screening of dairy products for CFA-producing bacteria has attracted much attention and has led to the identification of some promising strains, including Bifidobacterium breve NCIMB 702258. This strain has shown interesting producing capabilities in model systems as well as positive modulation of lipid metabolism activities in animal studies. Accordingly, the aim of this research work was to assay B. breve NCIMB 702258 in semi-skimmed milk to produce a probiotic fermented dairy product enriched in bioactive CLA and CLNA. The effect of substrates (LA, α-LNA and γ-LNA) on growth performance and membrane fatty acids profile was also studied, as these potential modifications have been associated to stress response. When tested in cys-MRS culture medium, LA, α-LNA and γ-LNA impaired the fatty acid synthesis by B. breve since membrane concentrations for stearic and oleic acids decreased. Variations in the C18:1 c11 and lactobacillic acid concentrations, may suggest that these substrates are also affecting the membrane fluidity. Bifidobacterium breve CFA production capacity was first assessed in cys-MRS with LA, α-LNA, γ-LNA or all substrates together at 0.5 mg/mL each. This strain did not produce CFA from γ-LNA, but converted 31.12% of LA and 68.20% of α-LNA into CLA and CLNA, respectively, after incubation for 24 h at 37 °C. In a second phase, B. breve was inoculated in a commercial semi-skimmed milk with LA, α-LNA or both at 0.5 mg/mL each. Bifidobacterium breve revealed a limited capacity to synthesize CLA isomers, but was able to produce 0.062-0.115 mg/mL CLNA after 24 h at 37 °C. However, organoleptic problems were reported which need to be addressed in future studies. These results show that although CFA were produced at too low concentrations to be able to achieve solely the bioactive dose in one daily portion size, fermented dairy products are a suitable vector to deliver B. breve NCIMB 702258.

Bacterial conjugated linoleic acid production and their applications

Conjugated linoleic acid (CLA) has been shown to exert various potential physiological properties including anti-carcinogenic, anti-obesity, anti-cardiovascular and anti-diabetic activities, and consequently has been considered as a promising food supplement. Bacterial biosynthesis of CLA is an attractive approach for commercial production due to its high isomer-selectivity and convenient purification process. Many bacterial species have been reported to convert free linoleic acid (LA) to CLA, hitherto only the precise CLA-producing mechanisms in Propionibacterium acnes and Lactobacillus plantarum have been illustrated completely, prompting the development of recombinant technology used in CLA production. The purpose of the article is to review the bacterial CLA producers as well as the recent progress on describing the mechanism of microbial CLA-production. Furthermore, the advances and potential in the heterologous expression of CLA genetic determinants will be presented.

Characterization of CLA-producing Butyrivibrio spp. reveals strain-specific variations

Conjugated Linoleic Acid (CLA), a fatty acid with high nutraceutical value is produced in rumen by resident bacterial species, especially Butyrivibrio spp. The present study was undertaken to examine the diversity of indigenous Butyrivibrio spp. from rumen liquor of Indian ruminants. The isolates were screened for their CLA production capability at different level of linoleic acid (LA) (0, 200, 400, 600, 800 μg/ml) at different time intervals (0, 2, 4, 6, 12, and 24 h). A total of more than 300 anaerobic cultures were isolated and 31 of them were identified as Butyrivibrio spp. based on morphological, biochemical and molecular characterization. Further, molecular characterization revealed that a large portion (67.7 %) of isolated Butyrivibrio belonged to Butyrivibrio fibrisolvens (B. fibrisolvens) species which is considered to be the most active bacteria amongst the rumen bacteria populace in terms of CLA production. Bacterial isolate VIII (strain 4a) showed highest CLA production ability (140.77 μg/ml) when incubated at 200 μg/ml LA for 2 h, which is 240 % higher than the isolate XXVII, Butyrivibrio proteoclasticus (B. proteoclasticus) showing lowest CLA production (57.28 μg/ml) amongst the screened isolates. It was evident from the observations recorded during the course of experiments that CLA production ability is strain specific and thus did not follow a single pattern. CLA production also varied with time of incubation and concentration of free linoleic acid supplemented in the growth medium. The results of these findings put forward a strain that is high CLA producer and can be further exploited as an additive for enhancing meat and milk quality in ruminants.

