Survival of lactic acid bacteria in a dynamic model of the stomach and small intestine: validation and the effects of bile

Selection, characterisation and evaluation of potential probiotic Lactobacillus spp. isolated from poultry droppings

Aim of the present study was to characterise and evaluate probiotic potential of lactobacilli isolated from indigenous poultry. Lactobacilli were isolated from poultry droppings and identified by genus specific polymerase chain reaction and 16S rRNA gene sequencing. Isolates were characterised in vitro by their ability to tolerate low pH and bile salts, phytase activity, antimicrobial activity, antibiotic susceptibility profile, and autoaggregation and coaggregation with poultry gut pathogens. In vivo evaluation of selected isolates was done by their effect on the body weight gain and immune response of broiler chicks. Total of 90, one-day old chicks, were randomly divided in 9 groups and given selected lactobacilli alone and in combinations (10⁸ cfu/bird, daily) from day 7 to day 35. Body weight gain and humoral immune response to New Castle Disease Virus (NDV) vaccine were determined weekly. Three lactobacilli isolates (SMP52, SMP64 and SMP70) were selected as potentially probiotic bacteria on the basis of in vitro characterisation and identified as Lactobacillus crispatus, Lactobacillus casei and L. crispatus, respectively. Chicks supplemented with 'SMP52', 'SMP64', 'SMP70' and 'SMP64+SMP70' and a commercial probiotic product (Protexin) showed significantly higher mean weight gain per bird (1,584±35.2, 1,629±30.6, 1,668±34.7, 1,619±29.5 and 1,576±31.7 g/bird, respectively) as compared to negative control group (1,394±26.7 g/bird), on day 35. SMP 70 also showed significantly higher geometric mean titre against NDV vaccine at day 21 as compared to negative control. It is concluded that L. crispatus SMP52, L. casei SMP64 and L. crispatus SMP70 are potential probiotic candidates which alone or in different combinations may increase body weight of broilers.

Effects of milk components and food additives on survival of three bifidobacteria strains in fermented milk under simulated gastrointestinal tract conditions

Background

In the dairy industry, probiotic strains of Bifidobacterium are introduced into the composition of traditional starter cultures intended for the production of fermented foods, or sometimes are the sole microflora responsible for the fermentation process. In order to be able to reach the intestines alive and fulfil their beneficial role, probiotic strains must be able to withstand the acidity of the gastric juices and bile present in the duodenum.

Objective

The paper reports effects of selected fermented milk components on the viability of three strains of bifidobacteria in fermented milk during subsequent incubation under conditions representing model digestive juices.

Design

The viability of the bifidobacterial cells was examined after a 3-h incubation of fermented milk under simulated gastric juice conditions and then after 5-h incubation under simulated duodenum juice conditions. The Bifidobacterium strains tested differed in their sensitivity to the simulated conditions of the gastrointestinal juices.

Results

Bifidobacterial cell viability in simulated intestinal juices was dependent on the strain used in our experiments, and product components acted protectively towards bifidobacterial cells and its dose.

Conclusions

Bifidobacterial cells introduced into the human gastrointestinal tract as food ingredients have a good chance of survival during intestinal transit and to reach the large intestine thanks to the protective properties of the food components and depending on the strain and composition of the food.

In vitro probiotic characterization ofLactobacillusstrains from fermented radish and their anti-adherence activity against enteric pathogens

In this study, we evaluated the probiotic properties of Lactobacillus plantarum, Lactobacillus pentosus, and Lactobacillus fermentum strains isolated from fermented radish. All the strains survived the simulated oro-gastrointestinal transit condition and showed significantly higher adherence to Caco-2 cells compared with the probiotic strain Lactobacillus rhamnosus GG. The strains showed broad-spectrum antimicrobial activity, autoaggregation, and coaggregation capacity with pathogens. Furthermore, the Lactobacillus strains inhibited the adherence of Yersinia enterocolitica subsp. enterocolitica, Shigella boydii, and Salmonella choleraesuis to the Caco-2 cell line. The strains possessed bile salt hydrolase activity and their cholesterol-lowering activity in vitro was above 50% in the presence of bile. Strains of L. plantarum and L. pentosus possessed the plantaricin-encoding plnEF gene. In addition, the Lactobacillus strains maintained about 80% cell viability after freeze–drying in the presence of a combination of 5% skim milk and 5% maltodextrin as cryoprotectant, and 70% recovery of cell viability was observed in the absence of any cryoprotectant.

