Widely distributed lysogeny in probiotic lactobacilli represents a potentially high risk for the fermentative dairy industry

Prophages account for most of the genetic diversity among strains of a given bacterial species, and represent a latent source for the generation of virulent phages. In this work, a set of 30 commercial, collection and dairy-isolated Lactobacillus casei group strains were used. A species-specific PCR assay allowed a reclassification, mainly of strains previously considered Lactobacillus casei, into either Lactobacillus paracasei or Lactobacillus rhamnosus. All the strains were induced with mitomycin C, allowing direct recovering of phage DNA in 25 cases, which corroborates the widely occurrence of lysogeny on Lactobacillus genomes, including probiotic strains of Lactobacillus casei group. Ten out of 11 commercial strains studied contained prophages, evidencing the potential risks of their use at industrial scale. Strains were also induced by treatment with different concentrations of hydrogen peroxide but, however, this agent was not able to evidence a prophage release for any of the strains tested. According to a RAPD-PCR fingerprinting with M13, 1254 and G1 primers, most of the commercial strains presented a high degree of homology and, regarding BglII- and BamHI-restriction profiles of phage DNA, six of them harboured the same prophage. Surprisingly, both Lactobacillus paracasei ATCC 27092 and Lactobacillus paracasei ATCC 27139 shared a second prophage with both an INLAIN collection and a commercial Lactobacillus paracasei strains, whereas two collection strains shared a third one. On the other hand, mitomycin C-inducible prophages were detected only on about a half of the strains isolated from dairy products, which had (with only one exception) from moderate to high correlation coefficients according to RAPD-PCR fingerprinting. After induction, supernatants were filtered and tested against nine Lactobacillus strains of the set sensitive to previously assayed virulent phages, allowing isolation of two new virulent phages: ф iLp1308 and ф iLp84. Both phages were able to lyse all but one strains sensitive to previously assayed phage MLC-A.     

In vitro assessment of the gastrointestinal transit tolerance of taxonomic reference strains from human origin and probiotic product isolates of Bifidobacterium

Next to health promoting effects, the functional aspect of probiotic strains also involves their capacity to reach the colon as viable metabolically active cells. The present study aimed to assess the potential of 24 probiotic product isolates and 42 human reference strains of Bifidobacterium to survive gastrointestinal transit under in vitro conditions. The survival capacity of exponential and stationary phase cultures upon exposure to gastric and small intestinal juices was determined using a recently developed microplate-based assay in combination with the LIVE/DEAD BacLight Bacterial Viability kit. All 66 strains tested displayed a considerable loss in viability during exposure to an acidic pepsin containing solution (pH 2.0). Among the 10 taxa tested, cultures of B. animalis ssp. lactis appeared to be most capable to survive gastric transit. Although to a lesser extent, the presence of bile salts also affected the viability of most of the strains tested. Except for 3 strains, all 66 strains showed bile salt hydrolase activity using an agar-based assay. In contrast, the bifidobacterial strains used in this study appeared to possess a natural ability to survive the presence of pancreatin (pH 8.0). Although the effect was not significant, a slightly enhanced tolerance to gastrointestinal transit was observed when cells were in the stationary phase, especially when exposed to acid, compared with cells being in the exponential phase. Survival in the gastrointestinal tract appeared to be largely strain-dependent and hence implies that different strains will likely display a different behavior in functionality. The assay used in this study allows an initial assessment of strains for use as probiotic cultures prior to selecting potential candidate strains for further investigation in vivo.     

Potential probiotic Lactobacillus strains from fermented sausages: Further investigations on their probiotic properties

A rational selection of probiotic microorganisms is an important challenge and requires the definition of fundamental information about the physiology and genetics of candidate strains. In this study, selected Lactobacillus (Lact.) strains already characterized in a previous study for their capability to resist low pH and to grow in conditions simulating the intestinal environment, were further investigated to explore their probiotic properties, such as the adhesion capability to intestinal human Caco-2 cell lines and their growth behaviour in the presence of various prebiotic carbohydrates. At first 25 Lactobacillus strains were characterized by pulsed field gel electrophoresis using the endonuclease NotI. Among them, 13 strains belonging to the Lact. plantarum-group were identified at species level by a multiplex PCR assay. Subsequently 11 Lactobacillus strains showing different PFGE restriction pattern and the best acid- and bile-resistances, were chosen to investigate their in vitro adhesion capability to human intestinal epithelial cells and their fermentation properties of five prebiotic substances (FOS, Inulin, IMO, GOS and lactulose) at a concentration of 2%. The 11 strains analysed in this study possessed good adhesion capability to Caco-2 cell layers and, in particular, the eight strains belonging to the Lact. plantarum-group showed the higher final number of viable adhering cells. Moreover a species-related fermentative behaviour was pointed out and the strain Lact. paracasei EL7 was the only one able to grow in the presence of all prebiotics tested. In conclusion the strains of Lactobacillus studied in this research could be further investigated to assess possible in vivo human health benefits.     

