Binding of mutagens by fractions of the cell wall skeleton of lactic acid bacteria on mutagens

Utilization of Peptidoglycans from Lactic Acid Bacterial Cell Walls for the Mitigation of Acrylamide and 5-Hydroxymethylfurfural

Acrylamide (AA) and 5-hydroxymethylfurfural (HMF), which are potentially carcinogenic to humans, are often produced during the hot processing of foods. This study first used a molecular docking model to simulate the binding behavior of four lactic acid bacteria peptidoglycans (PGNs) to AA/HMF, and the binding rate of LAB-based PGNs to AA/HMF was evaluated in vitro. In silico results show that interaction energy is the driving force responsible for the adsorption of LAB-derived PGNs to AA/HMF. In vitro results showed that the PGN of B. lactis B1-04 bound the most AA (28.7%) and HMF (48.0%), followed by L. acidophilus NCFM, B. breve CICC 6079, and L. plantarum CICC 22135. Moreover, an AA/HMF-bound layer on the cell surface of B. lactis B1-04 was observed via AFM and SEM due to adsorption. XPS analysis indicated the removal rate of AA/HMF by selected strains was positively correlated with the proportion of C-O, C=O, and N-H groups of PGNs. The atoms O1, O2, O3, O4, N1, N2, N3, H1, and H2 are involved in the adsorption of LAB-based PGNs to AA/HMF. Thus, the PGNs derived from these four Lactobacillus strains can be regarded as natural adsorbents for the binding of AA/HMF.

Antimutagenic Activity as a Criterion of Potential Probiotic Properties

The antimutagenic activity of probiotic strains has been reported over several decades of studying the effects of probiotics. However, this activity is rarely considered an important criterion when choosing strains to produce probiotic preparations and functional food. Meanwhile, the association of antimutagenic activity with the prevention of oncological diseases, as well as with a decrease in the spread of resistant forms in the microbiota, indicates its importance for the selection of probiotics. Besides, an antimutagenic activity can be associated with probiotics' broader systemic effects, such as geroprotective activity. The main mechanisms of such effects are considered to be the binding of mutagens, the transformation of mutagens, and inhibition of the transformation of promutagens into antimutagens. Besides, we should consider the possibility of interaction of the microbiota with regulatory processes in eukaryotic cells, in particular, through the effect on mitochondria. This work aims to systematize data on the antimutagenic activity of probiotics and emphasize antimutagenic activity as a significant criterion for the selection of probiotic strains.

Biotechnological and Medical Aspects of Lactic Acid Bacteria Used for Plant Protection: A Comprehensive Review

The use of chemical pesticides in agriculture goes hand in hand with some crucial problems. These problems include environmental deterioration and human health complications. To eliminate the problems accompanying chemical pesticides, biological alternatives should be considered. These developments spark interest in many environmental fields, including agriculture. In this review, antifungal compounds produced by lactic acid bacteria (LABs) are considered. It summarizes the worldwide distribution of pesticides and the effect of pesticides on human health and goes into detail about LAB species, their growth, fermentation, and their antifungal compounds. Additionally, interactions between LABs with mycotoxins and plants are discussed.

Cell components, interaction types and functional groups involved in the in vitro binding of bisphenol A by Lactiplantibacillus plantarum RS20D and DL7X

AIMS

The current study aimed to evaluate the capacity of two Lactiplantibacillus plantarum strains to remove Bisphenol A (BPA) and to determine the preliminary removal mechanisms underlying this process.

METHODS AND RESULTS

The BPA removal capacity of L. plantarum RS20D and DL7X was assessed by HPLC analysis. The effect of various treatments (physical, chemical, and enzymatic) on two strains were studied to understand which interaction types worked. The different cellular components of them were also subjected to binding assays. Additionally, Fourier-transform infrared spectroscopy (FTIR) was performed to identify the functional groups related to the BPA binding process. Results show that various treatments enhanced the binding capacity of two strains, the effect of sodium dodecyl sulfate was the most outstanding (P=0.000, P=0.000). Hydrogen bonding and hydrophobic interactions likely occurred. Peptidoglycans showed the highest binding capability, protoplasts and teichoic acids might also exert a binding effect. -OH, C=O, -CH, -NH, C-N, C-O, and P=O participated in BPA binding by the two L. plantarum lines.

CONCLUSIONS

Peptidoglycans, protoplasts, and teichoic acid played a vital role in the binding of BPA.