Preliminary probiotic and technological characterization of Pediococcus pentosaceus strain KID7 and in vivo assessment of its cholesterol-lowering activity

The study was aimed to characterize the probiotic properties of a Pediococcus pentosaceus strain, KID7, by in vitro and in vivo studies. The strain possessed tolerance to oro-gastrointestinal transit, adherence to the Caco-2 cell line, and antimicrobial activity. KID7 exhibited bile salt hydrolase activity and cholesterol-lowering activity, in vitro. In vivo cholesterol-lowering activity of KID7 was studied using atherogenic diet-fed hypercholesterolemic mice. The experimental animals (C57BL/6J mice) were divided into 4 groups viz., normal diet-fed group (NCD), atherogenic diet-fed group (HCD), atherogenic diet- and KID7-fed group (HCD-KID7), and atherogenic diet- and Lactobacillus acidophilus ATCC 43121-fed group (HCD-L.ac) as positive control. Serum total cholesterol (T-CHO) level was significantly decreased by 19.8% in the HCD-KID7 group (P < 0.05), but not in the HCD-L.ac group compared with the HCD group. LDL cholesterol levels in both HCD-KID7 and HCD-L.ac groups were decreased by 35.5 and 38.7%, respectively, compared with HCD group (both, P < 0.05). Glutamyl pyruvic transaminase (GPT) level was significantly lower in the HCD-KID7 and HCD-L.ac groups compared to HCD group and was equivalent to that of the NCD group. Liver T-CHO levels in the HCD-KID7 group were reduced significantly compared with the HCD group (P < 0.05) but not in the HCD-L.ac group. Analysis of expression of genes associated with lipid metabolism in liver showed that low-density lipoprotein receptor (LDLR), cholesterol-7α-hydroxylase (CYP7A1) and apolipoprotein E (APOE) mRNA expression was significantly increase in the HCD-KID7 group compared to the HCD group. Furthermore, KID7 exhibited desired viability under freeze-drying and subsequent storage conditions with a combination of skim milk and galactomannan. P. pentosaceus KID7 could be a potential probiotic strain, which can be used to develop cholesterol-lowering functional food after appropriate human clinical trials.

Characterisation and preliminary lipid-lowering evaluation of Lactobacillus isolated from a traditional Serbian dairy product

We investigated the potential probiotic properties of indigenous lactic acid bacteria (LAB) isolated from Serbian homemade cheese. Seventeen LAB strains were isolated and characterised using standard protocols. One of the strains showed several probiotic properties: survival at low pH and in bile salts solution, antimicrobial activity, susceptibility to antibiotics and adhesion to hexodecane. DNA analysis identified the isolate as Lactobacillus casei, hereafter named L. casei 5s. The lipid lowering effect of L. casei 5s was evaluated in vivo using a hyperlipidemic rat model. Orally administered L. casei 5s significantly decreased the elevated total serum cholesterol and triglycerides, and attenuated macro vesicular steatosis in the liver. Moreover, L. casei 5s improved the intestinal microbial balance in favour of lactobacilli, while decreasing the number of Escherichia coli cells. The bacteria were re-isolated and identified from the surface of the intestinal mucosa and from the faecal samples of treated animals, indicating adhesiveness and colonisation ability. The results of an acute oral toxicity study in mice and the absence of translocation to other organs demonstrated the safety of the strain. In conclusion, L. casei 5s demonstrated promising probiotic potential and might be a good candidate for more detailed investigations.

Effect of intestinal colonisation by two Lactobacillus strains on the immune response of gnotobiotic mice

The effect of intestinal colonisation on the immune system was investigated in germ-free mice monoassociated with Lactobacillus strains isolated from calf faeces. Single doses of Lactobacillus acidophilus L36 or Lactobacillus salivarius L38 were administered to germ-free mice by intragastric gavage. Ten days later, the mice were euthanised. Gene expression levels of interleukin 5 (IL-5), IL-6, IL-10, IL-12b, IL-17a, gamma interferon (IFN-γ), transforming growth factor beta 1 (TGF-β1), and tumour necrosis factor alpha (TNF-α) were quantified in segments of the small and large intestines by real time quantitative polymerase chain reaction. All the mice were colonised rapidly after Lactobacillus administration with intestinal counts ranging from 6.53 to 8.26 log cfu/g. L. acidophilus L36 administration increased the expression of cytokines involved with the Th2 (IL-5, IL-6 and TGF-β1) and Th17 (IL-17a, TNF-α and IL-6) inflammatory response, whereas L. salivarius L38 appeared to stimulate a pattern of less diversified cytokines in the intestine. Intragastric gavage of L. acidophilus L36 and L. salivarius L38 induced similar levels of colonisation in the digestive tracts of germ-free mice but stimulated different immune responses in the intestinal mucosa. The different immunomodulation patterns might facilitate the potential use of these lactobacilli as probiotics to treat distinct pathological conditions, for example protection against Citrobacter rodentium infection by stimulating IL-17 production.

