Strains Of Lactobacillus Bulgaricus Research Articles

Antibiotic Resistance Profile of Indigenous Streptococcus thermophilus and Lactobacillus bulgaricus Strains Isolated from Traditional Yogurt

Antibiotic resistance signifies a safety hazard to public health. Lactic acid bacteria, particularly, Streptococcus thermophilus and Lactobacillus bulgaricus, are useful organisms responsible for dairy fermentation. In keeping with this, they may transfer antibiotic resistance to human population. We conducted a study exanimated the antibiotic resistance pattern and distribution of antibiotic resistance genes of the S. thermophilus and L. bulgaricus strains isolated from traditional yogurt samples. Fifty-five traditional yogurt samples were collected, and S. thermophilus and L. bulgaricus strains were isolated using the microbial culture. The disk diffusion method in agar wells was utilized to assess the antibiotic resistance pattern of isolates against 13 antibiotic agents. The distribution of antibiotic resistance genes was assessed using conventional PCR. Lactobacillus bulgaricus and S. thermophilus were identified in 94.54% (52/55) and 87.27% (48/55) of yogurt samples, respectively. Both L. bulgaricus and S. thermophilus bacteria were simultaneously identified in 72.72% of samples. Streptococcus thermophilus isolates harbored the highest antibiotic resistance rate against tetracycline (31.25%), ampicillin (31.25%), gentamicin (25%), erythromycin (25%), penicillin (12%), and ciprofloxacin (20.83%). Lactobacillus bulgaricus isolates harbored the highest resistance rate against tetracycline (9.61%), ampicillin (9.61%), gentamicin (9.61%), and erythromycin (7.69%). Streptococcus thermophilus (33.33%) isolates harbored the higher distribution of multidrug resistance than L. bulgaricus (11.53%). aacA-D (20.83%), tetK (16.66%), ermA (14.58%), blaZ (14.58%), and gyrA (12.50%) were the most commonly detected antibiotic resistance genes in S. thermophilus. AacA-D (3.84%) and tet K (3.84%) were the most commonly detected antibiotic resistance genes in L. bulgaricus. Lactobacillus bulgaricus isolates did not harbor tetM, cat1, rpoB, vanA, linA, and strA-strB antibiotic resistance genes. Streptococcus thermophilus and L. bulgaricus strains used in traditional yogurt production can harbor antibiotic resistance genes and subsequently disseminate the resistance to human beings. Monitoring antibiotic resistance in fermented foods should be a common inspection for food quality.

PERBANDINGAN BAKTERI ASAM LAKTAT YOGHURT SINGLE DAN DOUBLE STRAIN DALAM MENGHAMBAT PERTUMBUHAN Shigella dysenteriae

Dysentery is an infectious intestinal disease characterized by the appearance of blood in the stool. One of the prevention efforts is consuming fermented milk as yogurt. Yoghurt is a fermented milk using lactic acid bacteria (LAB). LAB used as single strains of Streptococcus thermophilus, Lactobacillus bulgaricus, and double strains of S. thermophilus and L. bulgaricus. The purpose of this study was to determine the ratio of LAB of single strain and double strain yoghurt in inhibiting the growth of Shigella dysenteriae by calculating the inhibition zone formed. This research used experimental design method with postest only with control group design. This study uses well diffusion. The total sample was 15, divided into 5 groups with 0%, 20%, 40%, 60%, dan 80% concentration respectively as controls. The experimental design in this study used the Completely Randomized Design (CRD) method. Data analysis used Kruskal Wallis test and Mann Whitney Post Hoc test. The results show that the average diameter of the LAB inhibition zone for double strains of S. thermophilus and L. bulgaricus > single strain L. blugaricus > S. thermophilus. In the Kruskal Wallis test, the p value was obtained = 0.002, it was found that the difference between the treated and untreated groups was obtained. The test results found a significant difference in the median inhibition zone diameter between groups. The conclusion of this study shows that the LAB double strains of S. thermophilus and L. bulgaricus are better at inhibiting growth S. dysenteriae compared to LAB single strains of L. bulgaricus or S. thermophilus yoghurt.