SIGNIFICANCE AND IMPACT OF THE STUDY

Our results provided a theoretical foundation for developing effective dietary strategies with foodborne L. plantarum to remove food contaminants.

The function and mechanism of lactic acid bacteria in the reduction of toxic substances in food: a review

N-nitrosamines, heterocyclic amines, polycyclic aromatic hydrocarbons, biogenic amines, and acrylamide are widely distributed and some of the most toxic substances detected in foods. Hence, reduction of these substances has attracted worldwide attention. Lactic acid bacteria (LAB) inoculation has been found to be an effective way to reduce these toxic substances. In this paper, the reduction of toxic substances by LAB and its underlying mechanisms have been described through the review of recent studies. LAB aids this reduction via different mechanisms. First, it can directly decrease these harmful substances through adsorption or degradation. Peptidoglycans on the cell wall of LAB can bind to heterocyclic amines, acrylamide, and polycyclic aromatic hydrocarbons. Second, LAB can indirectly decrease the content of toxic substances by reducing their precursors. Third, antioxidant properties of LAB also contribute to the reduction in toxic substances. Finally, LAB can suppress the growth of amino acid decarboxylase-positive bacteria, thus reducing the accumulation of biogenic amines and N-nitrosamines. Therefore, LAB can contribute to the decrease in toxic substances in food and improve food safety. Further research on increasing the reduction efficiency of LAB and deciphering the mechanisms at a molecular level needs to be carried out to obtain the complete picture.

Yogurt consumption and colorectal cancer incidence and mortality in the Nurses' Health Study and the Health Professionals Follow-Up Study

BACKGROUND

Yogurt is a commonly consumed fermented food. Regular yogurt consumption may contribute to a favorable gut microbiome and gut health, but few epidemiologic studies have considered the relation between regular yogurt consumption and the incidence of and mortality from colorectal cancer.

OBJECTIVES

We used data from 2 large, prospective cohort studies, the Nurses' Health Study and the Health Professionals Follow-Up Study, to examine the role of yogurt consumption on colorectal cancer incidence and mortality.

METHODS

During 32 years of follow-up in 83,054 women (mean age at baseline, 45.7 years) and 26 years of follow-up in 43,269 men (mean age at baseline, 52.3 years), we documented a total of 2666 newly diagnosed cases of colorectal cancer in these cohorts. We modeled yogurt consumption at baseline and cumulatively updated it throughout follow-up. Results: Baseline yogurt consumption was associated with a reduced risk of colon cancer in age-adjusted analyses (P for trend < 0.001). Associations remained statistically significant after adjusting for potential confounders, including calcium and fiber intake (P for trend = 0.03), and were restricted to proximal colon cancer. The consumption of 1 + servings per week of yogurt at baseline, compared to no yogurt consumption, was associated with a multivariable HR of 0.84 (95% CI, 0.70-0.99; P trend = 0.04) for the proximal colon cancer incidence. Latency analyses suggested that the most important window of opportunity for regular yogurt consumption to prevent colorectal cancer was 16-20 years in the past. When yogurt consumption was cumulatively updated, associations attenuated and were no longer significant. No statistically significant inverse trend was observed between yogurt consumption and the colorectal cancer mortality.

CONCLUSIONS

In these large cohorts, the frequency of yogurt consumption was associated with a reduced risk of proximal colon cancer with a long latency period. No significant inverse trend was observed for colorectal cancer mortality.

Protective role of lactic acid bacteria and yeasts as dietary carcinogen-binding agents - a review

The importance of food contaminants in the link between diet and cancer has been widely demonstrated. Therefore, different physical and chemical strategies for the control of human exposure to such dietary carcinogens has been explored; however, most of these strategies are complex, costly, and have low efficiency which limited their applications. Hence, microbiological methods have been receiving more attention. Recent in vitro and in vivo studies have indicated that lactic acid bacteria (LAB) and yeast may act as dietary carcinogen-binding agents. This review describes the promising protective role of strains belonging mainly to the Lactobacillus, Bifidobacterium and Saccharomyces genera by acting as dietary carcinogen-binding agents. This property suggests that these microorganisms may have a protective role by reducing the bioaccessibility of dietary carcinogens, thereby decreasing their toxic effects. The mechanisms by which the binding process takes place have not been completely elucidated; thus, the possible underlying mechanisms and factors influencing carcinogens-binding will be addressed.