Assessment of probiotic potential and anticancer activity of newly isolated vaginal bacterium Lactobacillus plantarum 5BL

Numerous bacteria in and on its external parts protect the human body from harmful threats. This study aimed to investigate the potential beneficial effects of the vaginal ecosystem microbiota. A type of bacteria was isolated from vaginal secretions of adolescent and young adult women, cultured on an appropriate specific culture medium, and then molecularly identified through 16S rDNA gene sequencing. Results of 16S rDNA sequencing revealed that the isolate belongs to the Lactobacillus plantarum species. The isolated strain exhibited probiotic properties such as low pH and high bile salt concentration tolerance, antibiotic susceptibility and antimicrobial activity against some pathogenic bacteria. The anticancer effects of the strain on human cancer cell lines (cervical, HeLa; gastric, AGS; colon, HT-29; breast, MCF-7) and on a human normal cell line (human umbilical vein endothelial cells [HUVEC]) were investigated. Toxic side effects were assessed by studying apoptosis in the treated cells. The strain exhibited desirable probiotic properties and remarkable anticancer activity against the tested human cancer cell lines (P ≤ 0.05) with no significant cytotoxic effects on HUVEC normal cells (P ≤ 0.05). Overall, the isolated strain showed favorable potential as a bioactive therapeutic agent. Therefore, this strain should be subjected to the other required tests to prove its suitability for clinical therapeutic application.

Therapeutic effects of Lactobacillus casei Qian treatment in activated carbon-induced constipated mice

In the present study, the therapeutic effects of Lactobacillus casei Qian (LC-Qian), the key microorganism in Tibetan yak yoghurt, on activated carbon-induced constipation were determined in vivo. ICR mice were treated with LC-Qian for nine days by oral administration. The body weight, defecation status, gastrointestinal transit and defecation time of mice were assessed, and the serum levels of motilin (MTL), gastrin (Gas), endothelin (ET), somatostatin (SS), acetylcholinesterase (AChE), substance P (SP) and vasoactive intestinal peptide (VIP) were further evaluated. Bisacodyl was used as the positive control. The time until the first black stool defecation following carbon intake of the normal, control, 100 mg/kg bisacodyl-treated, Lactobacillus bulgaricus (LB)-treated, LC-Qian (L)-and LC-Qian (H)-treated mice was 93, 231, 121, 194, 172 and 157 min, respectively. Following treatment with LC-Qian, the gastrointestinal transit was increased to 52.4% [LC-Qian (L)] and 65.8% [LC-Qian (H)], while that in the group treated with the common lactic acid bacteria of LB was 40.3%. The MTL, Gas, ET, AChE, SP and VIP serum levels were significantly increased and levels of SS were reduced in mice following LC-Qian treatment compared with those in the control mice (P<0.05). Reverse transcription quantitative polymerase chain reaction indicated that LC-Qian raised the c-Kit, GDNF as well as SCF mRNA expression levels and reduced the TRPV1 and NOS expression levels in tissue of the small intestine in mice. These results suggested that lactic acid bacteria prevent constipation in mice, among which LC-Qian was the most effective.

Bioaccessible antioxidants in milk fermented by Bifidobacterium longum subsp. longum strains

Bifidobacterium longum subsp. longum is among the dominant species of the human gastrointestinal microbiota and could thus have potential as probiotics. New targets such as antioxidant properties have interest for beneficial effects on health. The objective of this study was to evaluate the bioaccessibility of antioxidants in milk fermented by selected B. longum subsp. longum strains during in vitro dynamic digestion. The antioxidant capacity of cell extracts from 38 strains, of which 32 belong to B. longum subsp. longum, was evaluated with the ORAC (oxygen radical absorbance capacity) method. On the basis of screening and gene sequence typing by multilocus locus sequence analysis (MLSA), five strains were chosen for fermenting reconstituted skim milk. Antioxidant capacity varied among the strains tested (P = 0.0009). Two strains of B. longum subsp. longum (CUETM 172 and 171) showed significantly higher ORAC values than the other bifidobacteria strains. However, there does not appear to be a relationship between gene sequence types and antioxidant capacity. The milk fermented by each of the five strains selected (CUETM 268, 172, 245, 247, or PRO 16-10) did not have higher initial ORAC values compared to the nonfermented milk samples. However, higher bioaccessibility of antioxidants in fermented milk (175–358%) was observed during digestion.

