Co-precipitation Of Cholesterol Research Articles

Unleashing the Potential of Gut Microbiota: Cholesterol Reduction Through Microbial Bile Acid Metabolism

Abstract: Cholesterol metabolism is a crucial mechanism for preserving cellular functionality, and overall human health. Cardiovascular diseases and other conditions can arise due to dysregulation of cholesterol levels. Bile acids’ enterohepatic circulation greatly influences cholesterol homeostasis. Recent research has emphasized the essential role of the gut microbiota in bile acid metabolism and its association with cholesterol regulation. Living microbial supplements known as probiotics have been studied as a potential means of reducing cholesterol by modifying the gut microbiome. This review explores existing theories of how probiotic production and modification of bile acids affect cholesterol metabolism. Discussion ensues regarding the processes by which probiotics lower cholesterol, including bile acid deconjugation, conversion of cholesterol to coprostanol and cholestenone, co-precipitation of cholesterol with deconjugated bile, and disruption of cholesterol micelles by Bile Salt Hydrolase (BSH). According to research, there are significant therapeutic ramifications in understanding the complex interactions between the gut microbiome and host cholesterol metabolism. More research is required to comprehend the causal mechanisms further and produce new methods for lowering microbiota-mediated cholesterol to improve human health.

Bile salt deconjugation and in-vitro cholesterol-lowering ability of probiotic bacteria isolated from buttermilk

ABSTRACT Hypercholesterolemia prevalence is increasing in most countries and it increases the risk of microvascular and cardiovascular diseases. Currently available treatments include the use of statins, fibrates, and bile acid sequesters. These treatments carry a risk of severe side effects on the host. Probiotics are well documented for their cholesterol-lowering abilities. The present study has demonstrated the screening of probiotic bacteria from buttermilk samples, their ability to deconjugate bile salts, and cholesterol-lowering ability in the media. Bile salt hydrolysis by the isolates was evaluated by direct plate assay, thin layer chromatography, and cholic acid estimation. The highest amount of cholesterol was removed in the presence of 0.3% bile. Co-precipitation of cholesterol along with cholic acid was also observed. Three isolates considered potent based on their performance through all the tests were identified by 16S- rRNA gene sequencing as PGB01- Lacticaseibacillus paracasei, PGB02- Lactiplantibacillus plantarum, and PGB05- Lacticaseibacillus paracasei subsp. tolerans.

Transcriptional analysis for cholesterol-lowering effects of marine Lactobacillus plantarum Lp10 isolated from kelp

Lactobacillus plantarum, which exerts a variety of probiotic functions, has been recognized as a supplement for human foods with a widespread application. In this work, the cholesterol-lowering mechanisms of marine L. plantarum Lp10 were investigated by combining the analyses of transcriptome and quantitative real-time PCR. Results indicated that bile salt hydrolase (BSH) activity and extracellular polysaccharides (EPSs) adsorption were both responsible for cholesterol reduction. In this process, 11.1 million clean reads and 384 differentially expressed genes, including 79 up-regulated genes and 225 down-regulated genes, were obtained by transcriptome analysis. It was considered that EPS adsorption was mainly responsible for the cholesterol reduction without the influence of bile salt. Further analysis showed that the co-precipitation of cholesterol and deconjugated bile acids induced by BSH1 and BSH2 may play important role in the tolerance and reduction of cholesterol of strain under the stress condition with bile salt, in which, interestingly, the expressions of bsh3 and bsh4 were suppressed. In conclusion, the cholesterol-lowering mechanisms of marine L. plantarum Lp10 was investigated and it was considered as a potential strain for the application in cholesterol reduction.

Multifarious cholesterol lowering potential of lactic acid bacteria equipped with desired probiotic functional attributes.

