Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555, Japan
|Received October 1, 2012; Revised October 20, 2012; Accepted October 29, 2012|
|In Japan, milk and food companies have recently developed many functional yogurts using selected probiotic lactic acid bacteria (LAB) and Bifidobacterium strains. In 1991, the FOSHU (foods for specified health uses) system began instituted by the Ministry of Health, Labor and Welfare. In 2010, approximately 1,000 commercially available items were labeled as FOSHU products that are specially given brands showing good health effects for humans. Japanese commercial yogurts are classified into three type categories: fermented using selected probiotics, functional components added, and standard types. Many functions are considered in the selection of probiotics including competitive adhesion exclusion of enteritic pathogens, cholesterol lowering effects, and positive immuno-modulatory effects. Adhesion to the human intestine is one of the most important characteristics of probiotic LAB and bifidobacteria. Our new screening system for adhesive activity involves a combination of three methods: the rat colonic mucin-micro plate assay, the Carnoy’s histochemical staining method, and the carbohydrate probe binding assay. Recently, we developed a new screening assay using the BIACORE biosensor chip coated with human colon mucin (HCM). We found new LAB strains that recognize and specifically bind to the human ABO blood type antigens. We named these “blood type LAB”. We identified the molecular LAB binding mechanism occurring in the human intestine through unique adhesin molecules that are expressed on the bacterial cell surface as lectin-like proteins. Bacteria with strong adhesion ability improve gastrointestinal health by continuous proliferation in the intestine; and increase the chance of intake into the Peyer’s patches through M-cells that inhibit allergies because of LAB immune-stimulating activity. The future Japanese food market will contain superior functional yogurts containing adhesive effective probiotic LAB and bifidobacteria that are expected to be developed using our proposed mass screening system shown here.|
In Japan, milk and food companies have recently developed and sold many types of functional yogurts (fermented milk) using selected probiotics including beneficial bacteria such as lactic acid bacteria (LAB) and Bifidobacterium sp. In 1991, the Ministry of Health, Labor and Welfare developed FOSHU (foods for specified health uses) system, a pioneer in the world for functional foods. First, we would like to introduce briefly the FOSHU system and the representative yogurts. We wish to make choices for probiotics including LAB and bifidobacteria to construct functional yogurts where the method to select good LAB is being eveloped. We would like to introduce the history of our development of a mass screening method using a biosensor BIACORE to select probiotics with high binding activity in the human gut to maintain long term health effects. Recently, we proposed a new strategy for the application of our selected human blood type LAB against inflammatory bowel disease (IBD); and I would like to introduce this proposal briefly.
The concept of the foods for specified health uses (FOSHU) system developed by the Ministry of Health, Labor and Welfare was introduced in 1991 for the Japanese market. A FOSHU food is permitted to state a beneficial health claim if several strict requirements including human clinical trials are met through government review. The logo for FOSHU is allowed to be shown on the surface of the package (Fig. 1). At present (2011), 983 FOSHU foods are commercially available in Japanese food markets; they are specially labeled brands showing good health effects for humans. Evidence shows FOSHU foods decrease skyrocketing medical bills, preventing diseases such as diabetes, high blood pressure, high blood sugar, and colon cancers.
Fig. 1. Logo of FOSHU issued by the Japanese Government.
The FOSHU system is classified into eight categories as foods for: 1) improving intestinal disorders, 2) lowering high cholesterol, 3) lowering high blood pressure, 4) helping mineral adsorption, 5) overall health improvement, 6) increasing dental health (against dental caries), 7) reducing high blood sugar levels and 8) reducing high body fat levels (against obesity). Category 1 FOSHU contains oligosaccharides, yogurts using LAB or bifidobacteria and dietary fibers. In 2008, the FOSHU market size was 7,000 billion yen (93 billion US dollars) per year. Many Japanese personally feel disorder in gut conditions, because more than 50% of the Japanese FOSHU market size is occupied by Category 1 foods.
Japanese functional yogurts are classified into three groups: 1) functional LAB added, 2) functional added components and 3) the others.
Group 1 yogurts contain specially selected Lactobacillus (Lb.) and/or Bifidobacterium (B.) sp. as shown in Table 1. For instance, a functional yogurt “Onakani GG!: LGG”, the first yogurt permitted as FOSHU, is produced using Lb. rhamnosus GG (LGG) by Takanashi Milk Products Co., Ltd.; permitted by a production license from Valio Co., Ltd., Finland. In every FOSHU yogurt, the registered strain number such as B. longum BB536, Lb. gasseri SP and Lb. casei YIT 9029 Shirota is important information as they are proprietary bacteria selected by each food company. The cost for obtaining a FOSHU brand is estimated to be approximately a billion yen (ca. 1.25 million US dollars) primarily because of obtaining costly human clinical data.