Discovering probiotic microorganisms: in vitro, in vivo, genetic and omics approaches

Over the past decades the food industry has been revolutionized toward the production of functional foods due to an increasing awareness of the consumers on the positive role of food in wellbeing and health. By definition probiotic foods must contain live microorganisms in adequate amounts so as to be beneficial for the consumer’s health. There are numerous probiotic foods marketed today and many probiotic strains are commercially available. However, the question that arises is how to determine the real probiotic potential of microorganisms. This is becoming increasingly important, as even a superficial search of the relevant literature reveals that the number of proclaimed probiotics is growing fast. While the vast majority of probiotic microorganisms are food-related or commensal bacteria that are often regarded as safe, probiotics from other sources are increasingly being reported raising possible regulatory and safety issues. Potential probiotics are selected after in vitro or in vivo assays by evaluating simple traits such as resistance to the acidic conditions of the stomach or bile resistance, or by assessing their impact on complicated host functions such as immune development, metabolic function or gut–brain interaction. While final human clinical trials are considered mandatory for communicating health benefits, rather few strains with positive studies have been able to convince legal authorities with these health claims. Consequently, concern has been raised about the validity of the workflows currently used to characterize probiotics. In this review we will present an overview of the most common assays employed in screening for probiotics, highlighting the potential strengths and limitations of these approaches. Furthermore, we will focus on how the advent of omics technologies has reshaped our understanding of the biology of probiotics, allowing the exploration of novel routes for screening and studying such microorganisms.

Role of the gut in modulating lipoprotein metabolism

The intestinal production of lipoproteins is one of the key processes by which the body prepares dietary lipid for dissemination to locations throughout the body where they are required. Paramount to this is the relationship between dietary lipid and the enterocytes that line the gut, along with the processes which prepare this lipid for efficient uptake by these cells. These include those which occur in the mouth and stomach along with those which occur within the intestinal lumen itself. Additionally, the interplay between digested lipid, dual avenues for lipid uptake by enterocytes (passive and lipid transporter proteins), a system of intercellular lipid resynthesis and transport, and a complex system of lipoprotein synthesis yield a system open to significant modulation. In this review, we will attempt to outline the processes of lipid digestion, lipoprotein synthesis and the exogenous and endogenous factors which exert their influence.

Effects of lactic acid bacteria on low-density lipoprotein susceptibility to oxidation and aortic fatty lesion formation in hyperlipidemic hamsters

We investigated the effects of Streptococcus thermophilus YIT 2001, a strain of lactic acid bacteria, on the susceptibility of low-density lipoprotein (LDL) to oxidation and the formation of aortic fatty lesions in hyperlipidemic hamsters. S. thermophilus YIT 2001 had the highest in vitro antioxidative activity against LDL oxidation among the 79 strains of lactic acid bacteria and bifidobacteria tested, which was about twice that of S. thermophilus YIT 2084. The lag time of LDL oxidation in the YIT 2001 feeding group was significantly longer than in controls, but was unchanged in the YIT 2084 group. After the feeding of YIT 2001, lag times were prolonged and areas of aortic fatty lesions were dose-dependently attenuated, although there were no effects on plasma lipid levels. These results suggest that YIT 2001 has the potential to prevent the formation of aortic fatty lesions by inhibiting LDL oxidation.

Lactococcus lactis ssp. lactis as Potential Functional Starter Culture

The aim of this study is to identify and characterise potential autochthonous functional starter cultures in homemade horsemeat sausage. The dominant microflora in the samples of horsemeat sausage were lactic acid bacteria (LAB), followed by micrococci. Among the LAB, Lactococcus lactis ssp. lactis and Lactobacillus plantarum were the dominant species, and since the first is not common in fermented sausages, we characterised it as a potential functional starter culture. Lactococcus lactis ssp. lactis produced a significant amount of lactic acid, displayed good growth capability at 12, 18 and 22 °C, growth in the presence of 5% NaCl, good viability after lyophilisation and in simulated gastric and small intestinal juice, antimicrobial activity against test pathogens, and good adhesive properties in vitro.

Effect of chitosan coating on a bacteria-based alginate microrobot

To develop an efficient bacteria-based microrobot, first, therapeutic bacteria should be encapsulated into microbeads using biodegradable and biocompatible materials; second, the releasing rate of the encapsulated bacteria for theragnostic function should be regulated; and finally, flagellated bacteria should be attached on the microbeads to ensure the motility of the microrobot. For the therapeutic bacteria encapsulation, an alginate can be a promising candidate as a biodegradable and biocompatible material. Owing to the non-regulated releasing rate of the encapsulated bacteria in alginate microbeads and the weak attachment of flagellated bacteria on the surface of alginate microbeads, however, the alginate microbeads cannot be used as effective cargo for a bacteria-based microrobot. In this paper, to enhance the stability of the bacteria encapsulation and the adhesion of flagellated bacteria in alginate microbeads, we performed a surface modification of alginate microbeads using chitosan coating. The bacteria-encapsulated alginate microbeads with 1% chitosan coating maintained their structural integrity up to 72 h, whereas the control alginate microbead group without chitosan coating showed severe degradations after 24 h. The chitosan coating in alginate microbeads shows the enhanced attachment of flagellated bacteria on the surface of alginate microbeads. The bacteria-actuated microrobot with the enhanced flagellated bacteria attachment could show approximately 4.2 times higher average velocities than the control bacteria-actuated microrobot without chitosan coating. Consequently, the surface modification using chitosan coating enhanced the structural stability and the motility of the bacteria-based alginate microrobots.