Effects of Six Different Starter Cultures on Mutagenicity and Biogenic Amine Concentrations in Fermented Sausages Treated with Vitamins C and E

This study was performed to determine changes in mutagenicity and biogenic amine concentrations in sausages fermented with six different starter cultures treated with vitamins C and E. Six different types of fermented sausages with different combination of starter cultures were manufactured. T1, Pediococcus acidilactici; T2, P. pentosaceus and Staphylococcus carnosus; T3, S. carnosus, S. xylosus, Debaryomyces hansenii, Lactobacillus curvatus, and P. pentosaceus; T4, S. carnosus and L. sakei; T5, S. xylosus and L. plantarum; and T6, Penicillium nalgiovensis. After treatment with vitamins C and E in fermented sausages, changes in mutagenicity and biogenic amine concentrations were measured. The sausages fermented with Staphylococcus xylosus and Lactobacillus plantarum starter cultures showed the most effective antimutagenic activity (p<0.05). The mutagenicity was further decreased in the sausages treated with vitamins C and E (p<0.05), regardless of the starter cultures. The use of Pediococcus acidilactici, S. xylosus, L. plantarum, and Penicillium nalgiovensis as starter cultures was effective in decreasing biogenic amine concentrations (p<0.05). In addition, vitamin E was more effective in decreasing the biogenic amine concentrations than vitamin C. In conclusion, we recommend the use of S. xylosus and L. plantarum as starter cultures, in addition to the use of vitamins C and E, to reduce the potential risk of meat mutagens in fermented sausages.

The efficiency of lactic acid bacteria against pathogenic fungi and mycotoxins

Mycotoxins are produced by some fungal species of the genera Aspergillus, Penicillium, and Fusarium and are common contaminants of a wide range of food commodities. Numerous strategies are used to minimise fungal growth and mycotoxin contamination throughout the food chain. This review addresses the use of lactic acid bacteria, which can inhibit fungal growth and participate in mycotoxin degradation and/or removal from contaminated food. Being beneficial for human and animal health, lactic acid bacteria have established themselves as an excellent solution to the problem of mycotoxin contamination, yet in practice their application in removing mycotoxins remains a challenge to be addressed by future research.

Ochratoxin A reduction ability of biocontrol agent Bacillus subtilis isolated from Korean traditional fermented food Kimchi

In the present study, a new biocontrol strain, Bacillus subtilis KU-153, was isolated from the Korean traditional fermented food Kimchi and evaluated for its ability to reduce the ochratoxin A (OTA) content in culture medium. A 16 S rRNA gene sequencing analysis revealed the identity of newly isolated strain KU-153 as B. subtilis. The growth kinetic study of B. subtilis KU-153, in terms of the OTA reduction in culture medium, confirmed its biocontrol efficacy. To verify its ability to reduce the OTA content in culture medium, bacterial extracts (intracellular and extracellular) of B. subtilis were separated and compared with whole B. subtilis cells (viable and heat-killed). No reduction in the OTA content was observed in culture medium with extracellular and intracellular extracts, while viable and heat-killed cells of B. subtilis showed significant levels (p < 0.05) of OTA reduction in culture medium. Interestingly, B. subtilis heat-treated cells showed a higher OTA reduction (45%) than viable cells (22%). Further, B. subtilis heat-treated cells were assessed for their ability to reduce OTA levels in artificially contaminated red wine samples that resulted in an OTA reduction of approximately 90%, suggesting the biocontrol potential of the newly isolated strain B. subtilis KU-153 on OTA reduction.

A comparative study of procedures for binding of aflatoxin M1 to Lactobacillus rhamnosus GG

Several strains of lactic acid bacteria (LAB), frequently used in food fermentation and preservation, have been reported to bind different types of toxins in liquid media. This study was carried out to investigate the effect of different concentrations of Lactobacillus rhamnosus GG (ATCC 53103) to bind aflatoxin M1 (AFM1) in liquid media. AFM1 binding was tested following repetitive washes or filtration procedures in combination with additional treatments such as heating, pipetting, and centrifugation. The mixture of L. rhamnosus GG and AFM1 was incubated for 18h at 37°C and the binding efficiency was determined by quantifying the unbound AFM1 using HPLC. The stability of the complexes viable bacteria-AFM1 and heat treated bacteria-AFM1 was tested. Depending on the bacterial concentration and procedure used, the percentages of bound AFM1 by L. rhamnosus GG varied from as low as undetectable to as high as 63%. The highest reduction in the level of unbound AFM1 was recorded for the five washes procedure that involved heating and pipetting. Results also showed that binding was partially reversible and AFM1 was released after repeated washes. These findings highlight the effect of different treatments on the binding of AFM1 to L. rhamnosus GG in liquid matrix.