Lactic acid bacteria (LAB) isolates possessed functional probiotic attributes, such as high hydrophobicity and autoaggregation ability, coaggregation capability with bacterial pathogens, antimicrobial activity, antioxidant potential, and hypocholesterolemic effects. Selected potential probiotic LAB, i.e. Lactobacillus paracasei M3, L. casei M5, L. paracasei M7, and few others were studied for their ability to lower cholesterol using a number of methods viz. cholesterol assimilation, bile salt deconjugation, cholesterol co-precipitation, cholesterol adhesion to probiotic cell wall, and miceller sequestration of cholesterol. L. casei M5 showed maximum bile salt hydrolase (BSH) activity, and released 57.63nmol of glycine/min, and was closely followed by LAB isolate M9 which generated 52.12nmol of glycine/min. Sodium glycocholate was deconjugated by L. casei M5 to produce 27.77μmol/mL of cholic acid, while other isolates produced 20-26μmol/mL of cholic acid. Cholesterol was assimilated significantly by isolate M6 (82.15%) and L. casei M5 (76.51%). L. casei M5 showed higher cholesterol co-precipitation ability (50.16μg/mL) as compared to other LAB isolates (33-44μg/mL). Miceller cholesterol concentration was reduced maximally byLAB isolate M8 (87.5%), followed by isolates M5 (84.75%), M9 (84%), M10 (80%), and M37 (79%). Higher cell wall adhesion of cholesterol was realized by L. casei M5 (42.48μg/mL) than other LAB isolates (30-40μg/mL). Selected LAB probiotics demonstrated short chain fatty acid (acetate, propionate, and butyrate) producing ability, yet another way of probiotics-mediated cholesterol lowering.

Interplay between Amphiphilic Stabilizers and Cholesterol in the Stabilization of Itraconazole Nanoparticles Prepared by Flash Nanoprecipitation.

While flash nanoprecipitation (FNP) has proven to be an extremely rapid and highly efficient nanoparticle fabrication process for hydrophobic drugs, physical instability associated with nonequilibrium molecular orientation of amphiphilic stabilizers (ASs) in nanoparticles remains a major snag in the general application of this nanotechnology, particularly for a drug with ACDLog P in the range of ∼2-9. This study was aimed at elucidating the costabilizing role of cholesterol (CLT) in the FNP of AS-stabilized nanoparticles of itraconazole (ITZ), a model drug with an ACDLog P of 4.35 ± 1.22 and log P of 5.66. The presence of CLT was shown to reduce the initial particle size and markedly improve the short-term storage stability of ITZ nanoparticles. The stability-enhancement by CLT can be linked to its higher miscibility or stronger interaction with the AS hydrophobic moiety than with ITZ (as reflected by the absolute differences of their solubility parameter values). Surface analyses employing X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) suggest that, through the coprecipitation of CLT with ITZ to form a mixed hydrophobic drug core, the CLT molecules that are exposed on the core surface serve to afford a stronger and more timely surface anchorage of the AS hydrophobic moieties, thereby facilitating the rearrangement of AS molecules toward the stable micelle-like structure. The present findings offer a mechanistic insight into the interplay between amphiphilic stabilizer and costabilizer in enhancing the physical stability of drug nanoparticles and may carry important implications for the development of more stable and efficacious nanoparticle therapeutics.

Screening of Indigenous Lactic Acid Bacteria for Cholesterol Lowering and Additional Probiotic Attributes

The study was aimed to evaluate the cholesterol lowering property and probiotic attributes of lactic acid bacteria (LAB) isolated from indigenous fermented milk products of Yak from the eastern region of Sikkim Himalayas. A total of 7 indigenous LAB were screened for putative probiotic features namely hypocholesterolaemic effect, bile salt hydrolase activity, acid tolerance and cell surface hydrophobocity. The possible mechanisms of cholesterol lowering like bile salt hydrolase (BSH) enzyme activity, bile acid deconjugation, cholesterol co-precipitation and cholesterol incorporation were studied. Isolates were subjected to direct plate assay in MRS agar plates supplemented with 0.5% (w/v) taurodeoxycholic acid sodium salt for the presence of bile salt hydrolase (BSH) enzyme. Screening revealed Lactobacillus paraplantarum YD11S and Lactobacillus plantarum YD5S showing bile acid deconjugation while co-precipitation was observed in YY1 Enterococcus lactis and Lactobacillus pentosus YD8S as the cholesterol lowering mechanism. Lactobacillus plantarum YD9S showed good bile acid deconjugation and co-precipation. Enterococcus faecium YHC12 was BSH-ve and showed cellular incorporation to be its mechanism of cholesterol lowering.