Preventive effect of Lactobacillus fermentum Lee on activated carbon-induced constipation in mice

The aim of this study was to investigate the effects of Lactobacillus fermentum Lee (LF-Lee) on activated carbon-induced constipation in ICR mice. ICR mice were orally administered lactic acid bacteria for nine days. Body weight, dietary and water intake, defecation status, gastrointestinal (GI) transit and defecation time, as well as levels of motilin (MTL), gastrin (Gas), endothelin (ET), somatostatin (SS), acetylcholinesterase (AChE), substance P (SP) and vasoactive intestinal peptide (VIP) in serum were measured to evaluate the preventive effects of LF-Lee on constipation. Bisacodyl, a laxative drug, was administered as a positive control. The time taken until the first defecation of a black stool for normal, control, bisacodyl- (100 mg/kg, oral administration), Lactobacillus bulgaricus (LB)-, LF-Lee low dose (L)- and LF-Lee high dose (H)-treated mice was 90, 218, 117, 180, 161 and 151 min, respectively. Following the consumption of LB, LF-Lee (L) or LF-Lee (H), or the oral administration of bisacodyl, the GI transit was reduced to 55.2, 65.8, 73.1 and 94.6%, respectively, of the transit in normal mice. The serum levels of MTL, Gas, ET, AChE, SP and VIP were significantly increased and those of SS were reduced in the mice treated with LF-Lee compared with those in the untreated control mice (P<0.05). These results demonstrate that lactic acid bacteria have preventive effects on constipation in mice and that LF-Lee has superior functional activity.

Probiotics against neoplastic transformation of gastric mucosa: Effects on cell proliferation and polyamine metabolism

Gastric cancer is still the second leading cause of cancer death worldwide, accounting for about 10% of newly diagnosed neoplasms. In the last decades, an emerging role has been attributed to the relations between the intestinal microbiota and the onset of both gastrointestinal and non-gastrointestinal neoplasms. Thus, exogenous microbial administration of peculiar bacterial strains (probiotics) has been suggested as having a profound influence on multiple processes associated with a change in cancer risk. The internationally accepted definition of probiotics is live microorganisms that, when administered in adequate amounts, confer a health benefit on the host. The possible effects on the gastrointestinal tract following probiotic administration have been investigated in vitro and in animal models, as well as in healthy volunteers and in patients suffering from different human gastrointestinal diseases. Although several evidences are available on the use of probiotics against the carcinogen Helicobacter pylori, little is still known about the potential cross-interactions among probiotics, the composition and quality of intestinal flora and the neoplastic transformation of gastric mucosa. In this connection, a significant role in cell proliferation is played by polyamines (putrescine, spermidine, and spermine). These small amines are required in both pre-neoplastic and neoplastic tissue to sustain the cell growth and the evidences here provided suggest that probiotics may act as antineoplastic agents in the stomach by affecting also the polyamine content and functions. This review will summarize data on the most widely recognized effects of probiotics against neoplastic transformation of gastric mucosa and in particular on their ability in modulating cell proliferation, paying attention to the polyamine metabolism.

Autism and nutrition: the role of the gut-brain axis

Autism spectrum disorder (ASD) is characterised by deficits in the ability to socialise, communicate and use imagination, and displays of stereotypical behaviour. It is widely accepted that ASD involves a disorder in brain development. However, the real causes of the neurodevelopmental disorders associated with ASD are not clear. In this respect, it has been found that a majority of children with ASD display gastrointestinal symptoms, and an increased intestinal permeability. Moreover, large differences in microbiotic composition between ASD patients and controls have been reported. Therefore, nutrition-related factors have been hypothesised to play a causal role in the aetiology of ASD and its symptoms. Through a review of the literature, it was found that abnormalities in carbohydrate digestion and absorption could explain some of the gastrointestinal problems observed in a subset of ASD patients, although their role in the neurological and behavioural problems remains uncertain. In addition, the relationship between an improved gut health and a reduction of symptoms in some patients was evaluated. Recent trials involving gluten-free diets, casein-free diets, and pre- and probiotic, and multivitamin supplementation show contradictive but promising results. It can be concluded that nutrition and other environmental influences might trigger an unstable base of genetic predisposition, which may lead to the development of autism, at least in a subset of ASD patients. Clear directions for further research to improve diagnosis and treatment for the different subsets of the disorder are provided.

