Production of bioactive conjugated linoleic acid by the multifunctional enolase from Lactobacillus plantarum

Production of Conjugated Linoleic Acid (CLA) by Lactiplantibacillus plantarum: A Review with Emphasis on Fermented Foods

The term Conjugated Linoleic Acid (CLA) refers generically to a class of positional and geometric conjugated dienoic isomers of linoleic acid. Among the isomers of linoleic acid cis9, trans11-CLA (c9, t11-CLA) and trans10, cis12-CLA (t10, c12-CLA) are found to be biologically active isomers, and they occur naturally in milk, dairy products and meat from ruminants. In addition, some vegetables and some seafoods have also been reported to contain CLA. Although the CLA levels in these natural sources are insufficient to confer the essential health benefits, anti-carcinogenic or anti-cancer effects are of current interest. In the rumen, CLA is an intermediate of isomerization and the biohydrogenation process of linoleic acid to stearic acid conducted by ruminal microorganisms. In addition to rumen bacteria, some other bacteria, such as Propionibacterium, Bifidobacterium and some lactic acid bacteria (LAB) are also capable of producing CLA. In this regard, Lactiplantibacillus plantarum (formerly Lactobacillus plantarum) has demonstrated the ability to produce CLA isomers from linoleic acid by multiple enzymatic activities, including hydration, dehydration, and isomerization. L. plantarum is one of the most versatile species of LAB and the bacterium is widely used in the food industry as a microbial food culture. Thus, in this review we critically analyzed the literature produced in the last ten years with the aim to highlight the potentiality as well as the optimal conditions for CLA production by L. plantarum. Evidence was provided suggesting that the use of appropriate strains of L. plantarum, as a starter or additional culture in the production of some fermented foods, can be considered a critical factor in the design of new CLA-enriched functional foods.

Probiotic Properties of Lactic Acid Bacteria with High Conjugated Linoleic Acid Converting Activity Isolated from Jeot-Gal, High-Salt Fermented Seafood

Conjugated linoleic acid (CLA) isomers are potent health-promoting fatty acids. This study evaluated the probiotic properties of 10 strains of high CLA-producing lactic acid bacteria (LAB) isolated from Jeot-gal, a high-salt, fermented seafood. Two isolates, Lactiplantibacillus plantarum JBCC105683 and Lactiplantibacillus pentosus JBCC105676, produced the largest amounts of CLA (748.8 and 726.9 μg/mL, respectively). Five isolates, L. plantarum JBCC105675, L. pentosus JBCC105676, L. pentosus JBCC105674, L. plantarum JBCC105683, and Lactiplantibacillus paraplantarum JBCC105655 synthesized more cis-9, trans-11-CLA than trans-10, cis-12-CLA (approximately 80:20 ratio). All the strains survived severe artificial acidic environments and showed antimicrobial activity and strong adhesion capability to Caco-2 cells as compared to the commercial strain Lactocaseibacillus rhamnosus GG. Among them, Pediococcus acidilactici JBCC105117, L. paraplantarum JBCC105655, and L. plantarum JBCC105683 strongly stimulated the immunological regulatory gene PMK-1 and the host defense antimicrobial peptide gene clec-60 in Caenorhabditis elegans. Moreover, three strains showed a significant induction of tumor necrosis factor-α, interleukin (IL)-1β, IL-6, IL-12, and IL-10 production in RAW 264.7 macrophages, indicating that they were promising candidates for probiotics with high CLA-converting activity. Our results indicate that the newly isolated CLA-producing LAB might be useful as a functional probiotic with beneficial health effects that modulate the immune system.

Antimicrobial Biomasses from Lactic Acid Fermentation of Black Soldier Fly Prepupae and Related By-Products

Worldwide, thousands of insect species are consumed as food or are used as feed ingredients. Hermetia illucens, ‘black soldier fly’, is one of them, and a large amount of puparia and dead adults flies are accumulated during rearing. These materials represent important wastes but no studies are still present in the literature regarding their functional properties and potential reuse. Lactic acid bacteria (LAB) are a heterogeneous group of bacteria contributing to various industrial applications, ranging from food fermentation, chemicals production to pharmaceuticals manufacturing. A LAB feature of industrial interest is their ability to produce antimicrobial metabolites. Considering the scientific and commercial interest in discovering novel antimicrobials, this work will be direct towards fermentation of insect-derived biomasses: puparia and adults insect at the end of life cycle. To the best of our knowledge, the in vitro antimicrobial activity of fermented insects is tested for the first time. This study aimed also to evaluate differences in the composition between fermented and unfermented insects, and to study whether the fermentation and the type of LAB used played a crucial role in modifying the composition of the substrate. Results firstly highlighted fermentability of this species of insects, showed that fermented black soldier flies puparium possess a high antimicrobial activity against tested pathogens. Moreover, result of chemical composition showed that fermented biomass had a higher percentage of fat and a more complex fatty acids profile.