The perspective on cholesterol-lowering mechanisms of probiotics.

The use of probiotics as food components combats not only cardiovascular diseases but also many gastrointestinal tract disorders. Their health benefits along with their increased global market have interested scientists for better formulation and appropriate administration to the consumers. However, the lack of clear elucidation of their cholesterol-lowering mechanisms has complicated their proper dosage and administration to the beneficiaries. In this review, proposed mechanisms of cholesterol reduction such as deconjugation of bile via bile salt hydrolase activity, binding of cholesterol to probiotic cellular surface and incorporation into their cell membrane, production of SCFAs from oligosaccharides, coprecipitation of cholesterol with deconjugated bile, and cholesterol conversion to coprostanol have been discussed. Also, hypocholesterolemic effects on human- and animal-trial results, commonly used probiotics and synbiotics with effect on serum cholesterol regulation, types of bile salt hydrolase genes, and substrate specificities have been discussed.

Immobilization of bile salt hydrolase enzyme on mesoporous SBA-15 for co-precipitation of cholesterol

We describe herein a simple and effective strategy for immobilization of bile salt hydrolase enzyme by grafting glutaraldehyde groups inside channels of APTES functionalized SBA-15. The increase in glutaraldehyde concentration prevents leakage of enzyme but showed a steep decrease in enzyme activity in the immobilized matrix. So the degree of cross-linking should be the minimum possible to ensure sufficient stability without loss of activity. Cross-linking carried out with 0.1% glutaraldehyde concentration showed the highest activity, so this was used in all further experiments. Physico-chemical characterizations of the immobilized enzyme were carried out by XRD, N2 adsorption, TEM, FTIR and 29Si CP-MAS NMR techniques. Immobilized BSH exhibits enhanced stability over a wide pH (3–11) and temperature range (40–80°C) and retains an activity even after recycling experiments and six months of storage. From our in vivo research experiment toward co-precipitation of cholesterol, we have shown that immobilized BSH enzyme may be the promising catalyst for the reduction of serum cholesterol levels in our preliminary investigation. Enhancement in pH stability at the extreme side of pH may favor the use of immobilized BSH enzyme for drug delivery purpose to with stand extreme pH conditions in the gastrointestinal conditions.

Probiotic properties of Lactobacillus strains isolated from Tibetan kefir grains.

The objective of this study was to evaluate the functional properties of lactic acid bacteria (LAB) isolated from Tibetan kefir grains. Three Lactobacillus isolates identified as Lactobacillus acidophilus LA15, Lactobacillus plantarum B23 and Lactobacillus kefiri D17 that showed resistance to acid and bile salts were selected for further evaluation of their probiotic properties. The 3 selected strains expressed high in vitro adherence to Caco-2 cells. They were sensitive to gentamicin, erythromycin and chloramphenicol and resistant to vancomycin with MIC values of 26 µg/ml. All 3 strains showed potential bile salt hydrolase (BSH) activity, cholesterol assimilation and cholesterol co-precipitation ability. Additionally, the potential effect of these strains on plasma cholesterol levels was evaluated in Sprague-Dawley (SD) rats. Rats in 4 treatment groups were fed the following experimental diets for 4 weeks: a high-cholesterol diet, a high-cholesterol diet plus LA15, a high-cholesterol diet plus B23 or a high-cholesterol diet plus D17. The total cholesterol, triglyceride and low-density lipoprotein cholesterol levels in the serum were significantly (P<0.05) decreased in the LAB-treated rats compared with rats fed a high-cholesterol diet without LAB supplementation. The high-density lipoprotein cholesterol levels in groups B23 and D17 were significantly (P<0.05) higher than those in the control and LA15 groups. Additionally, both fecal cholesterol and bile acid levels were significantly (P<0.05) increased after LAB administration. Fecal lactobacilli counts were significantly (P<0.05) higher in the LAB treatment groups than in the control groups. Furthermore, the 3 strains were detected in the rat small intestine, colon and feces during the feeding trial. The bacteria levels remained high even after the LAB administration had been stopped for 2 weeks. These results suggest that these strains may be used in the future as probiotic starter cultures for manufacturing novel fermented foods.