In Vitro Study of Potentially Probiotic lactic Acid Bacteria Strains Isolated From Traditional Dairy Products

BACKGROUND

Probiotic microorganisms are selected based on their long history of use as well as their lack of side effects. Nowadays, the consumption of probiotic products is growing intensively in developing countries. Researchers who work in the food industry and research centers pay more attention to the identification of new probiotic bacteria with better performance characteristics as well as investigation of their performance because these findings can be very effective in promoting sale and consumption of these products.

OBJECTIVES

HENCE, THIS STUDY WAS PERFORMED FOLLOWING THESE OBJECTIVES: isolating indigenous lactic acid bacteria from traditional dairy products in Markazi Province, screening strains with probiotic characteristics, identifying strains and performing microbial collection of probiotic strains with indigenous potential.

MATERIALS AND METHODS

In this study, the samples were screened from traditional dairy products, such as fresh yogurt, curd, Tarhana and Ghareghoroot of Markazi Province villages. Samples were enriched in de Man, Rogosa and Sharpe (MRS) broth, and different strains were isolated and purified from this culture on MRS agar medium. Isolated strains were investigated by microscopic observations, considering the following factors: catalase capability, resistance to acid and bile, bile salt hydrolysis and antibiotic susceptibility pattern.

RESULTS

Nineteen Gram-positive and catalase-negative strains belonging to the Lactobacillus genus were isolated from the above-mentioned diary samples. Seven strains were resistant to acid and bile in which acid resistance was between 21.08% and 122.33% and bile resistance was between 94.08% and 152.93%, respectively. All isolated strains were susceptible to different antibiotics and a small percentage had the ability to hydrolyze Sodium Taurocholate.

CONCLUSIONS

There are many of different species of Lactobacillus probiotics in traditional dairy products of the Markazi province, based on the findings of this study. It is recommended for researchers to isolate these strains and investigate their probiotic characteristics in order to reproduce them for use in food production as well as for medical treatment.

Generation of food-grade recombinant Lactobacillus casei delivering Myxococcus xanthus prolyl endopeptidase

Prolyl endopeptidases (PEP) (EC 3.4.21.26), a family of serine proteases with the ability to hydrolyze the peptide bond on the carboxyl side of an internal proline residue, are able to degrade immunotoxic peptides responsible for celiac disease (CD), such as a 33-residue gluten peptide (33-mer). Oral administration of PEP has been suggested as a potential therapeutic approach for CD, although delivery of the enzyme to the small intestine requires intrinsic gastric stability or advanced formulation technologies. We have engineered two food-grade Lactobacillus casei strains to deliver PEP in an in vitro model of small intestine environment. One strain secretes PEP into the extracellular medium, whereas the other retains PEP in the intracellular environment. The strain that secretes PEP into the extracellular medium is the most effective to degrade the 33-mer and is resistant to simulated gastrointestinal stress. Our results suggest that in the future, after more studies and clinical trials, an engineered food-grade Lactobacillus strain may be useful as a vector for in situ production of PEP in the upper small intestine of CD patients.

Immunomodulating activity of exopolysaccharide-producing Leuconostoc mesenteroides strain NTM048 from green peas

AIMS

The present work was aimed to find novel probiotics to enhance the mucosal barrier function of humans. The effectiveness was evaluated in vitro and in vivo.

METHODS AND RESULTS

Stimulation of IgA production in mucosal surfaces is one of the most beneficial traits of lactic acid bacteria (LAB) for enhancing the barrier. Therefore, 173 LAB strains were evaluated for the ability to induce IgA production using murine Peyer's patch cells. Strain NTM048 isolated from green peas showed the highest activity and was identified as Leuconostoc mesenteroides subsp. mesenteroides. This strain was found to tolerate gastrointestinal digestion and produce large amounts of exopolysaccharides, which possess IgA-inducing activity. Dietary supplementation with NTM048 induced a significant increase in the faecal IgA content and plasma IgA levels of BALB/cA mice. A gene expression analysis of Peyer's patch cells revealed that the transforming growth factor-β and activation-induced cytidine deaminase genes were upregulated by NTM048 intake.

CONCLUSIONS

Strain NTM048 stimulates Peyer's patch cells to induce intestinal and systemic immune response, revealing the potential of NTM048 as a probiotic for enhancing the mucosal barrier function.

SIGNIFICANCE AND IMPACT OF THE STUDY

This report demonstrates a food-applicable Leuconostoc mesenteroides strain secreting exopolysaccharide that shows high IgA-inducing ability.