Table 1. Probiotics used in Japanese functional yogurts
The best-selling functional yogurt in Japan is “Probio yogurt LG21” by Meiji Co., Ltd. with sales of more than 200 billion yen (ca. 2.6 billion US dollars) per year continuously for 10 years. The LG21 yogurt may prevent gastric ulcers or stomach cancer by exclusion of Helicobactor pyroli from the stomach of adults. The best-selling LG21 yogurt is ironically not FOSHU branded; however, many Japanese consumers are aware of the FOSHU brand when they purchase yogurts in food shops and supermarkets. A popular functional yogurt in the Japanese market with LG21, is “BIO” (“Activia” is the common name used in the US and EU) produced by Danon Co., Ltd. with many variation types. BIO contains B. animalis subs. lactis BE 80 isolated from animal intestines that may activate the peristaltic movement in the intestine to prevent constipation.
Among the Japanese marketed functional yogurts, the “symbiotic yogurts” such as “Bifiene” type M and S (FOSHU) produced by Yakult Honsha Co., Ltd. are becoming popular. These yogurts contain B. breve Yakult (probiotics) as 100 billion (M) and 300 billion (S) cells in a bottle with Galacto-oligosaccharide (GOS), a prebiotics. The big three FOSHU yogurts as plain types in the Japanese market are: “Megumi” by Megmilk Snow Brand Co., Ltd., “Bifidus yogurt” by Morinaga Milk Industry Co., Ltd., and “Bulgaria yogurt” by Meiji; they use probiotics Lb. gasseri SP+Bifidobacterium SP, B. longum BB536, and Lb. bulgaricus OLL2038+Streptococcus thermophilus OLL1131, respectively.
Group 2 yogurts contain functional food additive components and are popular in the Japanese market. For instance, “Lactoferrin 1000” made by Morinaga Milk Co., Ltd. contains more than 1,000 mg of bovine lactoferrin (bLf) that shows multifunctional bioactivities such as preventing ability of harmful bacteria that require Fe ions and increasing cell proliferation. “Honebuto yogurt” produce by Megmilk Snow Brand contains “MBP (milk basic proteins)” isolated from bovine milk to prevent osteoporosis. “Glucosamin Power yogurt” by Megmilk Snow Brand is a best-selling product through a home-delivery system especially for elderly persons. The yogurt contains more than 1.3 g of N-acetyl glucosamine (GlcNAc) that may relieve joint pain. Recently, “Dr. Piro” produced by Glico Dairy Products Co., Ltd. appeared in the Japanese food market by adding immunoglobulin Y (IgY) as urease (EC 188.8.131.52) antibody from chicken egg yolk that may prevent the adhesion of H. pylori to stomach mucosa or mucous membranes. In Korea, this functional yogurt with added anti-urease IgY was introduced in 2000; e.g., “Will” was produced by Korea Yakult Co. Ltd. and “Gut” by Maeil Milk Co., Ltd etc.
Group 3 contains the other products such as B.G.S., gamma aminobutyric acid (GABA), and lactotripeptides produced using LAB fermentation. The concept contained in the products is based on “Biogenetics” by Dr. T. Mitsuoka (Mitsuoka, 1998). “Onaka Katsuryoku (B.G.S.: Bifidogenic Growth Stimulator)” produced by Meiji contains 1,4-dihydroxy-2-naphtoic acid components (DHNA). DHNA is produced by Propionibacterium fermentation and stimulates Bifidobacterium proliferation as the Bifidus factor. “Pretia” (FOSHU) produced by Yakult contains γ-amino acid produced by Lactococcus lactis that may decrease blood pressure through the repression of adrenalin secretion. “Amiel S” (“Evolas” named in EU) produced by Calpis Co., Ltd. contains lactotripeptide including IPP and VPP produced by Lb. helveticus and may decrease blood pressure by repressing the activity of angiotensin-I converting enzyme.
There are more than 75 FOSHU yogurts at present and they are expected to become more popular in the future Japanese market. Please confer our review or articles of books (Saito, 2004, 2008).