Detoxification of cancerogenic compounds by lactic acid bacteria strains

Carcinogens in food are an important issue that threat people's health right now. Lactic acid bacteria (LAB) strains as well-known probiotics have shown numerous perspectives in being used as a good food additive to confront cancerogenic compounds in recent years. Some LAB strains can remove cancerogenic compounds from medium environment via direct physical binding and avoid re-pollution of poisonous secondary metabolites which are generated from degradation of cancerogenic compounds. This article presents a whole overview of the physical-binding of LAB strains to such common cancerogenic compounds existed in food and feed environments as mycotoxins, polycyclic aromatic hydrocarbons (PAHs), heterocyclic amines (HAs) and pthalic acid esters (PAEs).In most cases, summaries of these published researches show that the binding of LAB strains to cancerogenic compounds is a physical process. Binding sites generally take place in cell wall, and peptidoglycan from LAB cells is the chief binding site. The adsorption of lactic acid bacteria to cancerogenic compounds is strain-specific. Specially, the strains from the two genera Lactobacillus and Bifidobacterium show a better potential in binding cancerogenic compounds. Moreover, we firstly used molecular dynamic computer model as a highly potential tool to simulate the binding behavior of peptidoglycan from Lactobacillus acidophilus to DBP, one of pthalic acid esters with genetic toxicity. It was seen that the theoretical data were quite consistent with the experimental results in terms of the ability of this bacterium to bind DBP. Also, the toxicity reduction of cancerogenic compounds by LAB strains could be achieved either in gastrointestinal model or animal tests and clinical researches as well. In conclusion, carefully selected LAB strains should be a good solution as one of safety strategies to reduce potential risk of cancerogenic compounds from food-based products.

Protective Effect of a Lactobacillus salivarius Strain of Human Origin

The protective effect of a Lactobacillus salivariusstrain from human faeces (HA8) was evaluated against the cytotoxicity of N-nitrosodimethylamine (NDMA), N-nitrosopyrrolidine (NPYR), N-nitrosodibutylamine (NDBA) and N-nitrosopiperidine (NPIP) by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. L. salivariusHA8 strain showed a moderate protective effect against NPYR and weak against NDBA and NPIP. No protective effect against cytotoxicity of NDMA was observed at the bacterial population used. To test the effect of L. salivariusHA8 on cytokine production (interleukin-1 ± (IL-1 ±), interleukin-8 (IL-8) and tumour necrosis factor alpha (TNF-≥)), the human macrophage cell line (THP-1) was cultured in the presence and absence of lipopolysaccharide (LPS). L. salivariusHA8 induced IL-1 ±, IL-8 and TNF-≥ releases when cells were stimulating with and without LPS.

The adsorption of ochratoxin a by lactobacillus species

The objective of this study was to examine ochratoxin A (OTA) binding by three lactic acid bacteria (LAB) species: Lactobacillus plantarum, L. brevis, and L. sanfranciscensis. Experiments were conducted using MRS medium and PBS buffer contaminated with 1000 ng/mL OTA and inoculated with live or thermally inactivated bacterial biomass at a concentration of 1 or 5 mg dry weight/mL. It was found that, depending on the strain and biomass density, live bacterial cells reduced OTA content by 16.9% to 35% in MRS medium and by 14.8% to 26.4% in PBS after 24 h of contact. OTA binding was higher in the case of thermally inactivated bacterial biomass (46.2% to 59.8%). The process is very rapid: OTA was removed from PBS as early as after 30 min of contact. The binding of the toxin by cells was partially reversible under the treatment by water and 1 M HCl. The results show that OTA is adsorbed to the surface structures of the cell wall, which is promoted not only by the hydrophobic properties of the cell wall, but also by electron donor-acceptor and Lewis acid-base interactions.