Bacteriocinogenic properties and in vitro probiotic potential of enterococci from Tunisian dairy products

The aim of this study was to isolate new bacteriocinogenic strains with putative probiotic potential from various Tunisian fermented milks. A total of 44 Gram-positive catalase-negative isolates were colony-purified and screened for antimicrobial activity. Of inhibitory isolates, four were identified as Enterococcus durans and one as Enterococcus faecalis using 16S rRNA gene sequence. The five strains were sensitive to penicillin G, all aminoglycosides tested, to the vancomycin, tetracycline, and chloramphenicol, and E. durans 42G and E. faecalis 61B were resistant to erythromycin. The antimicrobial substances were sensitive to proteolytic enzymes and had good biochemical stability. E. durans 61A showed a good resistance to gastric and small intestinal secretions, but were more sensitive to the duodenal conditions. Considering the safety and the stability under simulated gastrointestinal tract, it appears that the bacteriocinogenic strain E. durans 61A is a good candidate for its application as novel probiotic strain in the food industry.

Effect of the gastrointestinal environment on pH homeostasis of Lactobacillus plantarum and Lactobacillus brevis cells as measured by real-time fluorescence ratio-imaging microscopy

In the present work, an in vitro model of the gastrointestinal tract (GIT) was developed to obtain real-time observations of the pH homeostasis of single cells of probiotic Lactobacillus spp. strains as a measure of their physiological state. Changes in the intracellular pH (pHi) were determined using fluorescence ratio imaging microscopy (FRIM) for potential probiotic strains of Lactobacillus plantarum UFLA CH3 and Lactobacillus brevis UFLA FFC199. Heterogeneous populations were observed, with pHi values ranging from 6.5 to 7.5, 3.5 to 5.6 and 6.5 to 8.0 or higher during passage of saliva (pH 6.4), gastric (pH 3.5) and intestinal juices (pH 6.4), respectively. When nutrients were added to gastric juice, the isolate L. brevis significantly decreased its pH(i) closer to the extracellular pH (pH(ex)) than in gastric juice without nutrients. This was not the case for L. plantarum. This study is the first to produce an in vitro GIT model enabling real-time monitoring of pH homeostasis of single cells in response to the wide range of pH(ex) of the GIT. Furthermore, it was possible to observe the heterogeneous response of single cells. The technique can be used to determine the survival and physiological conditions of potential probiotics and other microorganisms during passage through the GIT.

Pediococcus acidilactici UL5 and Lactococcus lactis ATCC 11454 are able to survive and express their bacteriocin genes under simulated gastrointestinal conditions

AIMS

The aim of this work is to study the expression of stress genes and those involved in pediocin and nisin production in Pediococcus acidilactici UL5 and Lactococcus lactis ATCC11454 under simulated gastrointestinal (GI) physiological conditions.

METHODS AND RESULTS

The two strains were fed to a dynamic GI model (TIM-1). Samples were taken from different compartments and analysed for strain survival as well as for the expression of pediocin PA-1 operon, nisin A production gene and stress genes using RT-qPCR. Ileal-delivered efflux showed a survival rate of 17 and 0·0007% for Ped. acidilactici and La. lactis, respectively. Pediocin operon genes from stressed cells were generally expressed at least at the same level as for unstressed cells. However, pedA is up-regulated in the effluent at 120 and 180 min. Nisin A genes were always up-regulated with particularly in the stomach after 70 min compared with control.

CONCLUSIONS

Bacteriocin production of Ped. acidilactici UL5 and Lc. lactis ATCC 11454 are not affected by upper GI simulated conditions and thus could be considered as relevant probiotic candidates.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study demonstrates the capacity of lactic acid bacteria to survive and express their bacteriocins genes under simulated GI conditions.

Long-Term Use of Probiotic-Containing Yogurts Is a Safe Way to Prevent Helicobacter pylori: Based on a Mongolian Gerbil's Model

Background. The suppression of Helicobacter pylori (H. pylori) decreases H. pylori-related diseases. The probiotics have an inhibitory effect on H. pylori. Aim. We investigated the effects of long-term use of yogurt on H. pylori based on Mongolian gerbils' model. Materials and Methods. Yogurt (containing a supplement of Lactobacillus acidophilus, Bifidobacterium lactis, etc.) was used. Forty-six gerbils were divided into five groups. All groups were inoculated with H. pylori for 5 to 8 weeks. The yogurt was given as follows: Group (Gr.) A: from 1st to 4th week; Gr. B from 5th to 8th week; Gr. C: from 17th week to sacrifice; Gr. D: from 5th week to sacrifice. Gerbils were sacrificed on the 52nd week. Histology was evaluated according to the Sydney system. Results. The positive rates of H. pylori were 60% (Gr. A), 75% (Gr. B), 67% (Gr. C), 44% (Gr. D), and 100% (Gr. E). Gr. D showed lower inflammatory score. Only Gr. E (60%) had intestinal metaplasia. Gr. D showed higher IL-10 and lower TNF-α expression than Gr. E. Conclusion. Long-term intake of yogurt could decrease H. pylori infection. The long-term use of yogurt would be an alternative strategy to manage H. pylori infection.