Probiotics are defined as viable bacteria bringing positive health effects to the host by balancing the intestinal flora. Probiotics show three characteristics: 1) resistant to gastric acid, 2) resistant to bile acid, and 3) binding activity to human intestinal tracts. Among the 20 genera of LAB, lactobacilli isolated from the intestines of animals and humans are used as probiotics in functional fermented milk products; and bacteria belonging to the genera Enterococcus, Streptococcus, and Lactococcus have recently been proposed to be probiotics (Kimoto et al., 1999; Ouwehand et al., 2002).
Almost all harmful bacteria can bind to human intestinal mucosa using special adhesin, lectin-like proteins that are located on the top of pilli and bind the receptor sugar portion in human intestinal mucosa, glycoproteins or glycolipids. Adhesive activity to the human intestine is one of the most important characteristics of probiotic LAB and Bifidobacterium that show initial colonization and later proliferation in intestinal tract. To obtain positive immunological activity, incorporation of LAB from M cells, and later stimulation of the entire immune system, much depends on the adhesion ability because of the increased chance of incorporation. The mechanism by which L. acidophilus group LAB adheres to the human gastrointestinal tract, has been partially elucidated (Aleljung et al., 1994; Coconnier et al., 1992; Reid et al., 1993). Mukai et al., (1992) and Yamada et al. (1994) have revealed, from results of hemagglutination assay (HA), the presence of several lectin-like proteins on the cell surfaces of L. acidophilus group LAB.
Such proteinaceous components in the SLP are thought to contribute to cell adhesion through their binding to carbohydrate portions of the colonic mucus layer. Morata de Ambrosini et al. (1999) reported that lectin-like surface molecules of L. casei CRL 431 stimulated the immune system.
Previously, we developed an evaluation system using rat colon mucosa (RCM) isolated from rat colons (using 400-500 rats) as a replacement for the human colon mucosa (HCM), because their chemical structures resemble HCM (Saito, 2004).
Our initial screening system involved a combination of methods using three steps: 1) the rat colonic mucin-micro plate assay, 2) the Carnoy’s histochemical staining method, and 3) the carbohydrate probe binding assay (Fig. 2).
Fig. 2. A proposed mass screening system for probiotic LAB with high adhesion to human intestine. RCM, rat colonic mucin; SLP, surface layer proteins; LAB, lactic acid bacteria (Saito, 2004).
Eight acidic and neutral O-glycosidic (mucin-type) sugar chains that combine with RCM were used (Slominany et al., 1980). The chemical structures of RCM are similar to the structures of those isolated from HCM (Podolsky, 1985). We showed the conventional hemagglutination (HA) test is not suitable for selecting LAB with strong adhesion to the human intestinal tract. We introduced a new screening method using polystyrene beads coated with RCM (Takahashi et al., 1996); and later a modified screening method using RCM-coated microtiter plates without non-specific reaction improving the blocking conditions (Matsumura et al, 1999). The method was shown to be useful as a first step in mass screening the adhesiveness of LAB to the human intestinal tract.
Surface layer proteins (SLP) were prepared from cells of LAB selected by the first mass screening step. The binding of lectin-like protein(s) in SLP to the colonic mucous layer was confirmed using histochemical staining using human colon tissues fixed with Carnoy’s fixative (Takahashi et al., 1996).
We proposed a new method to select LAB using a commercial biotinylated carbohydrate probe that has the representative partial structures of the sugar chains constituting HCM (Saito et al., 2000). High levels of reactivity were detected in 19 strains with a trisaccharide probe that has an A-antigen structure [GalNAcα1-3(Fucα1-2)Galβ1-]. The adhesion evaluation score proposed was also considered to be useful as an indicator for the final selection of a probiotic LAB.
In the literature, a binding assay using Caco-2 cell line (human epithelial colorectal adenocarcinoma) after coincubation with testing bacteria was examined (Lebeer et al., 2012; Maccaferri et al., 2012). The method is difficult where control of binding cell numbers by washing and the results tend to be different depending on each researcher. Also, Caco-2 is a cell line that has some sugar chains with abnormal chemical structures. Therefore, we did not use the Caco-2 cell line. Further, the chemical structures of sugar chains on colon mucin comparing rat and human are not the same. Later, we used real human mucosa prepared from the normal portion of the human colon obtained during colon cancer surgery through the help of our university’s hospital.