In vitro evaluation of gastrointestinal survival of Lactobacillus amylovorus DSM 16698 alone and combined with galactooligosaccharides, milk and/or Bifidobacterium animalis subsp. lactis Bb-12

Probiotic properties of Lactobacillus amylovorus DSM 16698 were previously demonstrated in piglets. Here, its potential as a human probiotic was studied in vitro, using the TIM-1 system, which is fully validated to simulate the human upper gastrointestinal tract. To evaluate the effect of the food matrix composition on the survival of L. amylovorus DSM 16698 in TIM-1, the microorganism was inoculated alone or with prebiotic galactooligosaccharides (GOS), partially skimmed milk (PSM) and/or commercial probiotic Bifidobacterium animalis subsp. lactis Bb-12 (Bb-12). Samples were collected from TIM-1 for six hours, at one-hour intervals and L. amylovorus populations were enumerated on MRS agar plates with confirmation of identity of selected isolates by randomly amplified polymorphic DNA (RAPD) fingerprinting. The cumulative survival for L. amylovorus alone (control) was 30% at the end of the experiment (t = 6 h). Co-administration of L. amylovorus with GOS, PSM and/or Bb-12 increased its survival in comparison with the control significantly from the 4th hour after ingestion onwards (P < 0.05). Furthermore, by the use of High Performance Anion Exchange Chromatography, both L. amylovorus and Bb-12 were observed to promptly degrade GOS compounds in samples collected from TIM-1, as assessed at t = 2 h. Hence, food matrix composition interfered with survival and growth of L. amylovorus during passage through TIM-1, providing leads towards optimization of probiotic properties in vivo.     

Survival of Lactobacillus rhamnosus strains in the upper gastrointestinal tract

In the present study six probiotic Lactobacillus rhamnosus strains were investigated for their ability to survive in the human upper gastrointestinal tract through a dynamic gastric model of digestion. MRS broth was used as delivery vehicle and survival was investigated during in vitro gastric and gastric plus duodenal digestion. Results highlighted that all tested strains showed good survival rate during both gastric and duodenal digestion. In particular, three strains exhibited a great survival showing a recovery percentage in the range between 117 and 276%. In agreement with survival data, high lactic acid production was detected for all strains, confirming their metabolic activity during digestion.     

Short communication: Survival of the characteristic microbiota in probiotic fermented camel,cow, goat,and sheep milks during refrigerated storage

The objective of this study was to monitor the viability during storage of Lactobacillus acidophilus LA-5 (A), Bifidobacterium animalis ssp. lactis BB-12 (B), and Streptococcus thermophilus CHCC 742/2130 (T) in probiotic cultured dairy foods made from pasteurized camel, cow, goat, and sheep milks fermented by an ABT-type culture. The products manufactured were stored at 4°C for 42 d. Microbiological analyses were performed at weekly intervals. Streptococcus thermophilus CHCC 742/2130 was the most numerous culture component in all 4 products both at the beginning and at the end of storage. The viable counts of streptococci showed no significant decline in fermented camel milk throughout the entire storage period. The initial numbers of Lb. acidophilus LA-5 were over 2 orders of magnitude lower than those of Strep. thermophilus CHCC 742/2130. With the progress of time, a slow and constant decrease was observed in lactobacilli counts; however, the final viability percentages of this organism did not differ significantly in the probiotic fermented milks tested. The cultured dairy foods made from cow, sheep, and goat milks had comparable B. animalis ssp. lactis BB-12 counts on d 0, exceeding by approximately 0.5 log₁₀ cycle those in the camel milk-based product. No significant losses occurred in viability of bifidobacteria in fermented camel, cow, and sheep milks during 6 wk of refrigerated storage. In conclusion, all 4 varieties of milk proved to be suitable raw materials for the manufacture of ABT-type fermented dairy products that were microbiologically safe and beneficial for human consumption. It was suggested that milk from small ruminants be increasingly used to produce probiotic fermented dairy foods. The development of camel milk-based probiotic cultured milks appears to be even more promising because new markets could thus be conquered. It must be emphasized, however, that further microbiological and sensory studies, technology development activities, and market research are needed before such food products can be successfully commercialized.     