A potential role of probiotics in colorectal cancer prevention: review of possible mechanisms of action

A number of investigations, mainly using in vitro and animal models, have demonstrated a wide range of possible mechanisms, by which probiotics may play a role in colorectal cancer (CRC) prevention. In this context, the most well studied probiotics are certain strains from the genera of lactobacilli and bifidobacteria. The reported anti-CRC mechanisms of probiotics encompass intraluminal, systemic, and direct effects on intestinal mucosa. Intraluminal effects detailed in this review include competitive exclusion of pathogenic intestinal flora, alteration of intestinal microflora enzyme activity, reduction of carcinogenic secondary bile acids, binding of carcinogens and mutagens, and increasing short chain fatty acids production. Reduction of DNA damage and suppression of aberrant crypt foci formation have been well demonstrated as direct anti-CRC effects of probiotics on intestinal mucosa. Existing evidence clearly support a multifaceted immunomodulatory role of probiotics in CRC, particularly its ability to modulate intestinal inflammation, a well known risk factor for CRC. The effectiveness of probiotics in CRC prevention is dependent on the strain of the microorganism, while viability may not be a prerequisite for certain probiotic anticancer mechanisms, as indicated by several studies. Emerging data suggest synbiotic as a more effective approach than either prebiotics or probiotics alone. More in vivo especially human studies are warranted to further elucidate and confirm the potential role of probiotics (viable and non-viable), prebiotics and synbiotics in CRC chemoprevention.

Potential of probiotics, prebiotics and synbiotics for management of colorectal cancer

Colorectal Cancer (CRC) is the second leading cause of cancer-related mortality and is the fourth most common malignant neoplasm in USA. Escaping apoptosis and cell mutation are the prime hallmarks of cancer. It is apparent that balancing the network between DNA damage and DNA repair is critical in preventing carcinogenesis. One-third of cancers might be prevented by nutritious healthy diet, maintaining healthy weight and physical activity. In this review, an attempt is made to abridge the role of carcinogen in colorectal cancer establishment and prognosis, where special attention has been paid to food-borne mutagens and functional role of beneficial human gut microbiome in evading cancer. Further the significance of tailor-made prebiotics, probiotics and synbiotics in cancer management by bio-antimutagenic and desmutagenic activity has been elaborated. Probiotic bacteria are live microorganisms that, when administered in adequate amounts, confer a healthy benefit on the host. Prebiotics are a selectively fermentable non-digestible oligosaccharide or ingredient that brings specific changes, both in the composition and/or activity of the gastrointestinal microflora, conferring health benefits. Synbiotics are a combination of probiotic bacteria and the growth promoting prebiotic ingredients that purport "synergism."

Lactic acid bacteria in the inhibition of Fusarium graminearum and deoxynivalenol detoxification

AIMS

Considering the agronomic and industrial damage that is caused by the fungus Fusarium graminearum, as well as the serious health risks it poses to humans and animals exposed to F. graminearum-produced mycotoxin deoxynivalenol (DON), this study evaluated the ability of different lactic acid bacteria (LAB) strains to inhibit fungal development and remove DON in vitro.

METHODS AND RESULTS

The antagonistic effects of strains and commercial cultures of LAB were evaluated against F. graminearum IAPAR 2218 by the agar diffusion method. Additionally, the influence of the culture media, pH and the presence of lactic and acetic acid on these effects was tested. The capacity to remove DON by viable cells and heat-inactivated cells was analysed in liquid media and quantified by high performance liquid chromatography (HPLC). All isolated strains and commercial cultures inhibited the fungus and removed DON. The pH and culture media concentration did not influence these abilities, but heat inactivation had a strong effect on the ability of bacteria to remove mycotoxin.

CONCLUSIONS

The isolated bacteria are able to inhibit F. graminearum growth and remove DON in vitro.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study suggests potential application of the isolated LAB strains in the inhibition of F. graminearum IAPAR 2218 and DON removal in vitro.