An Integrated Outlook on the Metagenome and Metabolome of Intestinal Diseases

Recently, metagenomics and metabolomics are the two most rapidly advancing “omics” technologies. Metagenomics seeks to characterize the composition of microbial communities, their operations, and their dynamically co-evolving relationships with the habitats they occupy, whereas metabolomics studies unique chemical endpoints (metabolites) that specific cellular processes leave behind. Remarkable progress in DNA sequencing and mass spectrometry technologies has enabled the comprehensive collection of information on the gut microbiome and its metabolome in order to assess the influence of the gut microbiota on host physiology on a whole-systems level. Our gut microbiota, which consists of prokaryotic cells together with its metabolites, creates a unique gut ecosystem together with the host eukaryotic cells. In this review, we will highlight the detailed relationships between gut microbiota and its metabolites on host health and the pathogenesis of various intestinal diseases such as inflammatory bowel disease and colorectal cancer. Therapeutic interventions such as probiotic and prebiotic administrations and fecal microbiota transplantations will also be discussed. We would like to promote this unique biology-wide approach of incorporating metagenome and metabolome information as we believe that this can help us understand the intricate interplay between gut microbiota and host metabolism to a greater extent. This novel integration of microbiome, metatranscriptome, and metabolome information will help us have an improved holistic understanding of the complex mammalian superorganism, thereby allowing us to gain new and unprecedented insights to providing exciting novel therapeutic approaches for optimal intestinal health.

Assessment of Fecal Microflora Changes in Pigs Supplemented with Herbal Residue and Prebiotic

Antibiotic usage in animals as a growth promoter is considered as public health issue due to its negative impact on consumer health and environment. The present study aimed to evaluate effectiveness of herbal residue (ginger, Zingiber officinale, dried rhizome powder) and prebiotic (inulin) as an alternative to antibiotics by comparing fecal microflora composition using terminal restriction fragment length polymorphism. The grower pigs were offered feed containing antibiotic (tetracycline), ginger and inulin separately and un-supplemented group served as control. The study revealed significant changes in the microbial abundance based on operational taxonomic units (OTUs) among the groups. Presumptive identification of organisms was established based on the fragment length of OTUs generated with three restriction enzymes (MspI, Sau3AI and BsuRI). The abundance of OTUs representing Bacteroides intestinalis, Eubacterium oxidoreducens, Selonomonas sp., Methylobacterium sp. and Denitrobacter sp. was found significantly greater in inulin supplemented pigs. Similarly, the abundance of OTUs representing Bacteroides intestinalis, Selonomonas sp., and Phascolarcobacterium faecium was found significantly greater in ginger supplemented pigs. In contrast, the abundance of OTUs representing pathogenic microorganisms Atopostipes suicloacalis and Bartonella quintana str. Toulouse was significantly reduced in ginger and inulin supplemented pigs. The OTUs were found to be clustered under two major phylotypes; ginger-inulin and control-tetracycline. Additionally, the abundance of OTUs was similar in ginger and inulin supplemented pigs. The results suggest the potential of ginger and prebioticsto replace antibiotics in the diet of grower pig.

Toward the comprehensive understanding of the gut ecosystem via metabolomics-based integrated omics approach

Recent advances in DNA sequencing and mass spectrometry technologies have allowed us to collect more data on microbiome and metabolome to assess the influence of the gut microbiota on human health at a whole-systems level. Major advances in metagenomics and metabolomics technologies have shown that the gut microbiota contributes to host overall health status to a large extent. As such, the gut microbiota is often likened to a measurable and functional organ consisting of prokaryotic cells, which creates the unique gut ecosystem together with the host eukaryotic cells. In this review, we discuss in detail the relationship between gut microbiota and its metabolites like choline, bile acids, phenols, and short-chain fatty acids in the host health and etiopathogenesis of various pathological states such as multiple sclerosis, autism, obesity, diabetes, and chronic kidney disease. By integrating metagenomic and metabolomic information on a systems biology-wide approach, we would be better able to understand this interplay between gut microbiome and host metabolism. Integration of the microbiome, metatranscriptome, and metabolome information will pave the way toward an improved holistic understanding of the complex mammalian superorganism. Through the modeling of metabolic interactions between lifestyle, diet, and microbiota, integrated omics-based understanding of the gut ecosystem is the new avenue, providing exciting novel therapeutic approaches for optimal host health.

