Production of exopolysaccharides by Lactobacillus and Bifidobacterium strains of human origin, and metabolic activity of the producing bacteria in milk

This work reports on the physicochemical characterization of 21 exopolysaccharides (EPS) produced by Lactobacillus and Bifidobacterium strains isolated from human intestinal microbiota, as well as the growth and metabolic activity of the EPS-producing strains in milk. The strains belong to the species Lactobacillus casei, Lactobacillus rhamnosus, Lactobacillus plantarum, Lactobacillus vaginalis, Bifidobacterium animalis, Bifidobacterium longum, and Bifidobacterium pseudocatenulatum. The molar mass distribution of EPS fractions showed 2 peaks of different sizes, which is a feature shared with some EPS from bacteria of food origin. In general, we detected an association between the EPS size distribution and the EPS-producing species, although because of the low numbers of human bacterial EPS tested, we could not conclusively establish a correlation. The main monosaccharide components of the EPS under study were glucose, galactose, and rhamnose, which are the same as those found in food polymers; however, the rhamnose and glucose ratios was generally higher than the galactose ratio in our human bacterial EPS. All EPS-producing strains were able to grow and acidify milk; most lactobacilli produced lactic acid as the main metabolite. The lactic acid-to-acetic acid ratio in bifidobacteria was 0.7, close to the theoretical ratio, indicating that the EPS-producing strains did not produce an excessive amount of acetic acid, which could adversely affect the sensory properties of fermented milks. With respect to their viscosity-intensifying ability, L. plantarum H2 and L. rhamnosus E41 and E43R were able to increase the viscosity of stirred, fermented milks to a similar extent as the EPS-producing Streptococcus thermophilus strain used as a positive control. Therefore, these human EPS-producing bacteria could be used as adjuncts in mixed cultures for the formulation of functional foods if probiotic characteristics could be demonstrated. This is the first article reporting the physicochemical characteristics of EPS isolated from human intestinal microbiota.     

Sensory and rheological screening of exopolysaccharide producing strains of bacterial yoghurt cultures

Yoghurts were produced with 24 different cultures differing in their ability to produce exopolysaccharides (EPS). Rheological and sensory analyses showed large differences in texture properties in the yoghurt samples. EPS production was found to have a major effect on the texture properties, but varying textures within the EPS±groups were also found. Yoghurts fermented with EPS-producing cultures showed increased mouth thickness and ropiness and tended to be creamier than yoghurts without these cultures; in contrast, these yoghurts had the lowest syneresis and highest gel firmness (initial gel strength before the yoghurt was subjected to shear). Correlations between rheological parameters and sensory texture attributes included G* correlating with gel firmness, while viscosity measured at 241 s⁻¹ correlated with mouth thickness. An interesting viscometry relationship was found between ropiness and hysteresis loop area.     

Observation of bacterial exopolysaccharide in dairy products using cryo-scanning electron microscopy

Cryo-scanning electron microscopy was used to visualize the microstructure of two types of cheese (Karish and Feta) and milk fermented with different ropy and non-ropy strains of lactic acid bacteria. Specimen frozen in liquid nitrogen slush were transferred in a frozen state and under vacuum into the preparation chamber where they were fractured, etched and coated with gold. Specimen were then transferred under vacuum onto the cold stage and imaged using scanning electron microscopy (SEM). Milk fat and exopolysaccharide (EPS) were visible in pores within the protein network. Cheese and fermented milk made with EPS-producing cultures exhibited a porous structure in which the largest pores were associated with visible EPS. A compact structure with small pores was seen in cheese and milk fermented with EPS non-producing cultures. EPS and protein appeared to be segregated in both cheese and fermented milk. EPS formed a network-like structure. Differences were observed in the microstructure of EPS between moderately ropy and highly ropy strains. A relatively long etching (sublimation) time caused EPS to appear as thin filaments similar to those seen with conventional SEM.     