Lactobacillus plantarum strains as potential probiotic cultures with cholesterol-lowering activity

Elevated blood cholesterol is an important risk factor associated with atherosclerosis and coronary heart disease. The search for mediators that fine-tune cholesterol homeostasis has revealed lactic acid bacteria (LAB) to be potentially beneficial. The aim of the present study was to identify and characterize probiotic strains with bile salt hydrolase activity from kefir grains and evaluate their potential use as cholesterol-reducing probiotics in rats. Two isolates, Lp09 and Lp45, obtained from kefir grains were identified as Lactobacillus plantarum via molecular typing methods. Lactobacillus plantarum Lp09 and Lp45 exhibited excellent tolerance to low pH levels and high bile salt concentrations and showed potential bile salt hydrolase activity, bile salt deconjugation activity, and cholesterol coprecipitation ability. Additionally, the potential effect of Lb. plantarum Lp09 and Lp45 on plasma cholesterol levels was evaluated in Sprague-Dawley rats. Rats in 3 treatment groups were fed different experimental diets: a high-cholesterol diet, a high-cholesterol diet plus Lb. plantarum Lp09, or a high-cholesterol diet plus Lb. plantarum Lp45 for 4 wk. Total cholesterol, triglyceride, and low-density lipoprotein cholesterol levels in serum as well as cholesterol and triglyceride levels in liver were significantly decreased in the LAB-treated rats compared with rats fed a high-cholesterol diet without LAB supplementation. Also, both fecal cholesterol and bile acid levels were significantly increased after LAB administration. No significant changes were detected in high-density lipoprotein cholesterol levels. These results suggest that the Lb. plantarum Lp09 and Lp45 strains present the potential to be explored as probiotic agents for the management of hypercholesterolemia.

Bile Salt Hydrolase (Bsh) Activity Screening of Lactobacilli: In Vitro Selection of Indigenous Lactobacillus Strains with Potential Bile Salt Hydrolysing and Cholesterol-Lowering Ability

The bile salt hydrolase (Bsh) activity of probiotic bacterium residing in gastrointestinal tract has often being associated with its cholesterol-lowering effects. Hence, Bsh activity was explored in this study as the criterion for the selection of most potential Bsh-active and cholesterol-lowering indigenous Lactobacillus strains. Forty lactobacilli were adjudged Bsh active after a preliminary screening of 102 lactobacilli and occurrence of Bsh activity correlated well with their natural habitats. Of the 40 shortlisted lactobacilli, fifteen putative Lactobacillus strains were selected and further tested for their comparative Bsh activity. In the end, indigenous Lactobacillus plantarum strains Lp91 and Lp21 were emerged as the promising Bsh-active lactobacilli with their substrate preference inclined more towards glycocholate than other bile acid amino conjugates. In addition, strains Lp91 and Lp21 also exhibited significantly high bile salt deconjugation, cholesterol assimilation and cholesterol co-precipitation ability in vitro. In conclusion, indigenous L. plantarum strains Lp91 and Lp21 may be the promising candidate probiotics to elucidate the ecological significance of probiotic Bsh activity in vivo.

Cholesterol-Lowering Probiotics as Potential Biotherapeutics for Metabolic Diseases