Nitrogen source: an effective component for the growth and viability of Lactobacillus delbrueckii subsp. bulgaricus

AbstractIn this study, we developed and optimized a growth media by evaluating various nitrogen sources for the cultivation of Lactobacillus bulgaricus, a probiotic and an important dairy starter culture. We modified the composition of deMan, Rogosa and Sharpe (MRS) culture media and substituted the nitrogen content with alternative nitrogen sources X-Seed KAT, X-Seed Carbo Max and X-Seed Nucleo Max in various blends of 5 g/l and 10 g/l respectively. Results showed that bacterial growth was significantly higher when the nitrogen source blend KCMax (10/10) was used. The optical density (OD610 nm) of the Lactobacillus bulgaricus strains were higher (1.34 and 1.79) in the KCMax (10/10) medium than in the MRS medium (0.89 and 1.42) (P < 0.05). There was no significant difference in the bacterial counts for both the MRS medium and the KCMax (10/10) medium, and all bacterial counts were estimated at 8 log CFU/ml. The buffering capacity of KCMax (10/10) was also tested and supplemented with l-histidine and was significantly different (P < 0.05) than that of the MRS control medium. Calcium supplemented in the KCMax (10/10) also served as a cryoprotectant for the cells during freezing and freeze-drying. Bacterial counts of the recovered calcium-treated freeze-dried cells were statistically significant (P < 0.05). We hypothesized that alternative nitrogen sources such as selected yeast extracts from the X-Seed brand of complex nitrogen sources could efficiently support the viability of Lb. bulgaricus. Our results thus suggested the growth of Lb. bulgaricus was efficiently supported by the X-Seed KAT, X-Seed Nucleo Max and X-Seed Carbo Max nitrogen sources. Consequently, these alternative nitrogen sources could potentially be recommended for dairy starter culture fermentations.

A novel Lactobacillus bulgaricus isolate can maintain the intestinal health, improve the growth performance and reduce the colonization of E. coli O157:H7 in broilers

ABSTRACT 1. This study aimed at the effects of a novel Lactobacillus bulgaricus (L. bulgaricus) strain and enterohemorrhagic Escherichia coli (E. coli) O157: H7 on intestinal flora and growth performance of broilers, and the protective effect of L. bulgaricus on broilers in challenged experiment by E. coli O157: H7. 2. In vitro bacteriostatic test showed that the cell-free supernatant (CFS) of L. bulgaricus isolate had an obvious inhibitory effect on E. coli O157: H7. 3. Eighty 1-day-old male broilers were randomly assigned into four treatment groups with four replicates per treatment. All groups received a basal diet in addition to the specific treatments: NC group, gavage with normal saline; In LBP group, gavage with L. bulgaricus isolate (1 × 109 CFU/mL) during the whole process and challenged with E. coli O157: H7 (3 × 109 CFU/mL); EC group, gavage with E. coli O157: H7 (3 × 109 CFU/mL); LB Group, gavage with L. bulgaricus isolate. At the age of 21 d, broilers were weighed and feed conversion ratio (FCR) was calculated. Caecum and caecal contents, ileum and faeces samples were taken after slaughter. 4. The challenge of E. coli O157: H7 resulted in an increase in TLR-4, NF-κB and IL-8 mRNA in caecal tissue, a decrease in Villus: crypt ratio in ileum, a decrease in the overall diversity of intestinal microflora and a poor FCR. 5. The L. bulgaricus isolate decreased the mRNA expression of TLR-4, NF-κB and IL-8 induced by E. coli O157: H7, reduced the content of E. coli O157: H7 in the caecum of broilers, increased the villus: crypt ratio, increased the abundance of beneficial bacteria and overall diversity of intestinal microflora, and improved FCR. 6. The L. bulgaricus isolate can maintain the intestinal health, improve the growth performance of broilers and reduce the colonisation of E. coli O157:H7 in the caecum.