Ultrafiltered milk reduces bitterness in reduced-fat Cheddar cheese made with an exopolysaccharide-producing culture

The objectives were to reduce bitterness in reduced-fat Cheddar cheese made with an exopolysaccharide (EPS)-producing culture and study relationships among ultra-filtration (UF), residual chymosin activity (RCA), and cheese bitterness. In previous studies, EPS-producing cultures improved the textural, melting, and viscoelastic properties of reduced-fat Cheddar cheese. However, the EPS-positive cheese developed bitterness after 2 to 3 mo of ripening due to increased RCA. We hypothesized that the reduced amount of chymosin needed to coagulate UF milk might result in reduced RCA and bitterness in cheese. Reduced-fat Cheddar cheeses were manufactured with EPS-producing and nonproducing cultures using skim milk or UF milk (1.2×) adjusted to a casein:fat ratio of 1.35. The EPS-producing culture increased moisture and RCA in reduced-fat Cheddar cheese. Lower RCA was found in cheese made from UF milk compared with that in cheese made from control milk. Ultrafiltration at a low concentration rate (1.2×) produced EPS-positive, reduced-fat cheese with similar RCA to that in the EPS-negative cheese. Slower proteolysis was observed in UF cheeses compared with non-UF cheeses. Panelists reported that UF EPS-positive cheese was less bitter than EPS-positive cheese made from control milk. This study showed that UF at a low concentration factor (1.2×) could successfully reduce bitterness in cheese containing a high moisture level. Because this technology reduced the RCA level (per g of protein) to a level similar to that in the control cheeses, the contribution of chymosin to cheese proteolysis would be similar in both cheeses.     

Contribution of Streptococcus thermophilus to growth-stimulating effect of yogurt on rats

The origin of the growth-stimulating factor in yogurt was studied in rats fed liquid or freeze-dried diets of milk, yogurt, milks fermented individually by Streptococcus thermophilus and Lactobacillus bulgaricus, milks to which cells of Streptococcus thermophilus and Lactobacillus bulgaricus were added. Diets containing sonicated cells, cell supernatant, and cell fractions also were fed. Milk fermented by Streptococcus thermophilus and milk plus Streptococcus thermophilus cells stimulated growth as effectively as did yogurt. That finding and the absence of stimulation in rats fed Lactobacillus bulgaricus showed that Streptococcus thermophilus is responsible for stimulation of growth by yogurt. Growth was stimulated by an intracellular factor and not by fermentative changes in the milk.     

Color of Nonfat Fluid Milk as Affected by Fermentation

Nonfat milks inoculated and fermented with exopolysaccharide and non-exopolysaccharide producing cultures were compared to nonfat, 2% milkfat and whole milk with instrumental and sensory color measurements. L-(whiteness) and a- values (red/greeness) for fermented nonfat milks were higher than nonfat milk. No differences in L-, a-, or b- values (yellow/blueness) were found between milks fermented with exopolysaccharide as compared to non-exopolysaccharide producing strains. A trained sensory panel scored edge and center whiteness of fermented milks whiterthan nonfat milk. Milks fermented with exopolysaccharide producing cultures were scored higher than non-exopolysaccharide producing cultures with respect to edge and center whiteness. Fermentation and exopolysaccharide production may increase visual perception of whiteness in milk.     

ADSA Foundation Scholar Award: Possibilities and challenges of exopolysaccharide-producing lactic cultures in dairy foods