Novel perspectives in probiotic treatment: the efficacy and unveiled mechanisms of the physiological functions

Probiotics are defined as "live microorganisms which confer a health benefit on the host" when administered in adequate amounts, and have potential effects for maintaining intestinal development, nutrition, and treating intestinal inflammations, functional disorders, and other extra-intestinal diseases. Although the benefits of probiotics for human health were first noted over 100 years ago, the analysis of probiotic functions began in earnest only 20 years ago. Probiotics, such as some strains of Lactobacillus, Bifidobacterium, Escherichia coli, and Bacillus subtilis, inhibit the growth of pathogenic bacteria, induce competitive effects for the adherent of pathogenic bacteria and their toxins to intestinal epithelia, induce cytoprotective heat shock proteins, enhance the intestinal barrier function, and modulate the host immune responses. The crosstalk between the host and the probiotics appears to be mediated by bacteria-derived effectors, which can be sensed with multiple systems, including the Toll-like receptors and cell membrane transporters. Future analyses will identify more probiotic-derived effectors, the recognition mechanisms of these effectors, and the subsequent changes of the intestinal epithelia and immune cells for each probiotic treatment. For clinical use, a procedure that objectively evaluates the ability of each probiotic effect will help establish a standard for choosing the most valuable strain and its proper dose for each individual patient.

Binding of mutagens to exopolysaccharide produced by Lactobacillus plantarum mutant strain 301102S

Exopolysaccharide (EPS) was produced by Lactobacillus plantarum 301102 on exposure to the mutagenic action of acridine orange and novobiocin. The biological characteristics of this mutant strain 301102S were the same as those of the parent strain, but fermented milk prepared with the mutant strain showed antimutagenic activity on 3-amino-1,4-dimethyl-5H-pyrido indole. Only EPS-bound cells of strain 301102S showed binding ability to mutagens such as heterocyclic amines, and the mutagens were inactivated by binding to EPS. The binding ability was affected by pH; the greatest percentage binding was noted at pH 8.0. Addition of Mg(2+) and sodium dodecyl sulfate, but not oxgall, inhibited the binding ability. Therefore, the binding mechanism of the EPS may consist of ion-exchange and hydrophobic bonds, and the EPS would bind mutagens in the intestine.

Roles of probiotics and prebiotics in colon cancer prevention: Postulated mechanisms and in-vivo evidence

Probiotics are live bacteria that could exert health beneficial effects upon consumption. In additional to their conventional use as gut modulators, probiotics are investigated for their role to prevent cancer. In-vivo and molecular studies have demonstrated encouraging outcomes, mainly attributed to its antimicrobial effects against carcinogen-producing microorganisms, antimutagenic properties, and alteration of the tumor differentiation processes. Prebiotics are indigestible food components that could promote the growth of beneficial bacteria including probiotics. Present studies have suggested that prebiotics also possess protective effect against colon carcinogenesis, mainly attributed to the production of short chain fatty acids upon its fermentation by gut microflora, and alteration of gene-expressions in tumor cells. Synbiotic (combination of probiotic and prebiotic) has been found to exert a synergistic effect in improving colon carcinogenesis compared to when both were used individually. This paper highlights the colon cancer preventive effects by probiotics, prebiotics and synbiotics. In addition, the controversial outcomes on the insignificant effect of these food adjuncts will be discussed.

Binding of heterocyclic aromatic amines by lactic acid bacteria: results of a comprehensive screening trial

Aim of the present study was a comprehensive investigation of the detoxification capacities of lactic acid bacteria (LAB) towards heterocyclic aromatic amines (HCA) formed during cooking of meat. It has been postulated that LAB prevent genotoxic and/or carcinogenic effects of HCA in laboratory rodents and humans via direct binding mechanisms. We measured the removal of the most abundant cooked food mutagens (AalphaC, PhIP, IQ, MeIQx, DiMeIQx) by eight LAB species. From each species, twelve strains were tested in liquid binding experiments with HPLC coupled with coulometric electrode array detection. The highest removal rates were observed with the representatives of the L. helveticus and S. thermophilus groups, which were seven to eight times more effective than L. kefir and L. plantarum. Strong and statistically significant differences were seen in the binding behaviour of the individual amines, the ranking order of detoxification being AalphaC > DiMeIQx > MeIQx > IQ > PhIP. Results of Salmonella/microsome assays with strain TA98 showed that the binding of AalphaC and PhIP to LAB correlates with the reduction of their mutagenic activities. This study may contribute to the development of strategies concerning the adverse health effects of HCA utilizing highly protective LAB for the production of fermented foods.