Evaluation of antimicrobial activity and antibiotic susceptibility profiles of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus strains isolated from commercial yoghurt starter cultures

This research investigated the antimicrobial activity and antibiotic susceptibilities of nine Lactobacillus delbrueckii subsp. bulgaricus strains and nine Streptococcus thermophilus strains isolated from commercial yoghurt cultures. The antimicrobial activities of overnight culture strains against Bacillus cereus CECT 131, Bacillus subtilis ATCC 6633, Campylobacter jejuni NCTC 11351, Candida albicans ATCC 14053, Enterobacter aerogenes ATCC 13048, Escherichia coli ATCC 25922, Listeria monocytogenes ATCC 7644, Pseudomonas aeruginosa ATCC 9027, Salmonella typhimurium ATCC 14028 and Staphylococcus aureus ATCC 12600 were investigated using the disc diffusion method. The antibiotic resistance/susceptibility profiles of the strains were determined using antibiotic discs, which included ampicillin (10µg), ampicillin (25µg), bacitracin (10µg), clindamycin (2µg), clindamycin (10µg), erythromycin (10µg), erythromycin (15µg), gentamicin (10µg), gentamicin (120µg), nalidixic acid (30µ), neomycin (10µg), novobiocin (5µg), oxacillin (1µg), penicillin (10units), streptomycin (25µg), streptomycin (300µg), tetracycline (30µg) and vancomycin (30µg). The results of the study showed that while the Streptococcus thermophilus strain SY8, Lactobacillus bulgaricus strains LY6, LY8, LY9 and LY10 showed antimicrobial activity for all test microorganisms, Streptococcus thermophilus SY5 strains showed the weakest antimicrobial effect. All the Lactobacillus bulgaricus and Streptococcus thermophilus strains were resistant to oxacillin (1μg) and nalidixic acid (30μg). Indeed, the highest antibiotic susceptibility was seen with antibiotics such as ampicillin (25μg), clindamycin (10μg) and erythromycin (15μg).

Production and Quality Evaluation of Yogurts from Composites of Powdered Cow Milk, Soy Milk and Cornstarch

This research was carried out to evaluate the appropriate levels of substitution of powdered cow milk with soy milk and cornstarch needed to produce yoghurt, evaluating its quality and potential for acceptance. Powdered cow milk was substituted with soymilk and cornstarch up to 30% to produce yogurt and market sample yogurt was used as control. Each composite blend milk samples was homogenized, pasteurized at 75°C for 5 min, cooled and inoculated with a mixed freeze-dried starter culture containing strains of Streptococcus thermophilus and Lactobacillus bulgaricus at 45°C, fermented for 6 h and cooled to 4˚C. The proximate, chemical, microbial, functional and sensory evaluation of the composite yogurt samples was determined. The yogurt samples were coded ACS-1 to ACS-13 where ACS-13 represent control. The result of the proximate analysis showed that moisture content ranged from 82.04 – 88.71%, protein ranged 2.05 – 6.48%, fat ranged from 2.14 – 3.62%, carbohydrate ranged from 4.30 – 9.91% and ash content ranged from 0.53 – 1.48%. The pH ranged from 3.73 – 4.82. For microbial evaluation, the total viable bacteria count ranged from 1.90x107 – 11.60x107, total coliform count ranged from 0.50x107 – 3.90x107. For chemical and functional evaluation, the total solids ranged from 11.28 – 16.96%, titratable acidity ranged from 0.30 – 1.80%, syneresis ranged from 0.00 – 28.33%, water absorption capacity ranged from 0.00 – 75.53% and apparent viscosity ranged from 1337- 4863 cP. For sensory evaluation, yogurt produced with 100% powdered milk (ACS-1) was the most preferred while yogurt sample produced with 50% powdered milk, 30% cornstarch and 20% soy milk (ACS-10) was the least preferred among other yogurt samples. This study revealed the mix ratios of powdered cow milk, soy milk and cornstarch that were acceptable in accordance with yogurt standard and the extent the quality of yogurt was generally accepted with the use of processing adjuncts (soymilk and cornstarch).