Gut microbiome and metabolic diseases

The prevalence of obesity and obesity-related disorders is increasing worldwide. In the last decade, the gut microbiota has emerged as an important factor in the development of obesity and metabolic syndrome, through its interactions with dietary, environmental, and host genetic factors. Various studies have shown that alteration of the gut microbiota, shifting it toward increased energy harvest, is associated with an obese phenotype. However, the molecular mechanisms by which the gut microbiota affects host metabolism are still obscure. In this review, we discuss the complexity of the gut microbiota and its relationship to obesity and obesity-related diseases. Furthermore, we discuss the anti-obesity potential of probiotics and prebiotics.

Use of 'natural' products as alternatives to antibiotic feed additives in ruminant production

The banning in 2006 of the use of antibiotics as animal growth promoters in the European Union has increased demand from producers for alternative feed additives that can be used to improve animal production. This review gives an overview of the most common non-antibiotic feed additives already being used or that could potentially be used in ruminant nutrition. Probiotics, dicarboxylic acids, enzymes and plant-derived products including saponins, tannins and essential oils are presented. The known modes of action and effects of these additives on feed digestion and more especially on rumen fermentations are described. Their utility and limitations in field conditions for modern ruminant production systems and their compliance with the current legislation are also discussed.

Method for screening of bacterial strains biosynthesizing specific conjugated linoleic acid isomers

A simple and accurate method for screening of bacterial strains with the ability to convert free linoleic acid into specific conjugated linoleic acid (CLA) isomers has been developed by combining the ultraviolet spectral scan and capillary electrophoresis analysis. The ultraviolet spectral scan was carried out for preliminary screening of bacterial strains with the capacity to biosynthesize CLA, and the absorption peak at 228-235 nm was used for assessing the possible production of CLA by bacteria. The capillary electrophoresis analysis was used as the follow-up confirmation to definitively conclude CLA production and the composition of CLA isomers. Linoleic acid at the concentration of 25 μg/mL, which showed little inhibitory effect on the growth of bacteria, was used for initial screening of CLA-producing strains. The strains with the ability to produce specific CLA isomers can be selected quickly from a large number of bacteria by this high-throughput method.

Catalytic production of conjugated fatty acids and oils

The reactive double bonds in conjugated vegetable oils are of high interest in industry. Traditionally, conjugated vegetable oils are added to paints, varnishes, and inks to improve their drying properties, while recently there is an increased interest in their use in the production of bioplastics. Besides the industrial applications, also food manufactures are interested in conjugated vegetable oils due to their various positive health effects. While the isomer type is less important for their industrial purposes, the beneficial health effects are mainly associated with the c9,t11, t10,c12 and t9,t11 CLA isomers. The production of CLA-enriched oils as additives in functional foods thus requires a high CLA isomer selectivity. Currently, CLAs are produced by conjugation of oils high in linoleic acid, for example soybean and safflower oil, using homogeneous bases. Although high CLA productivities and very high isomer selectivities are obtained, this process faces many ecological drawbacks. Moreover, CLA-enriched oils can not be produced directly with the homogeneous bases. Literature reports describe many catalytic processes to conjugate linoleic acid, linoleic acid methyl ester, and vegetable oils rich in linoleic acid: biocatalysts, for example enzymes and cells; metal catalysts, for example homogeneous metal complexes and heterogeneous catalysts; and photocatalysts. This Review discusses state-of-the-art catalytic processes in comparison with some new catalytic production routes. For each category of catalytic process, the CLA productivities and the CLA isomer selectivity are compared. Heterogeneous catalysis seems the most attractive approach for CLA production due to its easy recovery process, provided that the competing hydrogenation reaction is limited and the CLA production rate competes with the current homogeneous base catalysis. The most important criteria to obtain high CLA productivity and isomer selectivity are (1) absence of a hydrogen donor, (2) absence of catalyst acidity, (3) high metal dispersion, and (4) highly accessible pore architecture.