Cardiovascular diseases are one of the major causes of deaths in adults in the western world. Elevated levels of certain blood lipids have been reported to be the principal cause of cardiovascular disease and other disabilities in developed countries. Several animal and clinical trials have shown a positive association between cholesterol levels and the risks of coronary heart disease. Current dietary strategies for the prevention of cardiovascular disease advocate adherence to low-fat/low-saturated-fat diets. Although there is no doubt that, in experimental conditions, low-fat diets offer an effective means of reducing blood cholesterol concentrations on a population basis, these appear to be less effective, largely due to poor compliance, attributed to low palatability and acceptability of these diets to the consumers. Due to the low consumer compliance, attempts have been made to identify other dietary components that can reduce blood cholesterol levels. Supplementation of diet with fermented dairy products or lactic acid bacteria containing dairy products has shown the potential to reduce serum cholesterol levels. Various approaches have been used to alleviate this issue, including the use of probiotics, especially Bifidobacterium spp. and Lactobacillus spp.. Probiotics, the living microorganisms that confer health benefits on the host when administered in adequate amounts, have received much attention on their proclaimed health benefits which include improvement in lactose intolerance, increase in natural resistance to infectious disease in gastrointestinal tract, suppression of cancer, antidiabetic, reduction in serum cholesterol level, and improved digestion. In addition, there are numerous reports on cholesterol removal ability of probiotics and their hypocholesterolemic effects. Several possible mechanisms for cholesterol removal by probiotics are assimilation of cholesterol by growing cells, binding of cholesterol to cellular surface, incorporation of cholesterol into the cellular membrane, deconjugation of bile via bile salt hydrolase, coprecipitation of cholesterol with deconjugated bile, binding action of bile by fibre, and production of short-chain fatty acids by oligosaccharides. The present paper reviews the mechanisms of action of anti-cholesterolemic potential of probiotic microorganisms and probiotic food products, with the aim of lowering the risks of cardiovascular and coronary heart diseases.

Characterisation of Lactobacillus fermentum SM-7 isolated from koumiss, a potential probiotic bacterium with cholesterol-lowering effects

Lactic acid bacteria (LAB) have been demonstrated to have cholesterol-reducing effects in many studies. Lactobacillus fermentum SM-7 screened from ten LAB strains isolated from koumiss, a fermented milk drink, reduced cholesterol by 66.8%. It also showed acid and bile tolerance as well as antimicrobial activity against pathogenic Escherchia coli and Staphylococcus aureus. Lactobacillus fermentum SM-7 cells assimilated 61.5% and co-precipitated and absorbed 38.5% of the cholesterol in the media. Co-precipitation of cholesterol with cholic acid increased rapidly at pH levels below 6. In vivo experiments using L. fermentum SM-7 on artificially induced hyperlipidaemial ICR mice significantly decreased serum total cholesterol and total triglyceride levels, low-density lipoprotein cholesterol concentrations and atherogenic index (P < 0.01), while serum high-density lipoprotein cholesterol concentrations did not increase significantly (P > 0.05). The body weight and liver weight/body weight ratio of SM-7 groups were lower than those of mice on a high-cholesterol diet that were not given lactobacilli. There was no bacterial translocation in the liver, spleen or kidney of experimental mice. The results suggested that L. fermentum SM-7 is a potential probiotic bacterium with cholesterol-lowering effects.

Hypocholesterolaemic effect of dietary inclusion of two putative probiotic bile salt hydrolase-producingLactobacillus plantarumstrains in Sprague–Dawley rats

The purpose of the present study was to evaluate the anti-hypercholesterolaemic effects of two putative probiotic bile salt hydrolase (Bsh)-producing Lactobacillus plantarum strains, i.e. Lp91 and Lp21, in rats. L. plantarum Lp91 exhibited excellent tolerance to low pH and high bile salt concentrations as well as showed potential Bsh activity, cholesterol assimilation and cholesterol co-precipitation ability along with L. plantarum Lp21 and NCDO82 strains. Furthermore, the potential effect of L. plantarum Lp91 on plasma cholesterol level was evaluated in Sprague-Dawley rats. Five treatment groups of rats (n 6) were fed experimental diets: normal diet, hypercholesterolaemic diet (HD), HD plus L. plantarum Lp91 (HD91) at≥1·0×108 colony-forming units (cfu)/g, HD plus microencapsulated L. plantarum Lp91 (HDCap91) at≥1·0×108cfu/g and HD plus L. plantarum Lp21 (HD21) at≥1·0×108cfu/g for 3 weeks. Feed intake and feed efficiency differed significantly among the five groups. After 21d of dietary treatment, comparative analysis revealed 23·26, 15·71 and 15·01% reduction in total cholesterol, 21·09, 18·77 and 18·17% reduction in TAG, 38·13, 23·22 and 21·42% reduction in LDL-cholesterol, and the corresponding HDL-cholesterol values increased at the rate of 18·94, 10·30 and 7·78% in treated groups HD91, HDCap91 and HD21, respectively. Faecal excretion of cholic acid and faecal lactobacilli counts were significantly higher in the probiotic treatment groups than in the control groups. In conclusion, these results suggest that the indigenous L. plantarum Lp91 strain has the potential to be explored as a probiotic in the management of hypercholesterolaemia.