Antiproliferative and proapoptotic effects of viable or heat-killed Lactobacillus paracasei IMPC2.1 and Lactobacillus rhamnosus GG in HGC-27 gastric and DLD-1 colon cell lines

Data from literature suggest the possible use of probiotics as chemopreventive agents against colon cancer, but few investigations are available on their effects on gastric cancer proliferation. In our previous study, a specific Lactobacillus, strain L. paracasei IMPC2.1, was demonstrated to colonize the human gut and positively affect fecal bacteria and biochemical parameters. The aims of the present study were to investigate the effects of L. paracasei IMPC2.1, comparing them with those of Lactobacillus rhamnosus GG (L.GG), either as viable or heat-killed cells, on cell proliferation and apoptosis in a gastric cancer (HGC-27) and a colorectal cancer cell line (DLD-1). Both the gastric and colon cancer cells were sensitive to the growth inhibition and apoptosis induction by both viable or heat-killed cells from L. paracasei IMPC2.1 and L.GG. These findings suggest the possibility for a food supplement, based on dead probiotics, including L. paracasei IMPC2.1 cells, which could represent an effective component of a functional food strategy for cancer growth inhibition, with potential for cancer prevention.

Influence of Bacillus subtilis C-3102 on microbiota in a dynamic in vitro model of the gastrointestinal tract simulating human conditions

Survival and germination rate of Bacillus subtilis C-3102 spores were investigated in a stomach and small intestine model (TIM-1), while the impact of C-3102 cells that had passed through TIM-1 on human colon microbiota was evaluated in a model of the large intestine (TIM-2). The survival of C-3102 spores in TIM-1 was 99%; 8% of the spores had germinated. Effluent of TIM-1 was subsequently introduced into TIM-2 and a micro-array platform was employed to assess changes in the microbiota composition. The effluent, which contained germinated C-3102 cells, increased some Bifidobacterium species and decreased some Clostridium groups. These changes were greater compared to those obtained by adding C-3102 spores directly to TIM-2. The present study suggests that oral doses of B. subtilis C-3102 spores have the potential to modulate the human colon microbiota. This effect may be caused by germination of the spores in the gastrointestinal tract.

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.

Biogenic amine production by the wine Lactobacillus brevis IOEB 9809 in systems that partially mimic the gastrointestinal tract stress

Background

Ingestion of fermented foods containing high levels of biogenic amines (BA) can be deleterious to human health. Less obvious is the threat posed by BA producing organisms contained within the food which, in principle, could form BA after ingestion even if the food product itself does not initially contain high BA levels. In this work we have investigated the production of tyramine and putrescine by Lactobacillus brevis IOEB 9809, of wine origin, under simulated gastrointestinal tract (GIT) conditions.

Results

An in vitro model that simulates the normal physiological conditions in the human digestive tract, as well as Caco-2 epithelial human cell lines, was used to challenge L. brevis IOEB 9809, which produced both tyramine and putrescine under all conditions tested. In the presence of BA precursors and under mild gastric stress, a correlation between enhancement of bacterial survival and a synchronous transcriptional activation of the tyramine and putrescine biosynthetic pathways was detected. High levels of both BA were observed after exposure of the bacterium to Caco-2 cells.

Conclusions

L. brevis IOEB 9809 can produce tyramine and putrescine under simulated human digestive tract conditions. The results indicate that BA production may be a mechanism that increases bacterial survival under gastric stress.

In vivo study of the survival of Lactobacillus delbruecki subsp. bulgaricus CECT 4005T and Streptococcus thermophilus CECT 801 by DVC-FISH after consumption of fermented milk

Direct Viable Count (DVC) method has been recently combined with fluorescent in situ hybridization (FISH) for the specific detection of viable cells of Lactobacillus delbrueckii subsp. bulgaricus CECT 4005T and Streptococcus thermophilus CECT 801. This method has been used to determine their in vitro viability to gastrointestinal juices, being the resistance of L. delbrueckii subsp. bulgaricus and S. thermophilus 26.2% and 9.2%, respectively. On the other hand, an in vivo study has been carried out with the application of this technique for their detection in human feces, after consuming fermented milk. Cells of L. delbrueckii subsp. bulgaricus CECT 4005T were not detected, whereas viable cells of S. thermophilus CECT 801 were detected in a number higher than 10(3) cells per gram in a 30% of the samples after 4 wk of consumption. DVC-FISH is a quick and culture-independent useful method, which has been applied for the 1st time in an in vivo survival study of LAB.