Trans-18:1 and conjugated linoleic acid profiles after the inclusion of buffer, sodium sesquicarbonate, in the concentrate of finishing steers

Ninety-six European crossbred steers were fed a barley-based finishing diet for differing lengths of time (34-104 days) to investigate if adding dietary buffer (sodium sesquicarbonate at 1.5% as fed) could improve the trans-18:1 (GC-FID) and CLA (Ag(+)-HPLC-DAD) content and isomeric profile of beef produced. Results indicate that the addition of buffer to diets of cattle fed high concentrate diets has limited effects on the overall fatty acid composition of backfat and muscle tissues. However, buffer addition can help to prevent a 10t- shift by maintaining a better (higher) 11t-/10t-18:1 ratio in both meat and backfat during the first 30-60 days of feeding a high grain diet. Over time, however, the effect is lost becoming equal in tissues from animals with or without buffer addition to their diets.

Evaluation and characterization of bacterial metabolic dynamics with a novel profiling technique, real-time metabolotyping

BACKGROUND

Environmental processes in ecosystems are dynamically altered by several metabolic responses in microorganisms, including intracellular sensing and pumping, battle for survival, and supply of or competition for nutrients. Notably, intestinal bacteria maintain homeostatic balance in mammals via multiple dynamic biochemical reactions to produce several metabolites from undigested food, and those metabolites exert various effects on mammalian cells in a time-dependent manner. We have established a method for the analysis of bacterial metabolic dynamics in real time and used it in combination with statistical NMR procedures.

METHODOLOGY/PRINCIPAL FINDINGS

We developed a novel method called real-time metabolotyping (RT-MT), which performs sequential (1)H-NMR profiling and two-dimensional (2D) (1)H, (13)C-HSQC (heteronuclear single quantum coherence) profiling during bacterial growth in an NMR tube. The profiles were evaluated with such statistical methods as Z-score analysis, principal components analysis, and time series of statistical TOtal Correlation SpectroScopY (TOCSY). In addition, using 2D (1)H, (13)C-HSQC with the stable isotope labeling technique, we observed the metabolic kinetics of specific biochemical reactions based on time-dependent 2D kinetic profiles. Using these methods, we clarified the pathway for linolenic acid hydrogenation by a gastrointestinal bacterium, Butyrivibrio fibrisolvens. We identified trans11, cis13 conjugated linoleic acid as the intermediate of linolenic acid hydrogenation by B. fibrisolvens, based on the results of (13)C-labeling RT-MT experiments. In addition, we showed that the biohydrogenation of polyunsaturated fatty acids serves as a defense mechanism against their toxic effects.

CONCLUSIONS

RT-MT is useful for the characterization of beneficial bacterium that shows potential for use as probiotic by producing bioactive compounds.

Culture-independent identification of gut bacteria correlated with the onset of diabetes in a rat model

Bacteria associated with the onset of type 1 diabetes in a rat model system were identified. In two experiments, stool samples were collected at three time points after birth from bio-breeding diabetes-prone (BB-DP) and bio-breeding diabetes-resistant (BB-DR) rats. DNA was isolated from these samples and the 16S rRNA gene was amplified using universal primer sets. In the first experiment, bands specific to BB-DP and BB-DR genotypes were identified by automated ribosomal intergenic spacer analysis at the time of diabetes onset in BB-DP. Lactobacillus and Bacteroides strains were identified in the BB-DR- and BB-DP-specific bands, respectively. Sanger sequencing showed that the BB-DP and BB-DR bacterial communities differed significantly but too few reads were available to identify significant differences at the genus or species levels. A second experiment confirmed these results using higher throughput pyrosequencing and quantitative PCR of 16S rRNA with more rats per genotype. An average of 4541 and 3381 16S rRNA bacterial reads were obtained from each of the 10 BB-DR and 10 BB-DP samples collected at time of diabetes onset. Nine genera were more abundant in BB-DP whereas another nine genera were more abundant in BB-DR. Thirteen and eleven species were more abundant in BB-DP and BB-DR, respectively. An average of 23% and 10% of all reads could be classified at the genus and species levels, respectively. Quantitative PCR verified the higher abundance of Lactobacillus and Bifidobacterium in the BB-DR samples. Whether these changes are caused by diabetes or are involved in the development of the disease is unknown.