In vitro removal of ochratoxin A by wine lactic acid bacteria

A study was carried out to determine the in vitro interaction between ochratoxin A (OTA) and wine lactic acid bacteria (LAB). Fifteen strains belonging to five relevant oenological LAB species were grown in liquid synthetic culture medium containing OTA. The portion of OTA removed during the bacterial growth was 8 to 28%. The OTA removed from the supernatants was partially recovered (31 to 57%) from the bacterial pellet. Cell-free extracts of three representative strains were produced by disrupting cells in a French pressure cell. The ability of crude cell-free extracts to degrade OTA was studied. OTA was not degraded by cell-free extracts of wine LAB strains, and no degradation products of OTA were detected in the high-performance liquid chromatograms of the methanol extract of the bacterial pellet. On the basis of these results, we conclude that OTA removal by wine LAB is a cell-binding phenomenon. The chemistry and the molecular basis of OTA binding to wine LAB remains unknown.

Binding of Fusarium mycotoxins by fermentative bacteria in vitro

AIMS

Fusarium toxins can occur in conserved forages impairing farm animal performances and health. On-farm biological decontamination methods could be an alternative to traditional physico-chemical methods. In this work, the ability to remove Fusarium toxins by fermentative bacteria was evaluated in vitro.

METHODS AND RESULTS

Twenty-nine strains of lactic (LAB) and propionic acid bacteria (PAB) were tested for their ability to remove deoxynivalenol (DON) and fumonisins B1 and B2 (FB1, FB2) from an acid, pH 4, medium. Mycotoxin removal was widespread for LAB, but differences among strains were large. Removal was up to 55% for DON, 82% for FB1 and 100% for FB2. Selected strains were also capable of removing up to 88% zearalenone. The PAB strains were less efficient than the LAB. Binding, not biodegradation appeared to be the mode of action, as no toxin derivatives were observed and removal was not impaired in nonviable bacteria. Binding was not affected by pH, except for fumonisins that decreased to nearly 0% at neutral pH.

CONCLUSIONS

Selected fermentative bacteria are able to bind main Fusarium mycotoxins.

SIGNIFICANCE AND IMPACT OF THE STUDY

The binding ability of selected strains could be used to decrease the bioavailability of toxins in contaminated silages.

Molecular identification of monomeric aspartate racemase from Bifidobacterium bifidum

Bifidobacterium bifidum is a useful probiotic agent exhibiting health-promoting properties and contains d-aspartate as an essential component of the cross-linker moiety in the peptidoglycan. To help understand D-aspartate biosynthesis in B. bifidum NBRC 14252, aspartate racemase, which catalyzes the racemization of D- and L-aspartate, was purified to homogeneity and characterized. The enzyme was a monomer with a molecular mass of 27 kDa. This is the first report showing the presence of a monomeric aspartate racemase. Its enzymologic properties, such as its lack of cofactor requirement and susceptibility to thiol-modifying reagents in catalysis, were similar to those of the dimeric aspartate racemase from Streptococcus thermophilus. The monomeric enzyme, however, showed a novel characteristic, namely, that its thermal stability significantly increased in the presence of aspartate, especially the D-enantiomer. The gene encoding the monomeric aspartate racemase was cloned and overexpressed in Escherichia coli cells. The nucleotide sequence of the aspartate racemase gene encoded a peptide containing 241 amino acids with a calculated molecular mass of 26 784 Da. The recombinant enzyme was purified to homogeneity and its properties were almost the same as those of the B. bifidum enzyme.

Fermented milks, probiotic cultures, and colon cancer

Colorectal cancer (CRC) is a major cause of death from cancer in the Western world. Approximately 70% of CRC is associated with environmental factors, probably mainly the diet. There is interest in the potential protective role of fermented milks containing probiotic cultures against CRC. This article analyzes the existing data from human, animal, and in vitro studies that explore whether consumption of milks fermented with probiotic cultures could play a role in colon cancer risk reduction. Cohort studies have failed to detect significant effects, but most case-control studies favor a protective role of fermented milks against colon cancer. Interventional studies have shown a shift of intermediate markers of CRC risk in human subjects from a high- to low-risk pattern after ingestion of fermented milks or probiotics. Animal studies consistently show a reduction in chemically induced colorectal tumor incidence and aberrant crypt formation accompanying probiotic administration. In vitro studies also provide evidence of protection, and permit a better understanding of active compounds involved, and of the mechanisms underlying their anticarcinogenic effects. Probiotics may beneficially modulate several major intestinal functions: detoxification, colonic fermentation, transit, and immune status, which may accompany the development of colon cancer. Although the evidence is not conclusive and much further research is required, the data reviewed constitute a promising body of evidence supporting the protective role of milks fermented with probiotic cultures in colon cancer risk reduction.