A BSH volumetric activity dependent method for determination of coprecipitated cholesterol and the assimilation/coprecipitation proportion of cholesterol removal byLactobacillus plantarum

Thein vitro removal of cholesterol by probiotics has been categorized into two phases: assimilation by bacterial cells, and coprecipitation with deconjugated bile salts. Bile salt hydrolase (BSH) produced by probiotics catalyzes the deconjugation reaction of bile salts. A novel method that depends on the BSH volumetric activity (μg min−1 ml−1 bacteria culture) was developed to evaluate the cholesterol coprecipitation in MRS culture supplemented with synthetic human bile and cholesterol. Six probioticLactobacillus plantarum strains from the healthy youth intestinal tract were screened. The amount of cholesterol coprecipitation that occurred in eachL. Plantarum culture was then determined according to the method developed here and verified by a modified redissolution method. Next, the assimilation/coprecipitation proportion of cholesterol removal for each strain was deduced. The results revealed that after 12 h of incubation, all six strains ofL. plantarum removed a larger amount of cholesterol by assimilation (63.45–81.62%) than by coprecipitation (18.38–36.55%). Finally, we investigated the effects of synthetic human bile on BSH specific activity (μg min−1 mg−1 protein) and found that the BSH specific activity of all strains showed a rapid, limited and reversible decrease in response to synthetic human bile stress. We also found that variations in the BSH specific activity were related to the growth phases and that the maximum emerged after approximately 8 h (middle exponential phase) of growth.

Epigenetic Effectiveness of Complete Carcinogens: Specific Interactions of Polycyclic Aromatic Hydrocarbons and Aminoazo Dyes with Cholesterol and Apolipoprotein A-I

During a co-precipitation of cholesterol (Chol) and slight amounts of polycyclic aromatic hydrocarbons (PAHs) or aminoazo dyes (AZOs) in aqueous albumin solution, complex particles are formed; on their surfaces apolipoproteins with an amphipathic alpha-helix (e.g. apoA-I) are more or less firmly adsorbed. An efficacy index can be calculated from the strength of the hydrophobic interactions between apoA-I and the [Chol/PAH]- or [Chol/AZO]-complex, and the solubility of the PAH or AZO in an aqueous medium, which correlates to the carcinogenicity of these compounds. A short-term test for PAHs and AZOs is described, in which the efficacy index can be determined in the simplest manner without any great expenditure on equipment. The previous results suggest that the parent compounds of the PAHs and AZOs can be involved in a specific interaction with cholesterol-domains of the plasma membrane of a cell. The changes in membrane fluidity and architecture caused by these specific interactions could modulate the distribution and/or activity of membrane proteins which are critical to the regulation of cellular proliferation.

Operating regimes and mechanism of particle formation during the precipitation of polymers using the PCA process

The vapour–liquid equilibrium phase behavior of a solvent and carbon dioxide provides two different regions of operation for the precipitation with a compressed antisolvent (PCA) process. Below the critical pressure of the mixture there is an interface between the liquid- and vapour-phase. Solution droplets are formed by atomisation in the nozzle. Above the critical- (or saturation-) pressure there is no phase boundary and contact between CO 2 and solution takes place by mixing. Additionally, in both operating regions, droplets of a polymer rich-phase are formed as result of a liquid–liquid phase split induced in the polymer solution when it gets in contact with the CO 2. This article provides experimental evidence for the hypothesis that when processing polymer solutions there are two different mechanisms of droplet formation governing the final size of the precipitated polymer particles: hydraulic atomisation and liquid–liquid phase split. The system l-polylactic acid ( l-PLA)–dichloromethane (DCM)–CO 2 was used to demonstrate that particle size can be manipulated by modifying the operating conditions. Working at conditions below the mixture critical pressure of the solvent–CO 2 mixture it was possible to produce polymer particles in the range of 5–50 μm. At conditions where the two fluids are completely miscible, l-PLA particles ranging from 0.1 to 2 μm and microfibers were obtained. The possibility of co-precipitation of cholesterol and l-PLA was also addressed.