Ruminal biohydrogenation as affected by tanninsin vitro

The aim of the present work was to study the effects of tannins from carob (CT;Ceratonia siliqua), acacia leaves (AT;Acacia cyanophylla) and quebracho (QT;Schinopsis lorentzii) on ruminal biohydrogenationin vitro.The tannins extracted from CT, AT and QT were incubated for 12 h in glass syringes in cow buffered ruminal fluid (BRF) with hay or hay plus concentrate as a substrate. Within each feed, three concentrations of tannins were used (0·0, 0·6 and 1·0 mg/ml BRF). The branched-chain volatile fatty acids, the branched-chain fatty acids and the microbial protein concentration were reduced (P < 0·05) by tannins. In the tannin-containing fermenters, vaccenic acid was accumulated (+23 %,P < 0·01) while stearic acid was reduced ( − 16 %,P < 0·0005). The concentration of total conjugated linoleic acid (CLA) isomers in the BRF was not affected by tannins. The assay on linoleic acid isomerase (LA-I) showed that the enzyme activity (nmol CLA produced/min per mg protein) was unaffected by the inclusion of tannins in the fermenters. However, the CLA produced by LA-I (nmol/ml per min) was lower in the presence of tannins. These results suggest that tannins reduce ruminal biohydrogenation through the inhibition of the activity of ruminal micro-organisms.

Accumulation of trans C18:1 fatty acids in the rumen after dietary algal supplementation is associated with changes in the Butyrivibrio community

Optimization of the fatty acid composition of ruminant milk and meat is desirable. Dietary supplementation of algae was previously shown to inhibit rumen biohydrogenation, resulting in an altered milk fatty acid profile. Bacteria involved in biohydrogenation belong to the Butyrivibrio group. This study was aimed at relating accumulation of biohydrogenation intermediates with shifts in Butyrivibrio spp. in the rumen of dairy cows. Therefore, an experiment was performed with three rumen-fistulated dairy cows receiving a concentrate containing algae (9.35 g/kg total dry matter [DM] intake) for 20 days. Supplementation of the diet with algae inhibited biohydrogenation of C(18:2) omega 6 (n-6) and C(18:3) n-3, resulting in increased concentrations of biohydrogenation intermediates, whereas C(18:0) decreased. Addition of algae increased ruminal C(18:1) trans fatty acid concentrations, mainly due to 6- and 20-fold increases in C(18:1) trans 11 (t11) and C(18:1) t10. The number of ciliates (5.37 log copies/g rumen digesta) and the composition of the ciliate community were unaffected by dietary algae. In contrast, supplementation of the diet with algae changed the composition of the bacterial community. Primers for the Butyrivibrio group, including the genera Butyrivibrio and Pseudobutyrivibrio, were specifically designed. Denaturing gradient gel electrophoresis showed community changes upon addition of algae without affecting the total amount of Butyrivibrio bacteria (7.06 log copies/g rumen DM). Clone libraries showed that algae affected noncultivated species, which cluster taxonomically between the genera Butyrivibrio and Pseudobutyrivibrio and might play a role in biohydrogenation. In addition, 20% of the clones from a randomly selected rumen sample were related to the C(18:0)-producing branch, although the associated C(18:0) concentration decreased through supplementation of the diet with algae.

Studies on the production of conjugated linoleic acid from linoleic and vaccenic acids by mixed rumen protozoa