Recently, we developed a new screening assay using the biosensor BIACORE 1000 utilizing surface layer plasmon resonance (PSR) with HCM as shown in Fig. 3 (Uchida et al., 2004, 2006a). We performed a mass-screening determining the adhesive activity of 238 LAB strains isolated from the human intestine. We used HCM-A, B and O (BSA-A, B and H; BP-probe A,B and H) individually as ligands to the surface of carboxyl-dextran coated on a sensor chip type CM5. We injected bacterial cells suspended in HBS-EP buffer after lyophilization as the analyte. The sensor chip is considered a para-human intestinal tract and the BIACORE analysis system with the sensor chip also was considered to be a para-colon environment maintained at 37oC under anaerobic conditions. We first developed the ideal evaluation system to select probiotics with strong binding activity to human mucosa using BIACORE. As the system works automatically and the door of the machine is never opened after beginning the experiment, the data cannot be changed unlike the human error that can be introduced in the Caco-2 analysis. From the comparison with the resonance units (RU) on the sensor-gram between human ABO blood type A antigen and B antigen, we found the “blood type LAB” which can recognize the trisaccharide structure and specifically bind to HCM-A stronger than to HCM-B as shown in Fig. 4 (Uchida et al., 2006a, 2006b). We named the bacterium as an “A-type LAB” which can combine trough recognition of human A-type antigen structure. Later, we discovered many strains of B-type LAB and Otype LAB strains in our culture collection of probiotics isolated from the human intestine.
Fig. 3. Sensor chip CM5 coated with human colonic mucin (HCM) for the selection of bacteria with high adhesion activity to human intestine using BIACORE. RU, resonance unit (Uchida et al., 2004).
Fig. 4. Probiotic LAB combines to the human A-antigen structure (Uchida et al., 2006).
The number of patients having pollen allergy has increased in Japan especially among the younger generation. DNA fragments from the genome DNA of strains of LAB were estimated for mitogenic activity using the spleen cells of mouse. In 1995, Krieg et al. reported that CpG 1826 (TCCATGACGTTCCTGACGTT) prepared from the DNA of Escherichia coli showed a strong immunestimulating activity in spleen cells from mice or rabbits (Table 2). We found many types of CpG and AT motifs as immune-stimulative DNA motifs (ODN) in probiotics such as L. rhamnosus GG (LGG), B. longum and L. gasseri; and dairy LAB such as L. bulgaricus and Str. thermophilus. We constructed swine TLR9 transfectants using HEK 293 cells and CHO K-1 cells after introducing the expression vector inserting of the structural gene of swine TLR9 (3,093 bp., 1,030 aa., 115.9 kDa) (Shimosato et al., 2003, 2004). The expression of TLR9 on the surface of transfectants was confirmed using anti-swine TLR9 antibody. Finally, we established a new evaluation system with tranfectants of swine TLR9 containing three steps: 1) DNA intake assay, 2) reporter assay by determining signal transduction of NF-κB, and 3) ELISA assay or real time PCR to determine induction of cytokines such as IL-12 as shown in Fig. 5.
Table 2. Immunostimulatory DNA motif (ODN) isolated from genome DNA of several bacteria
Fig. 5. Establishing a new evaluation system of immune stimulation with transfectant expressing swine TLR9 on the cell surface (Shimosato et al., 2003).
We isolated and identified several adhesins and adhesinlike proteins from blood type LABs that specifically combine with HCM. After extraction of the surface layer proteins (SLP) from cells of the A-type LAB with 1-3 M guanidine hydrochloride (GHCl) solution, the adhesin was isolated from SLP with the ligand fishing method using PVDF membrane covered with BSA-A (human ABO blood type A antigen on bovine serum albumin). In L. crispatus LA1007 and L. brevis OLL2772 (A-type LAB), the primary component was identified in the “S-layer protein (SlpA)” after cloning as a lectin-like protein at 48 kDa (Uchida et al., 2006a) as shown in Fig. 6. In L. casei LA1005 and L. plantarum LA318 (A-type LAB), the primary component was identified as a “glyceraldehyde-3-phosphate-dehydrogenase (GAPDH)” after cloning as a lectin-like protein at 41 kDa (Kinoshita et al., 2008). In L. mucosae LA1001 (A-type LAB), the primary component was identified as the “ABC transporter Cys binding type” after cloning as the lectin-like protein at 29 kDa (Watanabe et al., 2010). We also identified other lectin-like proteins, enolase and elongation factor Tu (EF-Tu) from the SLP of A-type LAB (data not shown).