Physicochemical, rheological and digestive characteristics of soy protein isolate gel induced by lactic acid bacteria

Influence of lactic acid bacteria (LAB) on gel characteristics of fermentation-induced soy protein isolate (SPI) gel, including hardness, water holding capacity (WHC), pH, solubility, turbidity, particle size, zeta potential, surface hydrophobicity, free sulfhydryl, microstructure, rheological properties and in vitro gastrointestinal digestion was evaluated. First, fermentation increased the turbidity and average particle size, which was supported by a lower degree of solubility and zeta potential absolute value. The surface hydrophobicity was reduced after lactic acid bacteria fermentation, and a similar phenomenon occurred on the free sulfhydryl groups. It was found that fermentation resulted in SPI denaturation, structural changes, and aggregates formation, which were the foundation of gel formation. Subsequently, fermentation-induced SPI gels depended on the lactic acid bacteria used for fermentation, showing the specificity of gel characteristics. Among them, Lactobacillus acidophilus (L. acidophilus), Lactobacillus plantarum (L. plantarum), Lactobacillus casei (L. casei), and mixed strains of Lactobacillus bulgaricus (L. bulgaricus), and Streptococcus thermophilus (S. thermophilus) (1:1) exhibited the high coagulation ability, which could enhance the hardness and water holding capacity of the gels. L. plantarum-G had the lowest solubility and free sulfhydryl content and the highest turbidity, particle size, and zeta potential. Scanning electron microscope (SEM) results showed that L. casei-G and L. plantarum-G exhibited a dense and uniform three-dimensional network. The rheological properties showed that the earliest gel point and the highest storage modulus (G′) and loss modulus (G″) were acquired by L. casei-G, whereas the G′ curve of L. lactis-G was still in the growth stage, and no platform was found in the growth curve. The ability of L. lactis to form gels was weaker. At the same time, the G′ and G″ of all LAB fermentation-induced gels showed strong frequency dependency. Digestion of gels was much slower than that of the soy protein isolate solution. The peptide content increased significantly during the digestion process, but, the average particle size decreased (p < 0.05). The digestion could be influenced by the microstructure of the fermentation-induced gels caused by the immobilisation of the protein in the network and the steric obstruction, including the entrance of the enzyme and release of the peptide. The current work has explored the potential of applying starters in fermented gels by performing texture, aggregation, rheological and digestive properties analysis. Our objective is to identify cultures that are suitable for developing novel functional fermentation-induced gels.

Mining of lactic acid bacteria from traditional yogurt (Mast) of Iran for possible industrial probiotic use

Lactobacillus is a genus of gram-positive bacteria of high probiotic value. The bacteria of this genus are responsible for maintaining and promoting the microbial balance of the human gut, where they along with promoting better digestion and absorption, also help in suppressing many infectious diseases. Iranian traditional yogurt (Mast) is a rich source of Lactobacillus microorganisms and their identification can be explored for their use in industrial probiotics. This study is aimed at isolation and identification of different Lactobacillus strains present in the Mast. Forty samples of Mast from eight different regions of the Iran were cultured in De Man, Rogosa and Sharpe agar (MRS) media for isolation. The isolated strains were identified by morphological and biochemical methods using gram staining, catalase, oxidase, motility and indole tests. For biochemical identification, the isolates were subjected to carbohydrate fermentation test using phenol red broth base. Overall eight strains were majorly identified based on biochemical and morphological screening which were further confirmed using 16S rDNA-based identification. Two strain of Lactobacillus acidophilus, two strains of Lactobacillus bulgaricus, two strains of Lactobacillus delbrueckii and two strains of Lactobacillus casei were identified. Lactobacillus delbrueckii subsp. Bulgaricus isolated from Bushkan showed higher bile salt resistant activities (18.92, 13.56 and 10.22%) than that of the available Lactobacillus bulgaricus strain (3.08, 1.87 and 1.44%) in 0.3, 0.5 and 1.0% bile salt. This study thus provides insights into probiotic potential of Mast which could be explored in industrial yogurt and cheese production.HighlightsInsight into Lactic Acid Bacteria profile of traditional yogurt of Iran.The Lactic Acid Bacteria profile varies from region to region.Proposes possible probiotics for commercial yogurt production from traditional yogurt of Iran.