Exopolysaccharides (EPS) from lactic acid bacteria are a diverse group of polysaccharides exhibiting various functional properties. Two forms of EPS are produced by lactic acid bacteria: capsular and unattached. Capsular EPS does not cause ropiness nor does production of unattached EPS ensure ropiness. The functions of EPS in dairy products are not completely understood. This is for 2 main reasons: the major variations among exopolysaccharides even from the same group of micro-organisms, which makes it difficult to apply information from one EPS to others, and the lack of availability of techniques with the ability to observe the microstructure and distribution of the highly hydrated EPS in fermented dairy products. The introduction of relatively new microscopic techniques such as confocal scanning laser microscopy and cryo-scanning electron microscopy made it possible to directly observe the distribution of fully hydrated EPS in dairy products. Recently, EPS produced by nonropy strains have drawn the attention of the dairy industry. This is because of the ability of some nonropy strains to produce large capsular and unattached EPS that would improve the texture of dairy products without causing the undesirable slippery mouthfeel produced by the ropy strains. Factors affecting functions of EPS are their molecular characteristics and ability to interact with milk proteins. Studying the interaction between EPS and milk proteins is complex because EPS are gradually produced during fermentation, unlike polysaccharides added directly to milk to stabilize the fermented product. The concentration and possibly molecular characteristics of EPS and protein characteristics such as charge and hydrophobicity change during fermentation. Consequently, the interaction of EPS with proteins might also change during fermentation. Exopolysaccharides provide functions that benefit reduced-fat cheeses. They bind water and increase the moisture in the nonfat portion, interfere with protein-protein interactions and reduce the rigidity of the protein network, and increase viscosity of the serum phase. This review discusses the production of capsular EPS and their role in structure formation in fermented milk, the mechanism of ropiness formation, and applications of EPS-producing cultures in reduced-fat cheeses.     

Ingestion of milk fermented by genetically modified Lactococcus lactis improves the riboflavin status of deficient rats

Riboflavin deficiency is common in many parts of the world, particularly in developing countries. The use of riboflavin-producing strains in the production of dairy products such as fermented milks, yogurts, and cheeses is feasible and economically attractive because it would decrease the costs involved during conventional vitamin fortification and satisfy consumer demands for healthier foods. The present study was conducted to assess in a rat bioassay the response of administration of milk fermented by modified Lactococcus lactis on the riboflavin status of deficient rats. Rats were fed a riboflavin-deficient diet during 21 d after which this same diet was supplemented with milk fermented by Lactoccus lactis pNZGBAH, a strain that overproduces riboflavin during fermentation. The novel fermented product, with increased levels of riboflavin, was able to eliminate most physiological manifestations of ariboflavinosis, such as stunted growth, elevated erythrocyte glutathione reductase activation coefficient values and hepatomegaly, that were observed using a riboflavin depletion-repletion model, whereas a product fermented with a nonriboflavin-producing strain did not show similar results. A safety assessment of this modified strain was performed by feeding rodents with the modified strain daily for 4 wk. This strain caused no detectable secondary effects. These results pave the way for analyzing the effect of similar riboflavin-overproducing lactic acid bacteria in human trials. The regular consumption of products with increased levels of riboflavin could help prevent deficiencies of this essential vitamin.     

Comparison of the functionality of exopolysaccharides produced in situ or added as bioingredients on yogurt properties

The effect on yogurt properties of in situ production of exopolysaccharides (EPS) and addition of 2 EPS powders (crude and purified EPS from Lactobacillus rhamnosus RW-9595M fermentation in whey-based medium) at different concentrations was studied. No effect of purified powder addition for EPS concentrations up to 500 mg/L was observed on acidification rate to the difference of milks supplemented with crude EPS, which exhibited longer acidification times. The addition of EPS from 125 to 500 mg/L or the use of EPS-producing cultures resulted in yogurts with lower yield stress and viscoelastic moduli compared with control yogurts without EPS, with no apparent effect of EPS concentration. However, the consistency index was higher for yogurts produced with the commercial EPS-producing culture, and to a lesser extent with the mixed culture containing Lb. rhamnosus RW-9595M, compared with yogurts supplemented with EPS powders, which were not different from that for control yogurts. Our study showed that the mode of EPS incorporation in yogurts has a major effect on the rheological properties of the final product.     