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.     

Influence of adjunct use and cheese microenvironment on nonstarter bacteria in reduced-fat cheddar-type cheese

This study investigated population dynamics of starter, adjunct, and nonstarter lactic acid bacteria (NSLAB) in reduced-fat Cheddar and Colby cheese made with or without a Lactobacillus casei adjunct. Duplicate vats of cheese were manufactured and ripened at 7 degrees C. Bacterial populations were monitored periodically by plate counts and by DNA fingerprinting of cheese isolates with the random amplified polymorphic DNA technique. Isolates that displayed a unique DNA fingerprint were identified to the species level by partial nucleotide sequence analysis of the 16S rRNA gene. Nonstarter biota in both cheese types changed over time, but populations in the Colby cheese showed a greater degree of species heterogeneity. The addition of the L. casei adjunct to cheese milk at 10(4) cfu/ml did not completely suppress "wild" NSLAB populations, but it did appear to reduce nonstarter species and strain diversity in Colby and young Cheddar cheese. Nonetheless, nonstarter populations in all 6-mo-old cheeses were dominated by wild L. casei. Interestingly, the dominant strains of L. casei in each 6-mo-old cheese appeared to be affected more by adjunct treatment and not cheese variety.     

Tropical fruit pulps decreased probiotic survival to in vitro gastrointestinal stress in synbiotic soy yoghurt with okara during storage

The effect of mango and guava pulps on Lactobacillus acidophilus La-5 and Bifidobacterium animalis Bb-12 viability in a soy yoghurt (SY) and on probiotic survival under simulated gastrointestinal conditions were investigated throughout 28 days of storage at 4 °C. The impact of fruit pulps on SY sensory acceptability was also assessed. Three formulations were produced from soymilk fermented with ABT-4 culture (La-5, Bb-12, and Streptococcus thermophilus) and supplemented with inulin and okara: SYC (control), SYM (with mango pulp), and SYG (with guava pulp). All formulations showed probiotic viabilities ranging from 8 to 9 log cfu/g, and fruit pulps did not affect the probiotic viabilities. However, the fruit pulps decreased probiotic survival significantly to simulated gastrointestinal stress. Acceptability was higher for SYM and this difference was significant at 21 days. Therefore, the improved acceptability of SY through the addition of fruit pulps might lead to a reduction in probiotic functionality.     

Viability of Lactobacillus acidophilus La-5 added solely or in co-culture with a yoghurt starter culture and implications on physico-chemical and related properties of Minas fresh cheese during storage

The effect of a probiotic culture of Lactobacillus acidophilus (La-5), added solely or in co-culture with a starter culture of Streptococcus thermophilus, on texture, proteolysis and related properties of Minas fresh cheese during storage at 5 °C was investigated. Three cheese-making trials were prepared and produced with no addition of cultures (T1 - control), supplemented with La-5 (T2), and with La-5 + S. thermophilus (T3). Viable counts of La-5 remained above 6.00 log cfu g⁻¹ during the whole storage for T2, reaching 7.00 log cfu g⁻¹ on the 14th day. For T3, the counts of La-5 remained above 6.00 log cfu g⁻¹ after 7 days of storage. Due to the presence of S. thermophilus, T3 presented the highest proteolytic index increase and titratable acidity values. Nevertheless, these results and S. thermophilus addition had no influence on viability of La-5 which presented satisfactory populations for a probiotic food. Moreover, the use of a yoghurt culture for the production of Minas fresh cheese T3 supplemented with La-5 resulted in a good quality product, with a small rate of post-acidification, indicating that traditional yoghurt culture could be employed in co-culture with La-5 to improve the quality of this cheese.     