Assessment of lactobacillus bulgaricus strain in human intestinal samples by denaturation gradient gel electrophoresis

PURPOSE. The purpose of this work was to evaluate the content of Lactobacillus bulgaricus in faecal samples of volunteers after consumption of yoghurt produced with selected L. bulgaricus strain. METHODS. Using Denaturation Gradient Gel Electrophoresis (DGGE) the DNA band corresponding to L. bulgaricus was well separated from the DNA bands of other lactobacilli. RESULTS. Faecal samples of all four volunteers consumed yoghurt contained a major DNA band indicating the presence of L. bulgaricus, unlike the faecal samples from the three volunteers no consumed yoghurt where the specific for L. bulgaricus DNA band was absent. The differences in the intensity of the electrophoretic band of L. bulgaricus are influenced by the individuality of the volunteers and the duration of yoghurt consumption. By help of DGGE it was possible to assay the presence of L. bulgaricus in faecal samples and on the base of the intensity of the specific DNA fragment to evaluate the dynamics of L. bulgaricus content during 10 days consumption of yoghurt. CONCLUSIONS. DGGE proved to be an applicable tool to monitor the presence of L. bulgaricus strains in human intestinal samples.

The Role of Probiotics in the Treatment of Dysentery: a Randomized Double-Blind Clinical Trial.

Diarrhea is considered as an important cause of morbidity and mortality, even though one of the main reasons of death following diarrhea is initiated by dysentery. In recent years, the consumption of probiotics has been proposed for the treatment of infectious diarrhea. Despite most of the studies on probiotics have focused on acute watery diarrhea, few studies in the field of dysentery have found beneficial effects of probiotics. This study is a randomized double-blind clinical trial. The patients were randomly placed into control and case groups. In the intervention group, the patients received probiotics in the form of Kidilact® sachet, which contained high amounts of 7-strain friendly bacteria strains of Lactobacillus casei, Lactobacillus acidophilus, Lactobacillus rhamnosus, Lactobacillus bulgaricus, Bifidobacterium infantis, Bifidobacterium breve, and Streptococcus thermophiles. On the other hand, the patients in the control group received placebo sachets on a daily basis for 5days. It is notable that the treatment protocol of acute dysentery was done on both groups. The results of this study showed significant differences in the duration of blood in diarrhea between probiotic consumers (2.62days) and the control group (3.16days) (P value=0.05). Additionally, significant differences in the average length of hospitalization in probiotic consumers (3.16days) and control (3.66days), (P value=0.02) could be claimed that the consumption of probiotics is effective in reducing the duration of dysentery and diarrhea. The results of this study suggest that the use of probiotics can be effective in reducing the duration of blood in diarrhea. This study was also recorded in the Iran center of clinical trials registration database (IRCT2014060617985N1).

Enhancement of Pork Jerky Using Co-cultures of Lactobacillus bulgaricus and Angel Yeast.

Strains of Lactobacillus bulgaricus and Angel Yeast were combined to ferment raw pork and make pork jerky. After fermentation, the jerky was dried and then tested for sensory evaluation, pH and free amino acid content. The results showed that the optimal conditions for fermentation using L. bulgaricus and Angel Yeast were: a pH of 6.5, a 1:1 (v/v) ratio of L. bulgaricus to Angel Yeast, a fermentation time of 42h and temperature of 25°C. The results showed that the pork jerky fermented with the combined strains was not very sour which was close to the pH of 7.0 and had a higher free amino acid content which was more than 68.3mg/100g compared with the pork jerky fermented by either L. bulgaricus or Angel Yeast alone. Overall, the results demonstrate that fermentation of raw pork with combined strains of L. bulgaricus and Angel Yeast improves the quality and flavor of pork jerky.

Structure determination of the neutral exopolysaccharide produced by Lactobacillus delbrueckii subsp. bulgaricus OLL1073R-1

The neutral exopolysaccharide (NPS) of Lactobacillus delbrueckii subsp. bulgaricus strain OLL1073R-1 was purified and characterized. The molecular mass was 5.0×106 g/mol. Sugar and absolute configuration analyses gave the following composition: d-Glc, 1; d-Gal, 1.5. The NPS was also submitted to periodate oxidation followed by borohydride reduction and Smith degradation. Sugar and methylation analyses, 1H and 13C nuclear magnetic resonance, and mass spectrometry of the NPS or of its specifically modified products allowed determining the repeating unit sequence: {2)Glc(α1–3)Glc(β1–3)[Gal(β1–4)]Gal(β1–4)Gal(α1–}n. The structure is compared to that of exopolysaccharides produced by other Lactobacillus bulgaricus strains.