Fig. 6. Three representative adhesins isolated from the cell surface of blood type LAB that specifically combine to blood type antigens in human colonic mucin.
Recently, Katakura et al. (2010) reported the SLP prepared from Lactococcus lactis IL1403 contained 16 proteins and all were identified as cytoplasmic proteins which recognize yeast mannan. The reason why these proteins including heat shock protein DnaK, GAPDH, 30S ribosomal protein S1, EF-Tu and others exist on the surface is they may be adhesins binding to sugar portions of glycoconjugates and can serve for interaction with another microorganism such as LAB or yeast. In Lactobacillus sp. LA1007 (A-type LAB), three lectin-like proteins (SlpA+GAPDH+ABC transporter) were expressed in SLP at the same time as adhesins (data not shown). Probiotic LABs may combine to the sugar portions of HCM using several adhesins and compete with harmful bacteria in human intestines. Although each adhesin of A-type LAB may be weak, the binding ability as the total sum may become very strong and can compete with or overcome harmful bacteria in the human intestinal environment.
In 2009, Turnbaugh et al. reported obesity is associated with phylum-level changes in the microbiota and reduced bacterial diversity (Nature, 2009). In 2010, Vijay-Kumar et al. reported some intestinal bacteria may cause obesity in rats (Vijay-Kumar et al., 2010). We believe obesity is a disorder caused by a bacterial imbalance between good and harmful bacteria. In 2011, Kadooka et al. reported the regulation of abdominal adiposity is possible using probiotic L. gasseri SBT2055 in rats with obesity tendencies. A yogurt named “Free yogurt Gasseri SP LAB” using this strain is now commercially available in Japan that may reduce obesity.
In 2011, Nagai et al. reported L. bulgaricus OLL2073 R-1 producing an extra-celluler polysaccharide (EPS) reduced the infection rate of influenza virus through the activation of NK cells. The yogurt named “R-1 yogurt” using the strain is being sold in Japan that may prevent influenza and respiratory infections.
Recently, we began investigation for the prevention of ulcerative colitis (UC) using probiotics. Although the reason for UC remains unknown, medical researchers estimate that some harmful intestinal bacteria such as Fusobacterium (F.) varium are candidates for causing UC. F. varium produces butyric acid inducing apoptosis and triggers the crisis of inflammation through the expression of cytokines such as IL-8 leading to UC (Ohkusa et al., 2003). In the preliminary competitive inhibition experiment, the representative harmful bacteria such as Staphylococcus aureus and Escherichia coli isolated from human intestine were inhibited the adhesion to HCM by selected A-type LAB (Fig. 7). We found strains of F. varium isolated from the inflammatory part of a UC patient showed high affinity to A/B-type antigens of HCM. As UC usually climaxes with inflammation in the rectum and sigmoid colon, we therefore selected strains of Bifidobacterium with strong binding activity to HCM-A from our culture collection using the BIACORE assay. In the preliminary competitive inhibition experiment, two strains of F. varium with strong binding activity to HCM-A were inhibited using the A-type Bifidobacterium strains with the micro plate assay. The exclusion experiment for F. varium using A-type Bifidobacterium is getting good results (data not shown). In the very near the future, we will be able to propose a new functional yogurt against UC.
Fig. 7. Competitive inhibition for the adhesion of harmful bacteria by selected blood type LAB on human colonic mucin (HCM).
In 2010, some Bacteroides sp. with porphyranases were discovered in Japanese gut microbiota that may be transferred from marine bacteria Porphyra spp. (Nori) (Hehemann et al., 2010). The reason is speculated to be that Japanese eat seaweeds (NORI) frequently and the gene coding porphyranases must be needed to digest nutritional polysaccharides in Nori. The report suggested to us that some unique and valuable bacteria must exist in human populations of different countries. Although Asians look at the research of the Western countries, we had better pay attention to our countries. Therefore, we hope to collect more information about unique microbiota in Asian environments including animal and human intestines and share the results for each through exchanges with Korean Society for LAB (KSLAB), Japan Society for LAB (JSLAB) and Asian Federation of Society for LAB (AFSLAB).
We thank Prof. Sung-Sik Yoon (President of KSLAB, Yonsei University,) for giving us the chance to write this invited review. This study was in-part supported by a Grant-in-Aid for Scientific Research (B) (2) (No. 223801 44); and for Exploratory Research (No. 18658030) from the Japan Society for the Promotion of Science (JSPS).
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