Kinetics and function of two mutants of CLA hydrase from Lactobacillus plantarum p-8

In this work, the gene of conjugated linoleic acid hydrase (CLA-HY) was cloned from L. plantarum p-8, and the protein of CLA-HY was expressed in Escherichia coli BL21. Gas chromatography-mass spectrometry was employed to verify that the purified CLA-HY can convert linoleic acid (LA) into 10-hydroxy-cis-12-octadecenoic acid (10-HOE) in the presence of flavin adenine dinucleotide (FAD). The optimal pH and temperature for maximizing CLA-HY catalytic activity were found to be 6.0 and 35°C, respectively. In addition, the catalytic ability of CLA-HY can be inhibited by a number of cations such as Mg2+, Mn2+, Zn2+, Cu2+, Fe2+, Fe3+, Ni2+ and Ca2+. Finally, the Km,Vmax, Kcat and Kcat/Km of CLA-HY were determined as 7.62 mM, 2.59 mM h-1, 8.33 × 103 h-1 and 1.09 × 103 mM-1 h-1, respectively. Moreover, it was demonstrated that both M76 and G74 residues played significant roles in catalysing the conversion of LA into 10-HOE using site-directed mutation technology and molecular simulations.

Anti-atherosclerotic effects of Lactobacillus plantarum ATCC 14917 in ApoE-/- mice through modulation of proinflammatory cytokines and oxidative stress

Atherosclerosis is a chronic inflammatory disease mediated by monocyte infiltration and cholesterol deposition into the subendothelial area, resulting in foam cell development. Probiotics are live bacteria that are beneficial for health when administered orally in adequate amounts. In this study, 8-week-old atherosclerosis-prone apolipoprotein E-deficient (ApoE^-/-) mice were fed with or without Lactobacillus plantarum ATCC 14917 per day for 12 weeks. Serum was collected to analyse the lipid profile, oxidative status and proinflammatory cytokines. The heart was isolated to quantify the atherosclerotic lesion size in the aortic arch. Quantitative real-time polymerase chain reaction was performed to determine the expression levels of tumour necrosis factor-alpha (TNF-α) and interleukin (IL)-1β in the aorta. The proteins extracted from the aorta were used for Western blot analysis to assess the expression levels of nuclear factor kappa B (NF-κB) and inhibitor of NF-κB (IκBα). The composition of gut microbiota was also examined through high-throughput sequencing. Results showed that the daily consumption of L. plantarum ATCC 14917 had no effect on body weight and lipid profile. L. plantarum ATCC 14917 treatment significantly inhibited atherosclerotic lesion formation. In addition, the oxLDL, MDA, TNF-α and IL-1β levels were significantly reduced, whereas the SOD level was induced in the bacteria + high-fat diet group. Furthermore, the administration of L. plantarum ATCC 14917 significantly attenuated IκBα protein degradation and inhibited the translocation of P65 subunits of NF-κB. L. plantarum ATCC 14917 treatment also modulated the composition of gut microbiota in ApoE^-/- mice. Our findings showed that L. plantarum ATCC 14917 supplementation decreases the progression of atherosclerotic lesion formation by alleviating the inflammatory process and lowering oxidative stress.

Effects of Linoleic Acid on Gut-Derived Bifidobacterium breve DSM 20213: A Transcriptomic Approach

Bacterial production of conjugated linoleic acid (CLA) has recently received great attention because of the potential health benefits of this fatty acid. Linoleic acid (LA) can be converted to CLA by several microorganisms, including bifidobacteria, possibly as a detoxification mechanism to avoid the growth inhibition effect of LA. In the present in vitro study, we investigated the gene expression landscape of the intestinal strain Bifidobacterium breve DSM 20213 when exposed to LA. Transcriptomic analysis using RNA-seq revealed that LA induced a multifactorial stress response in the test strain, including upregulation of genes involved in iron uptake and downregulation of genes involved in sugar and oligopeptide transport. We also observed reduced transcription of genes involved in membrane and pili biosynthesis. The upregulation of iron uptake was not related to any putative ability of LA to chelate Fe²⁺, but was somewhat linked to stress response. Furthermore, we demonstrated that LA increased reactive oxygen species (ROS) production in bacterial cells, activating an oxidative stress response. This response was proved by thioredoxin reductase transcription, and was primarily evident among bacteria cultured in the absence of cysteine. This is the first report of the potential mechanisms involved in bacterial LA transport and stress response in B. breve.