Quantitative analysis of the lactic acid and acetaldehyde produced by Streptococcus thermophilus and Lactobacillus bulgaricus strains isolated from traditional Turkish yogurts using HPLC

The present study was conducted to evaluate the lactic acid– and acetaldehyde-producing abilities of lactic acid bacterial species isolated from traditionally manufactured Turkish yogurts using HPLC. The lactic acid bacterial species purified from the yogurts were the 2 most widely used species in industrial yogurt production: Streptococcus thermophilus and Lactobacillus bulgaricus. These bacteria have the ability to ferment hexose sugars homofermentatively to generate lactic acid and some carbonyl compounds, such as acetaldehyde through pyruvate metabolism. The levels of the compounds produced during fermentation influence the texture and the flavor of the yogurt and are themselves influenced by the chemical composition of the milk, processing conditions, and the metabolic activity of the starter culture. In the study, morphological, biochemical, and molecular characteristics were employed to identify the bacteria obtained from homemade yogurts produced in different regions of Turkey. A collection of 91 Strep. thermophilus and 35 L. bulgaricus strains were investigated for their lactic acid- and acetaldehyde-formation capabilities in various media such as cow milk, LM17 agar, and aerobic–anaerobic SM17 agar or de Man, Rogosa, and Sharpe agar. The amounts of the metabolites generated by each strain in all conditions were quantified by HPLC. The levels were found to vary depending on the species, the strain, and the growth conditions used. Whereas lactic acid production ranged between 0 and 77.9 mg/kg for Strep. thermophilus strains, it ranged from 0 to 103.5 mg/kg for L. bulgaricus. Correspondingly, the ability to generate acetaldehyde ranged from 0 to 105.9 mg/kg in Strep. thermophilus and from 0 to 126.9 mg/kg in L. bulgaricus. Our study constitutes the first attempt to determine characteristics of the wild strains isolated from traditional Turkish yogurts, and the approach presented here, which reveals the differences in metabolite production abilities of the wild lactic acid bacteria strains, holds the potential for the selection of the most desirable strains to be used as starters in commercial yogurt manufacture in the future.

Effect of probiotic supplementation on bacterial translocation in common bile duct obstruction.

To investigate the effects of probiotics on bacterial translocation in the obstructive common bile duct with comparison to an enteral product containing arginine and glutamine. In our study, 40 Sprague-Dawley rats each weighing 250-300g were used. Animals in Group 1 (sham) were laparatomized and fed standard chow supplemented with physiologic saline at daily doses of 2ml through orogastric tube for 7days. Common bile ducts of the animals in the other groups were ligated with 3/0 silk sutures. Group 2 (control group) was fed standard chow supplemented with daily doses of 2ml physiologic saline. Group 3 (probiotic group) was fed standard chow supplemented with a probiotic solution (Acidophilus plus) containing strains of Lactobacillus acidophilus, Bifidobacterium bifidum and Lactobacillus bulgaricus at a daily doses of 2×10(9) colony forming units (CFU). Group 4 (formula group) was fed only an enteral solution (Stresson Multi Fiber) containing glutamine, arginine and a medium-chain fatty acid at daily doses of 2g/kg. At the end of the 7th day, all animals were relaparatomized, and to determine bacterial translocation, aerobic, and anaerobic cultures were obtained from the specimens of mesenteric lymph nodes, intestinal mucosa, and blood samples. Smear cultures prepared from caecum were examined to determine the number of CFU. Finally, for histological examination specimens were excised from terminal ileum, and oxidative damage was assessed in liver tissues. Afterwards all animals were killed. Moderately lesser degrees of bacterial translocation, and mucosal damage were seen in Groups 3, and 4 relative to Group 2 (p<0.05). In Group 4, any difference was not seen in the number of cecal bacteria relative to baseline values, while in Group 3, significant decrease in cecal colonization was seen. Among all groups, a significant difference between levels of malondialdehyde, and glutathione was not observed. At the end of our study, we have concluded that both probiotics, and enteral diets which contain immunomodulators such as glutamine, and arginine alleviate bacterial translocation, and impairment of intestinal mucosa.