Effect of buckwheat flour and oat bran on growth and cell viability of the probiotic strains Lactobacillus rhamnosus IMC 501®, Lactobacillus paracasei IMC 502® and their combination SYNBIO®, in synbiotic fermented milk

Fermented foods have a great significance since they provide and preserve large quantities of nutritious foods in a wide diversity of flavors, aromas and texture, which enrich the human diet. Originally fermented milks were developed as a means of preserving nutrients and are the most representatives of the category. The first aim of this study was to screen the effect of buckwheat flour and oat bran as prebiotics on the production of probiotic fiber-enriched fermented milks, by investigating the kinetics of acidification of buckwheat flour- and oat bran-supplemented milk fermented by Lactobacillus rhamnosus IMC 501®, Lactobacillus paracasei IMC 502® and their 1:1 combination named SYNBIO®. The probiotic strains viability, pH and sensory characteristics of the fermented fiber-enriched milk products, stored at 4 °C for 28 days were also monitored. The results showed that supplementation of whole milk with the tested probiotic strains and the two vegetable substrates results in a significant faster lowering of the pH. Also, the stability of L. rhamnosus IMC 501®, L. paracasei IMC 502® and SYNBIO® during storage at 4 °C for 28 days in buckwheat flour- and oat bran-supplemented samples was remarkably enhanced. The second aim of the study was to develop a new synbiotic product using the best combination of probiotics and prebiotics by promoting better growth and survival and be acceptable to the consumers with high concentration of probiotic strain. This new product was used to conduct a human feeding trial to validate the fermented milk as a carrier for transporting bacterial cells into the human gastrointestinal tract. The probiotic strains were recovered from fecal samples in 40 out of 40 volunteers fed for 4 weeks one portion per day of synbiotic fermented milk carrying about 10⁹ viable cells.     

EFFECT OF HIGH HYDROSTATIC PRESSURE PROCESSING ON RHEOLOGICAL AND TEXTURAL PROPERTIES OF PROBIOTIC LOW-FAT YOGURT FERMENTED BY DIFFERENT STARTER CULTURES

The effect of milk processing on rheological and textural properties of probiotic low‐fat yogurt (fermented by two different starter cultures) was studied. Skim milk fortified with skim milk powder was subjected to three treatments: (1) thermal treatment at 85C for 30 min; (2) high hydrostatic pressure (HHP) at 676 MPa for 5 min; and (3) combined treatments of HHP (676 MPa for 5 min) and heat (85C for 30 min). The processed milk was fermented using two different starter cultures containing Streptococcus thermophilus, Lactobacillus delbrueckii ssp. bulgaricus, Lactobacillus acidophilus and Bifidobacterium longum at inoculation rates of 0.1 and 0.2%. Rheological parameters were determined and a texture profile analysis was carried out. Yogurts presented different rheological behaviors according to the treatment used, which could be attributed to structural phenomena. The combined HHP and heat treatment of milks resulted in yogurt gels with higher consistency index values than gels obtained from thermally treated milk. The type of starter culture and inoculation rate, providing different fermentation pathways, also affected the consistency index and textural properties significantly. The combined HHP and heat treatment of milks before fermentation, and an inoculation rate of 0.1% (for both cultures), led to desirable rheological and textural properties in yogurt, which presented a creamy and thick consistency that does not require the addition of stabilizers.     

Metabolomic profile of milk fermented with Streptococcus thermophilus cocultured with Bifidobacterium animalis ssp. lactis,Lactiplantibacillus plantarum,or both during storage