Effect of chestnut extract and chestnut fiber on viability of potential probiotic Lactobacillus strains under gastrointestinal tract conditions

The main challenge to probiotics, during their passage through the gastrointestinal tract, are the acidic gastric secretions of the stomach, and the bile salts released into the duodenum. The survival of the strains, in this phase, is strongly influenced by the food used for their delivery.     

益生菌发酵乳辅助调节机体健康的研究进展

益生菌发酵乳是益生菌的重要载体,可通过改善宿主肠道微生物菌群的平衡,促进有益成分代谢增强发酵乳的营养健康属性。文章阐述了益生菌发酵乳在改善肠道功能、调节机体免疫、辅助治疗代谢性疾病、改善神经系统疾病等方面的辅助功效,并对益生菌发酵乳的发展方向进行了展望。     

Safety and intestinal microbiota modulation by the exopolysaccharide-producing strains Bifidobacterium animalis IPLA R1 and Bifidobacterium longum IPLA E44 orally administered to Wistar rats

Bifidobacterium animalis subsp. lactis IPLA R1 and Bifidobacterium longum IPLA E44 strains were tested for their safety and ability to modulate the intestinal microbiota in vivo. Chemically simulated gastrointestinal digestion showed considerably lower survival of E44 than R1 strain, the first microorganism also being more sensitive to refrigerated storage in 10% skimmed milk at 4 °C. Harmful glycosidic activities were absent, or at low levels, in the strains R1 and E44. Both strains were sensitive to most antibiotics and resistant to aminoglycosides, a common feature in bifidobacteria. Similar to several other bifidobacteria strains, B. animalis subsp. lactis IPLA R1 displayed a moderate resistance against tetracycline which correlated with the presence of tet(W) gene in its genome. The general parameters indicating well-being status, as well as translocation to different organs and histological examination of the gut tissues, revealed no changes induced by the administration of bifidobacteria to rats. Twelve-week-old male Wistar rats were distributed into three groups, eight rats in each. Two groups were administered daily over 10⁸ cfu of the corresponding strain suspended in 10% skimmed milk for 24 days, whereas rats in the placebo group received skimmed milk without microorganisms added. The microbiota and short chain fatty acids (SCFA) were monitored in faeces at different time points during treatment and in caecum content at the end of the assay. Quantitative PCR (qPCR) showed that faecal and caecal Bifidobacterium levels were higher in bifidobacteria-fed rats than in the placebo rats at the end of the intervention, whereas total anaerobic plate counts did not show significant differences. Quantification of B. animalis and B. longum by qPCR showed that, independent of the microorganism administered, treatment with bifidobacteria resulted in higher levels of B. animalis in the caecum. PCR-DGGE analysis of microbial populations revealed a higher diversity of bands in caecum content of rats fed B. animalis IPLA R1 than in the placebo group and rats fed B. longum IPLA E44. Remarkably, although no variations in the proportion of acetate, propionate and butyrate were found, at the end of the assay the total SCFA concentration in the faeces of rats fed bifidobacteria was significantly higher and those in caecum content significantly lower, than that of the placebo group. This suggests a displacement of the SCFA production to parts of the colon beyond the caecum in rats receiving bifidobacteria. Therefore, the oral administration of B. animalis IPLA R1 and B. longum E44 can be considered safe, these microorganisms having the ability to modulate the intestinal microbiota of rats by influencing SCFA and the bifidobacterial population levels.     

Selective and differential enumerations of Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus casei and Bifidobacterium spp. in yoghurt--a review

Yoghurt is increasingly being used as a carrier of probiotic bacteria for their potential health benefits. To meet with a recommended level of ≥ 10⁶ viable cells/g of a product, assessment of viability of probiotic bacteria in market preparations is crucial. This requires a working method for selective enumeration of these probiotic bacteria and lactic acid bacteria in yoghurt such as Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, Lb. acidophilus, Lb. casei and Bifidobacterium. This chapter presents an overview of media that could be used for differential and selective enumerations of yoghurt bacteria. De Man Rogosa Sharpe agar containing fructose (MRSF), MRS agar pH 5.2 (MRS 5.2), reinforced clostridial prussian blue agar at pH 5.0 (RCPB 5.0) or reinforced clostridial agar at pH 5.3 (RCA 5.3) are suitable for enumeration of Lb. delbrueckii subsp. bulgaricus when the incubation is carried out at 45 °C for 72 h. S. thermophilus (ST) agar and M17 are recommended for selective enumeration of S. thermophilus. Selective enumeration of Lb. acidophilus in mixed culture could be made in Rogosa agar added with 5-bromo-4-chloro-3-indolyl-β-d-glucopyranoside (X-Glu) or MRS containing maltose (MRSM) and incubation in a 20% CO₂ atmosphere. Lb. casei could be selectively enumerated on specially formulated Lb. casei (LC) agar from products containing yoghurt starter bacteria (S. thermophilus and Lb. delbrueckii subsp. bulgaricus), Lb. acidophilus, Bifidobacterium spp. and Lb. casei. Bifidobacterium could be enumerated on MRS agar supplemented with nalidixic acid, paromomycin, neomycin sulphate and lithium chloride (MRS-NPNL) under anaerobic incubation at 37 °C for 72 h.     