Lactobacillus bulgaricus - the contribution to modern healthy nutrition

Lactobacillus bulgaricus is part of the traditional Bulgarian food. It was known to the Thracians - the ancient population that lived on the territory of present Bulgaria. At the beginning of 20th century, the Russian scientist and Nobel prize winner Ilya Metchnikov, in his work "The Prolongation of Life: Optimistic Studies" relates the long and healthy life of Bulgarians to the yoghurt consumption and in particular to the local bacterium in yogurt. In the 90s of the 20th century Lactobacillus bulgaricus was used in the production of probiotic functional food for astronauts. Using modern biotechnologies, certain Bulgarian companies sheathe strains of Lactobacillus bulgaricus and other probiotic microorganisms with a natural coating, consisting of components of the growing medium during fermentation. The isolation of new probiotic strains from spring water, which normally survive under the changing climatic conditions in nature, helps the production of probiotic products in which the strains of Lactobacillus bulgaricus and other probiotic microorganisms retain their stability and vitality when passing through the gastrointestinal tract. Bulgaria becomes famous in the world for Lactobacillus bulgaricus and the Bulgarian territory is still an important reservoir for the isolation of natural strains of lactic acid bacteria which after an additional selection are used as starter cultures for the production of various fermented foods and probiotic products. Lactobacillus bulgaricus is the ancient contribution of mankind to the modern agricultural science and the creation of the first healthy foods in the world.

Identification and Partial Characterization of a Bacteriocin-Like Inhibitory Substance (BLIS) fromLb. BulgaricusK41 Isolated from Indigenous Yogurts

Forty-two strains of Lactobacillus bulgaricus isolated from locally made yogurts were examined and compared for bacteriocin producing ability using spot on lawn assay which improved by taking photo and image processing. Lb. bulgaricus K41 exhibited the highest inhibition level against indicators. K41 Bacteriocin-like inhibitory substance is sensitive to proteolytic enzymes (proteinase K, pepsin, and trypsin) but α-amylase makes slight reduction in its activity and it is resistant to lipase. This antibacterial peptide is extremely heat-stable (121 °C for 15 min) and remains active over a wide pH range (pH = 2 to 10); also nonionic detergents (Tween-20, Tween-80, and Triton X100) showed no effect on its activity. The inhibitory spectrum is against Gram-positive bacteria (except Staphylococcus aureus) with extremely antilisterial activity and it is almost ineffective against Gram-negative bacteria. The mode of its action was identified as bactericidal against Listeria monocytogenes. The properties of K41 bacteriocin-like inhibitory substance add to its safety as a biopreservative produced by a generally recognized as safe (GRAS) bacterium suggesting it can be used in hurdle technology for ready-to-eat foods as one of the main sources of Listeria contaminations.

Analysis of β-galactosidase production and their genes of two strains of Lactobacillus bulgaricus

A bacterial β-galactosidase delivery system is a potential therapy for lactose intolerance. Currently, two Lactobacillus bulgaricus strains with different biological characteristics are under consideration as potential sources. However, differences in these β-galactosidase genes and their resulting production levels are poorly characterized. The β-galactosidase ORF of L. bulgaricus yogurt isolate had high variability and was terminated at site 1924 due to a stop codon. However, the full 114 kDa β-galactosidase band was still resolved by SDS-PAGE, which may indicate that the interrupted ORF was translated into more than one peptide, and they together were folded into the complete enzyme protein that showed much higher β-galactosidase activity (6.2 U/mg protein) than the enzyme generated from L. bulgaricus reference strain (2.5 U/mg protein).