In this study, the microbial interactions among cocultures of Streptococcus thermophilus (St) with potential probiotics of Bifidobacterium animalis ssp. lactis (Ba) and Lactiplantibacillus plantarum (Lp) in fermented milk were investigated during a storage period of 21 d at 4°C, in terms of acidifying activity (pH and titratable acidity), viable counts, and metabolites. A nontargeted metabolomics approach based on ultra-high-performance liquid chromatography coupled with mass spectrometry was employed for mapping the global metabolite profiles of fermented milk. Probiotic strains cocultured with St accelerated milk acidification, and improved the microbial viability compared with the single culture of St. The St–Ba/Lp treatment manifested a higher bacteria viability and acidification ability in comparison with the St–Ba or the St–Lp treatment. Relative quantitation of 179 significant metabolites was identified, including nucleosides, AA, short peptides, organic acids, lipid derivatives, carbohydrates, carbonyl compounds, and compounds related to energy metabolism. The principal component analysis indicated that St treatment and coculture treatments displayed a complete distinction in metabolite profiles, and Lp had a larger effect than Ba on metabolic profiles of fermented milk produced by cofermentation with St during storage. The heat map in combination with hierarchical cluster analysis showed that the abundance of metabolites significantly varied with the starter cultures over the storage, and high abundance of metabolites was observed in either St or coculture samples. The St-Ba/Lp treatment showed relatively high abundance for the vast majority of metabolites. These findings suggest that the profile of the metabolites characterizing fermented milk samples may depend on the starter cultures, and incorporation of probiotics may considerably influence the metabolomic activities of fermented milks.     

Impact of ropy and capsular exopolysaccharide-producing strains of Lactococcus lactis subsp. cremoris on reduced-fat Cheddar cheese production and whey composition

Cheddar cheese mixed starter cultures containing exopolysaccharide (EPS)-producing strains of Lactococcus lactis subsp. cremoris (Lac. cremoris) were characterized and used for the production of reduced-fat Cheddar cheese (15% fat). The effects of ropy and capsular strains and their combination on cheese production and physical characteristics as well as composition of the resultant whey samples were investigated and compared with the impact of adding 0.2% (w/v) of lecithin, as a thickening agent, to cheese milk. Control cheese was made using EPS-non-producing Lac. cremoris. Cheeses made with capsular or ropy strains or their combination retained 3.6–4.8% more moisture and resulted in 0.29–1.19 kg/100 kg higher yield than control cheese. Lecithin also increased the moisture retention and cheese yield by 1.4% and 0.37%, respectively, over the control cheese. Lecithin addition also substantially increased viscosity, total solid content and concentrating time by ultra-filtration (UF) of the whey produced. Compared with lecithin addition, the application of EPS-producing strains increased the viscosity of the resultant whey slightly, while decreasing whey total solids, and prolonging the time required to concentrate whey samples by UF. The amount of EPS expelled in whey ranged from 31 to 53 mg L⁻¹. Retention of EPS-producing strains in cheese curd was remarkably higher than that of non-producing strains. These results indicate the capacity of EPS-producing Lac. cremoris for enhanced moisture retention in reduced-fat Cheddar cheese; these strains would be a promising alternative to commercial stabilizers.     

Enhancement of functional characteristics of mixed lactic culture producing nisin z and exopolysaccharides during continuous prefermentation of milk with immobilized cells

Antagonistic phenomena between strains often occur in mixed cultures containing a bacteriocinogenic strain. A nisin Z producer (Lactococcus lactis ssp. lactis biovar. diacetylactis UL719) and 2 nisin-sensitive strains for acidification (Lactococcus lactis ssp. cremoris ATCC19257) and exopolysaccharide (EPS) production (Lactobacillus rhamnosus RW-9595M) were immobilized separately in gel beads and used to continuously preferment milk at different temperatures, with pH controlled at 6.0 by fresh milk addition. The process showed high volumetric productivity, with an increase from 8.0 to 12.5 L of prefermented milk per liter of reactor volume and hour as the temperature was increased from 27 to 35°C. Lactococcus lactis ssp. lactis biovar. diacetylactis UL719 counts in prefermented and fermented (22-h batch fermentation) milks were stable during 3 wk of continuous fermentation (8.1 ± 0.1 and 8.9 ± 0.2 log cfu/mL, respectively). The L. lactis ssp. cremoris population (estimated with real-time quantitative PCR) decreased rapidly during the first week of continuous culture to approximately 4.5 log cfu/mL and remained constant afterward. Lactobacillus rhamnosus counts in prefermented and fermented milks significantly increased with prefermentation time, with no temperature effect. Nisin Z reached high titers in fermented milks (from 177 to 363 IU/mL), with EPS concentration in the range from 43 to 178 mg/L. Immobilization and continuous culture led to important physiological changes, with Lb. rhamnosus becoming much more tolerant to nisin Z, and Lb. rhamnosus and L. lactis ssp. lactis biovar. diacetylactis UL719 exhibiting large increases in milk acidification capacity. Our data showed that continuous milk prefermentation with immobilized cells can stimulate the acidification activity of low-acidifying strains and produce fermented milks with improved and controlled functional properties.     