The Eno Gene of Burkholderia cenocepacia Strain 71-2 is Involved in Phosphate Solubilization

Bacterial strain 71-2 with phosphate-solubilizing activity was isolated from tobacco rhizosphere and classified as Burkholderia cenocepacia based on sequence analyses of 16S rRNA and recA genes. To learn phosphate-solubilizing mechanisms of 71-2, mutants showing reduced solubilizing phosphate activity were obtained using the EZ-Tn5 transposon. Mutant 71-2-MT51 was reduced in the solubilizing phosphate content to 34.36% as compared with the wild-type strain 71-2. The disrupted gene in 71-2-MT51 was cloned and sequenced, and the putative protein from the gene shared 65.26% identity to protein sequences of enolase from Escherichia coli, which suggests the gene encodes an enzyme of enolase. Complementation analyzing showed that Eno was responsible for phosphate solubilizing for B. cenocepacia strain 71-2. To our knowledge, this is the first report of Eno involved in phosphate solubilizing in B. cenocepacia as well as in other bacteria.

An integrated metabolomics and 16S rRNA gene sequencing approach exploring the molecular pathways and potential targets behind the effects of Radix Scrophulariae

To assess the impact of the caecal microbiota on faecal metabolic phenotypes in the presence of Radix Scrophulariae (Chinese name: Xuanshen), an integrated approach involving 16S rRNA gene sequencing combined with ultrahigh-performance liquid chromatography/time-of-flight mass spectrometry (UHPLC/TOF-MS)-based faecal metabolomics was applied to Radix Scrophulariae-treated rats. Interestingly, Radix Scrophulariae led to significant gut microbiota changes at the phylum and genus levels in treated rats compared to control rats. Additionally, distinct changes in faecal metabolites, including linoleic acid (LA), guanosine, inosine, hypoxanthine, xanthine, 4-hydroxycinnamic acid, cholic acid, N-acetyl-d-glucosamine, l-urobilinogen and uridine, were observed in Radix Scrophulariae-treated rats. Of these, seven metabolites were up-regulated, and the remaining three metabolites were down-regulated. Moreover, there were substantial associations between altered levels of gut microbiota genera and discrepant levels of faecal metabolites, particularly for compounds involved in LA and purine metabolism. These results demonstrated that the gut microbiota is altered in association with faecal metabolism following treatment with Radix Scrophulariae. Our findings suggest that further application of this 16S rRNA gene sequencing and UHPLC/TOF-MS-based metabolomics approach will facilitate the assessment of the pharmacological action of Radix Scrophulariae and thus expand the scope of this herb.

An integrated approach to assess impact of caecal microbiota on faecal metabolic phenotypes in the presence of Radix Scrophulariae involving 16S rRNA gene sequencing combined with UHPLC/TOF-MS-based faecal metabolomics was applied to Radix Scrophulariae-treated rats.

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.

The first complete genomic structure of Butyrivibrio fibrisolvens and its chromid

Butyrivibrio fibrisolvens forms part of the gastrointestinal microbiome of ruminants and other mammals, including humans. Indeed, it is one of the most common bacteria found in the rumen and plays an important role in ruminal fermentation of polysaccharides, yet, to date, there is no closed reference genome published for this species in any ruminant animal. We successfully assembled the nearly complete genome sequence of B. fibrisolvens strain INBov1 isolated from cow rumen using Illumina paired-end reads, 454 Roche single-end and mate pair sequencing technology. Additionally, we constructed an optical restriction map of this strain to aid in scaffold ordering and positioning, and completed the first genomic structure of this species. Moreover, we identified and assembled the first chromid of this species (pINBov266). The INBov1 genome encodes a large set of genes involved in the cellulolytic process but lacks key genes. This seems to indicate that B. fibrisolvens plays an important role in ruminal cellulolytic processes, but does not have autonomous cellulolytic capacity. When searching for genes involved in the biohydrogenation of unsaturated fatty acids, no linoleate isomerase gene was found in this strain. INBov1 does encode oleate hydratase genes known to participate in the hydrogenation of oleic acids. Furthermore, INBov1 contains an enolase gene, which has been recently determined to participate in the synthesis of conjugated linoleic acids. This work confirms the presence of a novel chromid in B. fibrisolvens and provides a new potential reference genome sequence for this species, providing new insight into its role in biohydrogenation and carbohydrate degradation.