Bile salt deconjugation ability, bile salt hydrolase activity and cholesterol co-precipitation ability of lactobacilli strains

Eleven strains of lactobacilli were screened for their bile salt deconjugation ability, bile salt hydrolase activity (BSH) and co-precipitation of cholesterol with deconjugated bile. Bile salt deconjugation as determined by the release of cholic acid showed that more cholic acid was liberated from the deconjugation of sodium glycocholate than sodium taurocholate, and Lactobacillus acidophilus strains had higher deconjugation ability than L. casei strains. BSH activity, as quantified by the amount of taurine or glycine liberated from conjugated bile salts, indicated that substrate specificity was more towards glycine-conjugated bile compared to taurine-conjugated bile. Co-precipitation of cholesterol with cholic acid was observed from deconjugation of both conjugated bile, with more cholesterol being precipitated upon deconjugation of sodium glycocholate than upon that of sodium taurocholate. Cholesterol co-precipitation with deconjugated bile increased with decreasing pH. L. acidophilus ATCC 33200, 4356 and 4962 and L. casei ASCC 1521 showed highest deconjugation ability and BSH activity towards bile mixtures that resemble the human bile, and may be promising candidates to exert beneficial bile deconjugation activity in vivo.

Bile salt deconjugation and BSH activity of five bifidobacterial strains and their cholesterol co-precipitating properties

Five strains of bifidobacteria were screened for their bile salt deconjugation ability, bile salt hydrolase (BSH) activity and co-precipitation of cholesterol with deconjugated bile. Bile salt deconjugation was determined by the release of cholic acid. All strains exhibited deconjugation of both sodium glycocholate and sodium taurocholate. More cholic acid was liberated from the deconjugation of sodium glycocholate than sodium taurocholate. BSH activity was quantified by determining the amount of glycine or taurine liberated from conjugated bile salts by bifidobacteria strains. There was higher substrate specificity for glycine-conjugated bile compared to taurine-conjugated bile. Co-precipitation of cholesterol with cholic acid was observed from deconjugation of both sodium glycocholate and sodium taurocholate, and by all bifidobacteria strains studied. More cholesterol was precipitated with cholic acid when sodium glycocholate was used compared to sodium taurocholate. Increased cholesterol co-precipitation with deconjugated bile was observed with decreasing pH levels. Bifidobacterium infantis 17930 showed highest deconjugation ability and BSH activity towards bile mixtures that resemble the human bile, and may be a promising candidate to exert beneficial bile deconjugation activity in vivo.

The assumed assimilation of cholesterol by Lactobacilli and Bifidobacterium bifidum is due to their bile salt-deconjugating activity.

To study the mechanism of the propsed assimilation of cholesterol, we cultured various strains of Lactobacillus acidophilus and a Bifidobacterium sp. in the presence of cholesterol and oxgall. During culturing, both cholesterol and bile salts were precipitated. Because of bacterial bile salt deconjugation, no conjugated bile salts were observed in either the culture fluids or the pellets. During incubation, the cell count and optical density decreased. The degree of precipitation of bile salts and of cholesterol was dependent on the culture conditions. If L. acidophilus RP32 was cultured under acidifying conditions, the degree of precipitation of deconjugated bile salts was higher than if the pH was maintained at 6.0. Under acidifying conditions, cholesterol was coprecipitated with the bile salts, whereas in pH-controlled cultures, no coprecipitation of cholesterol was observed. From control experiments with different mixtures of bile salts, it appeared that coprecipitation of cholesterol during culturing was a result of formation of deconjugated bile salts, which have a decreased solubility at pH values lower than 6.0. It is concluded that the removal of cholesterol from the culture medium by L. acidophilus RP32 and other species is not due to bacterial uptake of cholesterol, but results from bacterial bile salt-deconjugating activity.