Prevention of chronic gastritis by fermented milks made with exopolysaccharide-producing Streptococcus thermophilus strains

Acetyl-salicylic acid (ASA) is a nonsteroidal antiinflammatory/analgesic drug, which may cause gastritis or stomach ulcers if intensively employed. Exopolysaccharide (EPS)-producing lactic acid bacteria have been claimed to induce immunostimulatory/antiulcer effects in the host. This study investigated the potential preventive effect of fermented milks (FM) with EPS-producing Streptococcus thermophilus strains (CRL 1190 and CRL 804) on an in vivo model of chronic gastritis. Fermented milks (2 EPS⁺ and 1 EPS⁻, separately) were fed to BALB/c mice for 7 d before inducing gastritis with ASA (400 mg/kg of body weight per day for 10 d; gastritis group, n = 5). Appropriate control groups (ASA administered but not given FM, n = 5; and ASA not administered but given FM) were included in this study. Gastric inflammatory activity was evaluated through the stomach's histology and the number of IFNγ⁺ and IL-10⁺ cytokine-producing cells in the gastric mucosa. Only mice preventively treated with the EPS-producing Strep. thermophilus CRL 1190 FM and later administered ASA did not develop gastritis, showing a conserved gastric mucosa structure similar to those of healthy mice. A marked decrease of IFNγ⁺- and increase of IL-10⁺-producing cells compared with the gastritis group mice were observed. Purified EPS from Strep. thermophilus CRL 1190 resuspended in autoclaved milk was also effective for gastritis prevention. The EPS-protein interaction might be responsible for the observed gastroprotective effect; such interactions may be affected by industrial manufacturing conditions. The results indicate that the FM with Strep. thermophilus CRL 1190 or its EPS could be used in novel functional foods for preventing chronic gastritis.     

Effect of milk supplementation and culture composition on acidification, textural properties and microbiological stability of fermented milks containing probiotic bacteria

In the present work, the combined effect of milk supplementation and culture composition on acidification, textural properties, and microbiological stability of fermented milks containing probiotic bacteria, was studied. Three powders (whey, casein hydrolysate, and milk proteins) were tested as supplementation. Two strains of probiotic bacteria, Lactobacillus acidophilus (LA5) and Lactobacillus rhamnosus (LC35), were used in pure culture, and in mixed culture with Streptococcus thermophilus (ST7). Acidifying activity was enhanced with mixed cultures, compared to pure cultures resulting in a shorter time to reach pH 4.5. Acidifying activity was greatly improved with casein hydrolysate, with a reduction of the fermentation time by about 55% by comparison with the other supplementations. The stability of probiotic bacteria was weakly affected by milk supplementation and culture composition. However, pure cultures were more stable than mixed cultures. The texture of the fermented products was not dependent on culture composition, but strongly dependent on milk supplementation. Sweet whey supplementation gave products with lower firmness and viscoelasticity than products supplemented with casein hydrolysate or milk proteins (decrease by 70%). It was observed that all products containing probiotic counts over 2.2×10⁷ CFU mL⁻¹ are suitable for the development of a lactic beverage containing probiotics.     