Antioxidant activity of Lactobacillus plantarum strains isolated from traditional Chinese fermented foods

Eleven Lactobacillus plantarum strains isolated from traditional Chinese fermented foods were investigated for their in vitro scavenging activity against hydroxyl and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radicals, and their resistance to hydrogen peroxide. L. plantarum C88 at a dose of 10(10) CFU/ml showed the highest hydroxyl radical and DPPH scavenging activities, with inhibition rates of 44.31% and 53.05%, respectively. Resistance of intact cells to hydrogen peroxide was also found in all strains. L. plantarum C88 was the most resistant strain against hydrogen peroxide. When L. plantarum C88 was administered to senescent mice suffering oxidative stress induced by d-galactose, the serum superoxide dismutase activity, the glutathione peroxidase activity and the total antioxidant capacity in liver increased significantly, while the level of malondialdehyde in liver decreased significantly. L. plantarum C88 isolated from traditional Chinese fermented dairy tofu could be considered as a potential antioxidant to be applied in functional foods.     

Evaluation of culture media for selective enumeration of probiotic strains of lactobacilli and bifidobacteria in combination with yoghurt or cheese starters

A series of culture media were evaluated for selective enumeration of 10 commercial probiotic cultures. The media M17 and MRS 5.2 were most suitable to enumerate the yoghurt starters Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus, respectively. For the enumeration of probiotic Lb. acidophilus cultures, the MRS-clindamycin medium was found to be most optimal. Selective recovery results of the tested Bifidobacterium sp. were not uniform but indicated strain-to-strain variations depending on whether NPLN or MRS-LP were used. For the enumeration of probiotic cultures of Lb. rhamnosus and Lb. paracasei, LC medium (for yoghurt products) and MRS-AC medium (for cheese products) are recommended. In conclusion, our data indicate that the choice of culture medium and methodology for selective enumeration of commercial probiotic strains in combination with starters depends strongly on the product matrix, the target group and the taxonomic diversity of the bacterial background flora in the product.     

Survival and sensory acceptability of probiotic microorganisms in a nonfermented frozen vegetarian dessert

Probiotic microorganisms were incorporated into a nonfermented, vegetarian frozen soy dessert at initial populations greater than 10⁶ cfu/g. The product was assessed for the survival of probiotic microorganisms and sensory acceptability. Lactobacillus acidophilus MJLA1, L. rhamnosus 100-C, L. paracasei ssp. paracasei 01, Bifidobacterium lactis BBDB2, B. lactis BB-12 all survived the 6 month storage trial at populations of 10⁷ cfu/g or greater. Saccharomyces boulardii 74012 did not retain sufficient viability, decreasing below the desirable level of 10⁶ cfu/g. To detect sensory differences, product containing L. acidophilus MJLA1, S. boulardii 74012 and an uninoculated control were stored for 0, 4 and 7 months and compared using triangle tests. Product inoculated with L. acidophilus MJLA1 could not be distinguished from the control sample. Product with S. boulardii 74012 differed from the control and L. acidophilus MJLA1 and developed undesirable flavours during storage. The frozen soy dessert was a suitable food for the delivery of bacterial probiotic strains with excellent viability and acceptable sensory characteristics.     