Proteome and phospholipid alteration reveal metabolic network of Bacillus thuringiensis under triclosan stress

Triclosan is a common antibacterial agent widely applied in various household and personal care products. The molecule, cell, organ and organism-level understanding of its toxicity pose to some target organisms has been investigated, whereas, the alteration of a single metabolic reaction, gene or protein cannot reflect the impact of triclosan on metabolic network. To clarify the interaction between triclosan stress and metabolism at network and system levels, phospholipid synthesis, and cellular proteome and metabolism of Bacillus thuringiensis under 1μM of triclosan stress were investigated through omics approaches. The results showed that C14:0, C16:1ω7, C16:0 and C18:2ω6 were significantly up-produced, and 19 proteins were differentially expressed. Whereas, energy supply, protein repair and the synthesis of DNA, RNA and protein were down-regulated. PyrH and Eno could be biomarkers to reflect triclosan stress. At network level, the target proteins ACOX1, AHR, CAR, CYP1A, CYP1B1, DNMT1, ENO, HSP60, HSP70, SLC5A5, TPO and UGT expressed in different species shared high sequence homology with the same function proteins found in Homo sapiens not only validated their role as biomarkers but also implied the potential impact of triclosan on the metabolic pathways and network of humans. These findings provided novel insights into the metabolic influence of triclosan at network levels, and developed an omics approach to evaluate the safety of target compound.

Gene expression profile changes in the jejunum of weaned piglets after oral administration of Lactobacillus or an antibiotic

The small intestine plays an essential role in the health and well-being of animals. Previous studies have shown that Lactobacillus has a protective effect on intestinal morphology, intestinal epithelium integrity and appropriate maturation of gut-associated tissues. Here, gene expression in jejunum tissue of weaned piglets was investigated by RNA-seq analysis after administration of sterile saline, Lactobacillus reuteri, or an antibiotic (chlortetracycline). In total, 401 and 293 genes were significantly regulated by chlortetracycline and L. reuteri, respectively, compared with control treatment. Notably, the HP, NOX1 and GPX2 genes were significantly up-regulated in the L. reuteri group compared with control, which is related to the antioxidant ability of this strain. In addition, the expression of genes related to arachidonic acid metabolism and linoleic acid metabolism enriched after treatment with L. reuteri. The fatty acid composition in the jejunum and colon was examined by GC-MS analysis and suggested that the MUFA C18:1n9c, and PUFAs C18:2n6c and C20:4n6 were increased in the L. reuteri group, verifying the GO enrichment and KEGG pathway analyses of the RNA-seq results. The results contribute to our understanding of the probiotic activity of this strain and its application in pig production.

Characterization of the triple-component linoleic acid isomerase in Lactobacillus plantarum ZS2058 by genetic manipulation

AIM

To assess the mechanism for conjugated linoleic acid (CLA) production in Lactobacillus plantarum ZS2058.

METHODS AND RESULTS

CLA has attracted great interests for decades due to its health-associated benefits including anticancer, anti-atherogenic, anti-obesity and modulation of the immune system. A number of microbial CLA producers were widely reported including lactic acid bacteria. Lactobacillus plantarum ZS2058, an isolate from Chinese traditional fermented food, could convert LA to CLA with various intermediates. To characterize the genetic determinants for generating CLA, a cre-lox-based system was utilized to delete the genes encoding myosin cross-reactive antigen (MCRA), short-chain dehydrogenase/oxidoreductase (DH) and acetoacetate decarboxylase (DC) in Lact. plantarum ZS2058, respectively. Neither intermediate was detected in the corresponding gene deletion mutant. Meanwhile all those mutants could recover the ability to convert linoleic acid to CLA when the corresponding gene was completed.

CONCLUSIONS

The results indicated that CLA production was a multiple-step reaction catalysed by triple-component linoleate isomerase system encoded by mcra, dh and dc.

SIGNIFICANCE AND IMPACT OF THE STUDY

Multicomponent linoleic acid isomerase provided important results for illustration unique mechanism for CLA production in Lact. plantarum ZS2058. Lactobacilli with CLA production ability offer novel opportunities for functional food development.

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.