Determinations of the antimutagenic activities of several probiotic bifidobacteria under acidic and bile conditions against benzo[a]pyrene by a modified Ames test

Antimutagenic activities of six bifidobacteria, after acidic and bile treatment mimicking gastrointestinal conditions, against benzo[a]pyrene (B[a]P) were determined by a modified Ames test using Salmonella typhimurium TA 100. Results showed that when bifidobacteria were treated at pH 2.0 for 3 h or 1% bile for 6 h, their antimutagenic activities against B[a]P were increased as compared to controls at pH 7.0 for 0 h. After sequential acidic pH and bile treatments, Bifidobacterium lactis Bb-12 displayed the highest antimutagenic activity (71.5%), although its viable cell number was less than 2.0 log cfu/ml. The antimutagenic activity of B. lactis Bb-12 against B[a]P was increased as pH values were increased from 2.0 to 7.0, and reaction time was extended from 1 to 3 h. However, antimutagenic activity was decreased as bile salt concentration was increased from 0.5% to 2.0%. The antimutagenic activity of B. lactis Bb-12 against B[a]P was increased in the presence of whole milk (WM), semiskimmed milk (SSM) and skimmed milk (SM). When B. lactis Bb-12 was preincubated with B[a]P and milk substrates, its antimutagenic activity was increased to 99-100%.

Binding of aflatoxin B1 to cell wall components of Lactobacillus rhamnosus strain GG

The surface of Lactobacillus rhamnosus strain GG (LGG) has previously been shown to bind aflatoxin B(1) (AFB(1)) effectively, it being a food-borne carcinogen produced by certain species of Aspergillus fungi. To establish which components of the cell envelope are involved in the AFB(1) binding process, exopolysaccharides and a cell wall isolate containing peptidoglycan were extracted from LGG and its AFB(1) binding properties were tested. LGG was also subjected to various enzymatic and chemical treatments and their effects on the binding of AFB(1) by LGG were examined. No evidence was found for exopolysaccharides, cell wall proteins, Ca(2+) or Mg(2+) being involved in AFB(1) binding. The AFB(1) binding activity of the cell wall isolate indicates that AFB(1) binds to the cell wall peptidoglycan of LGG or compounds tightly associated with the peptidoglycan.

Binding activity of natto (a fermented food) and Bacillus natto isolates to mutagenic-carcinogenic heterocyclic amines

The fermented food, whole meal Natto, viscous polymeric material from Natto, Natto bean, cooked soya bean, and 28 bacterial isolates from Natto were studied for their binding capacity to foodborne mutagenic-carcinogenic heterocyclic amines. The mutagenic heterocyclic amines used were Trp-P-1 (3-amino-1,4-dimethyl-5H-pyrido(4,3-b)indole); Trp-P-2 (3-amino-1-methyl-5H-pyrido(4,3-b)indole); Glu-P-1 (2-amino-6-methyldipyrido(1,2-a:3'2'-d)imidazole); PhIP (2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine); IQ (2-amino-3-methylimidazo(4,5-f)quinoline); MeIQ (2-amino-3,4-dimethylimidazo(4,5-f)quinoxaline); MeIQx (2-amino-3,8-dimethylimidazo(4,5-f)quinoxaline); and MeAalphaC (2-amino-3-methyl-9H-pyrido(2,3)indole). The lyophilized Natto and other fractions of Natto exhibited high binding activity towards Trp-P-1, Trp-P-2, PhIP, and MeAalphaC, while Glu-P-1, IQ, and MeIQ were not effectively bound. The binding capacity of bacterial isolates (Bacillus natto) were isolate-mutagen dependent. Heat treated lyophilized cells, cell wall, and cytoplasmic contents of the bacterial isolate with the highest binding capacity were analyzed for their ability to bind different heterocyclic amines. The results indicate the importance of the cell wall in binding to heterocyclic amines, whereas the cytoplasmic contents were less effective. Heat-treated cells were not much different from that of viable cells in their binding. The impact of different factors, such as pH, incubation time, metal ions, different concentrations of sodium chloride and alcohol, various enzymes, and acetylation of mutagens on binding of Trp-P-1 and IQ, were discussed. The significance of the present results is also discussed from the viewpoint that Natto, a fermented food, is able to scavenge dietary mutagenic heterocyclic amines through binding.