Physical properties and microstructure of yoghurts supplemented with milk protein hydrolysates

The physical properties and the microstructure of yoghurts containing probiotic bacteria, and supplemented with milk protein hydrolysates, were studied. Three casein hydrolysates and three whey protein hydrolysates were added to milk at a concentration ranging from 0.25 to 4 g L⁻¹. The milks were then fermented with either of two different cultures. The resulting yoghurts with added hydrolysates were compared to the control yoghurt without supplementation. For both cultures, addition of hydrolysates decreased the complex viscosity and graininess in yoghurts. The addition of hydrolysates also reduced fermentation time. Microstructural observations showed a more open and less branched structure in yoghurts when milk protein hydrolysates were incorporated. The difference in fermentation time between milks with different levels of added hydrolysates could partially explain the differences in microstructure and physical properties of the final yoghurts.     

Effect of high-pressure homogenization, nonfat milk solids, and milkfat on the technological performance of a functional strain for the production of probiotic fermented milks

The aim of this research was the evaluation of the effects of milkfat content, nonfat milk solids content, and high-pressure homogenization on 1) fermentation rates of the probiotic strain Lactobacillus paracasei BFE 5264 inoculated in milk; 2) viability loss of this strain during refrigerated storage; and 3) texture parameters, volatile compounds, and sensorial properties of the coagula obtained. The data achieved suggested a very strong effect of the independent variables on the measured attributes of fermented milks. In fact, the coagulation times were significantly affected by pressure and added milkfat, and the rheological parameters of the fermented milk increased with the pressure applied to the milk for added nonfat milk solids concentrations lower than 3%. Moreover, the polynomial models and the relative response surfaces obtained permitted us to identify the levels of the 3 independent variables that minimized the viability loss of the probiotic strain used during refrigerated storage.     

Effect of administration of Lactobacillus gasseri on serum lipids and fecal steroids in hypercholesterolemic rats

The effects of milk and nonfermented milks produced from Lactobacillus gasseri on serum lipids and total bile acids and fecal steroids and microflora were estimated in rats fed cholesterol-enriched diets. Lactobacilli decreased and coliforms increased in feces of the control group; however, the concentrations of fecal lactobacilli remained unchanged when rats were fed nonfermented milks. Fecal coliforms in rats receiving milk and nonfermented milk produced from L. gasseri SBT0270 increased, while rats receiving nonfermented milk produced from L. gasseri SBT0274 had lower fecal coliform count than did the control group. Only NFM-A significantly reduced serum total cholesterol and low-density lipoprotein (LDL) cholesterol, and bile acids. High-density lipoprotein (HDL) cholesterol was significantly decreased when rats were given milk and nonfermented milks. Milk and NFM-A lowered serum triglycerides levels. Milk and nonfermented milks did not affect the total neutral steroids, but higher levels of acidic steroid were detected in the feces than the control group. The results showed that the hypocholesterolemic effect of L. gasseri SBT0270 was attributed to its ability to suppress the reabsorption of bile acids into the enterohepatic circulation and to enhance the excretion of acidic steroids in feces of hypercholesterolemic rats.     

Cholesterol Lowering Activity of Ropy Fermented Milk

The effect of ropy fermented milk on serum cholesterol in rats was studied. Basic diets containing slime-forming Lactococcus lactis subsp. cremoris SBT 0495, its non slime-forming variant SBT 1275, and acidified reconstituted skim milk, with 0.5% cholesterol added, were fed to F-344 rats for 7 days. Serum cholesterol level of rats fed the ropy fermented milk were the lowest among the three treatments. The serum high-density lipoprotein (HDL) cholesterol/total cholesterol ratio of rats fed ropy fermented milk was the highest. Slime materials produced by L. lactis subsp. cremoris SBT 0495 had a beneficial effect on rat cholesterol metabolism.