Effect of grape polyphenols on lactic acid bacteria and bifidobacteria growth: Resistance and metabolism

Food polyphenols are able to selectively modify the growth of susceptible micro-organisms. This study describes the effect of a flavan-3-ol enriched grape seed extract (GSE) on the growth of several lactic acid bacteria (LAB) and bifidobacteria and the ability of the resistant strains to metabolize these compounds. Streptococcus thermophilus, Lactobacillus fermentum, Lactobacillus acidophilus and Lactobacillus vaginalis strains showed a remarkable sensitivity to the phenolic extracts assayed, including a GSE fraction consisting mainly in (+)-catechin and (−)-epicatechin (GSE-M). On the other hand, Lactobacillus plantarum, Lactobacillus casei, and Lactobacillus bulgaricus strains reached maximal growth with the GSE fractions, including a rich-oligomeric (GSE-O) fraction. Within bifidobacteria, Bifidobacterium lactis BB12 showed the highest sensitivity to the phenolic extracts assayed, whereas Bifidobacterium breve 26M2 and Bifidobacterium bifidum HDD541 reached maximum growth in presence of GSE-O and GSE-M fractions. Metabolism of flavan-3-ols by LAB and bifidobacteria resistant strains was investigated in vitro. The results revealed that only L. plantarum IFPL935 was able to metabolize the polyphenols studied by means of galloyl-esterase, decarboxylase and benzyl alcohol dehydrogenase activities that led to the formation of gallic acid, pyrogallol and catechol, respectively. An unknown metabolite that does not exhibit a phenolic-acid-type structure was also detected, which suggests a new enzyme activity in L. plantarum IFPL935 able to degrade flavan-3-ol monomers.

Analyzing and monitoring of phage–bacteria interaction using CE

The utilization of CE for monitoring bacteria-phage interaction was investigated in this study. Streptococcus thermophilus and Lactobacillus bulgaricus strains and their phages were used as model bacteria and phages for the purpose of validation in this study. CE with heterogeneous polymer polyethylene oxide was utilized for the separation of intact bacteria and investigation of phage-bacteria interaction. An intact phage detection was carried out with CZE by adding SDS in the running buffer. Calibration graphs of bacteria and phages were obtained with R(2) values of 0.963 and 0.937, respectively. S. thermophilus strain was infected with its virulent phage B3-X18 for investigation of phage-bacteria interaction. It was observed in capillary electropherogram that the culture was lysed depending on the multiplicity of infection value and it showed to be completely lysed when the multiplicity of infection value was 10. The interaction of S. thermophilus strain with L. bulgaricus phage was also investigated by using a CE and a microbiological method and it was observed that the L. bulgaricus phage attached itself to the cell wall of S. thermophilus strain without damaging the cell.

Non-Fusion and Fusion Expression of β-Galactosidase from Lactobacillus bulgaricus in Lactococcus lactis

To construct four recombinant Lactococcus lactis strains exhibiting high beta-galactosidase activity in fusion or non-fusion ways, and to study the influence factors for their protein expression and secretion. The gene fragments encoding beta-galactosidase from two strains of Lactobacillus bulgaricus, wch9901 isolated from yogurt and 1.1480 purchased from the Chinese Academy of Sciences, were amplified and inserted into lactococcal expression vector pMG36e. For fusion expression, the open reading frame of the beta-galactosidase gene was amplified, while for non-fusion expression, the open reading frame of the beta-galactosidase gene was amplified with its native Shine-Dalgarno sequence upstream. The start codon of the beta-galactosidase gene partially overlapped with the stop codon of vector origin open reading frame. Then, the recombinant plasmids were transformed into Escherichia coli DH5 alpha and Lactococcus lactis subsp. lactis MG1363 and confirmed by determining beta-galactosidase activities. The non-fusion expression plasmids showed a significantly higher beta-galactosidase activity in transformed strains than the fusion expression plasmids. The highest enzyme activity was observed in Lactococcus lactis transformed with the non-fusion expression plasmids which were inserted into the beta-galactosidase gene from Lactobacillus bulgaricus wch9901. The beta-galactosidase activity was 2.75 times as high as that of the native counterpart. In addition, beta-galactosidase expressed by recombinant plasmids in Lactococcus lactis could be secreted into the culture medium. The highest secretion rate (27.1%) was observed when the culture medium contained 20 g/L of lactose. Different properties of the native bacteria may have some effects on the protein expression of recombinant plasmids. Non-fusion expression shows a higher enzyme activity in host bacteria. There may be a host-related weak secretion signal peptide gene within the structure gene of Lb. bulgaricus beta-galactosidase, and its translation product may introduce the enzyme secretion out of cells in special hosts.