The present study was designed to investigate the capability of mixed rumen protozoa to synthesize conjugated linoleic acid (CLA) from linoleic (LA) and vaccenic acids (VA). Rumen contents were collected from fistulated cows. The protozoal fraction was separated and washed several times with MB9 buffer and then resuspended in autoclaved rumen fluid. The suspensions were anaerobically incubated up to 18 h at 38.5 degrees C with substrates in the presence (P-AB) or the absence of antibacterial-agents (P-No-AB). Neither P-AB nor P-No-AB suspensions were capable of producing CLA from VA (11t-18:1). Linoleic acid was catabolized by P-No-AB to a greater extent than P-AB. Different isomers of CLA were synthesized by P-AB from LA. The 9c11t-CLA was predominant. Thirty seven percent of the maximum accumulated 9c11t-CLA was found in the P-AB suspension as early as 0.1 h into the incubation period. Accumulation of 10t12c-CLA in P-AB suspension was approximately 10.0 times lower than that of 9c11t-CLA. There were no significant productions of VA, 10t-18:1, and 18:0 in P-AB compared with the control, indicating that rumen protozoa have no ability to biohydrogenate CLA isomers. On the other hand, the concentrations of 10t-18:1, VA, and 18:0 in P-No-AB were greater (P < 0.05) compared with those in P-AB, indicating the role of symbiotic bacteria associated with P-No-AB in biohydrogenating CLA isomers. We concluded that mixed rumen protozoa are capable of synthesizing CLA from LA through isomerization reactions. However, they are incapable of metabolizing CLA further. They are also incapable of vaccenic acid biohydrogenation and/or desaturation.

Purification and gene sequencing of conjugated linoleic acid reductase from a gastrointestinal bacterium, Butyrivibrio fibrisolvens

AIMS

To characterize the cause for the lack of conjugated linoleic acid (CLA) reductase (CLA-R) activity in the Butyrivibrio fibrisolvens MDT-5 strain that rapidly isomerizes linoleic acid (LA) to CLA without hydrogenation, the CLA-R was purified and its gene (cla-r) sequence was determined.

METHODS AND RESULTS

CLA-R was purified to near homogeneity as a 53-kDa monomeric protein from the high CLA-R activity-expressing strain MDT-10. The purified CLA-R recognized conjugated double bonds. Unsaturated fatty acids containing 18 carbons markedly increased the CLA-R expression at the transcriptional level. Complete sequencing of the cla-r gene revealed that the CLA-R is a novel protein. Sequence analysis of the cla-r gene from the MDT-5 strain revealed that the MDT-5 CLA-R protein sequence differed from that of the MDT-10 at four consecutive amino acids. Northern and Western blotting analyses confirmed that the cla-r mRNA and protein are expressed normally in MDT-5.

CONCLUSIONS

Strain MDT-5 expresses the CLA-R protein that lacks enzyme activity because of mutation, which explains why MDT-5 exclusively produces CLA from LA.

SIGNIFICANCE AND IMPACT OF THE STUDY

The cla-r gene was sequenced for the first time. Exogenous fatty acids affected the cla-r transcription. These results will provide additional knowledge on biohydrogenation, and may also augment the CLA production in the gastrointestinal tract.

Vaccenic acid and cis-9,trans-11 CLA in the rumen and different tissues of pasture- and concentrate-fed beef cattle

The objective of present study was the comparison of trans-11 18:1 (VA) and cis-9,trans-11 CLA concentrations in the rumen and different tissues in beef cattle, and to examine the diet and breed effects on the compound concentration and deposition. Sixty-four German Holstein and German Simmental bulls were randomly assigned to two dietary treatments, based on concentrate or pasture. The concentration of cis-9,trans-11 CLA and VA in rumen, duodenal digesta and different tissues was determined by gas chromatography. The results showed that pasture relative to concentrate feeding significantly increased the concentration of VA in duodenal digesta, plasma and erythrocyte phospholipids. Pasture-based feeding resulted in a significant enrichment of cis-9,trans-11 CLA in plasma lipids and erythrocyte phospholipids, but not in rumen and duodenal digesta, compared to concentrate-fed diet. Diet did not affect the cis-9,trans-11 CLA concentrations (mg/100 g fresh tissue) in semitendinosus muscle and subcutaneous fat. There was a breed effect on the deposition of cis-9,trans-11 CLA in longissimus muscle with lower concentration in pasture-fed German Simmental bulls compared to concentrate-fed bulls. However, pasture feeding significantly increased both, the VA and cis-9,trans-11 CLA concentrations in liver and heart tissues. Both diet and breed effects on Delta(9)-desaturase index was observed in muscle and subcutaneous fat tissues. There was a linear relationship between the concentration of VA and cis-9,trans-11 CLA and the coefficients of determination (R (2)) varied between 0.29 and 0.87 from rumen to the different tissues.