Galactooligosaccharides derived from lactose and lactulose: influence of structure on Lactobacillus, Streptococcus and Bifidobacterium growth

The effect of structure on the fermentative properties of potential prebiotic trisaccharides derived from lactulose like 6′-galactosyl-lactulose (β-d-galactopyranosyl-(1 → 6)-β-d-galactopyranosyl-(1 → 4)-β-d-fructopyranose), 4′-galactosyl-lactulose (β-d-galactopyranosyl-(1 → 4)-β-d-galactopyranosyl-(1 → 4)-β-d-fructopyranose), and 1-galactosyl-lactulose (β-d-galactopyranosyl-(1 → 4)-β-d-fructopyranosyl-(1 → 1)-β-d-galactopyranose); and from lactose like 4′-galactosyl-lactose (β-d-galactopyranosyl-(1 → 4)-β-d-galactopyranosyl-(1 → 4)-β-d-glucopyranose) and 6′-galactosyl-lactose (β-d-galactopyranosyl-(1 → 6)-β-d-galactopyranosyl-(1 → 4)-β-d-glucopyranose), has been assessed in vitro. Fermentations with twelve pure strains of Lactobacillus, Streptococcus and Bifidobacterium were carried out using the purified trisaccharides as the sole carbon source, and bacteria growth was evaluated at 600 nm by means of a microplate reader during 48 h. Maximum growth rates (μ_max) and lag phase were calculated. In general, all the strains tested were able to utilize lactulose and pure trisaccharides derived from lactulose and lactose when they were used as sole carbon source. Nonetheless, glycosidic linkage and/or the monosaccharide composition of the trisaccharides affected the individual strains lag phase, cell densities and growth rates. A general preference towards β-galactosyl residues β(1-6) and β(1-1) linked over those β(1-4) linked was observed, and some strains showed higher cell densities and speed of growth on 6′-galactosyl-lactulose than on 6′-galactosyl-lactose. This is the first study of the effect of lactulose-derived oligosaccharides on pure culture growth which shows that transglycosylation of lactulose allows for obtaining galactooligosaccharides with new glycosidic structures and would open new routes to the synthesis of compounds with potential prebiotic effects.     

Volatile compounds produced by the probiotic strain Lactobacillus plantarum NCIMB 8826 in cereal-based substrates

The production of volatile compounds by the probiotic strain, Lactobacillus plantarum NCIMB 8826, in cereal-based media (oat, wheat, barley and malt) was investigated. Sixty compounds, including fatty acids and their esters, amides, alcohols, aldehydes, aromatic hydrocarbons, furans, ketones, peroxides and pyrans, were identified. L. plantarum significantly changed the aroma profile of the four cereal broths, and each substrate showed a specific volatiles profile. Oat and barley media were the substrates more influenced by the fermentation process. The most abundant volatiles detected in oat, wheat, barley and malt were oleic acid, linoleic acid, acetic acid, and 5-hydroxymethylfurfural, respectively. Analysis of these products confirmed the heterofermentative pathway of L. plantarum. Maillard compounds were not detected during sterilisation and fermentation. This study is the first to report the volatile composition of probiotic drinks produce with non-supplemented cereal-based media and the results obtained could contribute to the development of new non-dairy probiotic formulations.     

A comprehensive approach to determine the probiotic potential of human-derived Lactobacillus for industrial use

Specific strains should only be regarded as probiotics if they fulfill certain safety, technological and functional criteria. The aim of this work was to study, from a comprehensive point of view (in vitro and in vivo tests), three Lactobacillus strains (Lactobacillus paracasei JP1, Lactobacillus rhamnosus 64 and Lactobacillus gasseri 37) isolated from feces of local newborns, determining some parameters of technological, biological and functional relevance. All strains were able to adequately grow in different economic culture media (cheese whey, buttermilk and milk), which were also suitable as cryoprotectants. As selective media, LP-MRS was more effective than B-MRS for the enumeration of all strains. The strains were resistant to different technological (frozen storage, high salt content) and biological (simulated gastrointestinal digestion after refrigerated storage in acidified milk, bile exposure) challenges. L. rhamnosus 64 and L. gasseri 37, in particular, were sensible to chloramphenicol, erythromycin, streptomycin, tetracycline and vancomycin, increased the phagocytic activity of peritoneal macrophage and induced the proliferation of IgA producing cells in small intestine when administered to mice. Even when clinical trails are still needed, both strains fulfilled the main criteria proposed by FAO/WHO to consider them as potential probiotics for the formulation of new foods.