- Complete DNA Sequence of Lactococcus lactis Adds Flavor to Genomics
- Lactococcus lactis
- Probiotic effect of feeding Lactococcus lactis and Streptococcus thermophilus on periodontitis induced rat model
- Animals and induction of experimental periodontitis
- Analysis of micro-computed tomography
- Bacterial count with real-time polymerase chain reaction
- Enzyme-linked immunosorbent assay
- Statistical analysis
- Protective effects of a novel probiotic strain, Lactococcus lactis ML2018, in colitis: in vivo and in vitro evidence – Food & Function (RSC Publishing)
- Yogurt and other fermented foods as sources of health-promoting bacteria
- FERMENTATION-ASSOCIATED MICROBES AND THEIR JOURNEY TO THE GUT
- Lactococcus lactis: Health benefits
- Antibiotic properties
- Boosting your immune system
Complete DNA Sequence of Lactococcus lactis Adds Flavor to Genomics
- Molecular Genetics Group, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9750 AA Haren, The Netherlands
With the publication of the long-awaited genome sequence ofLactococcus lactis ssp. lactis IL1403, Bolotin et al. (2001) have set the stage for functional and comparative genomics of an important group of industrial microorganisms, that is, the lactic acid bacteria (LAB).
LAB are widely used for starting industrial fermentations of milk, vegetables, meat, and fish. L. lactisis used in cheesemaking, as it is involved in casein degradation, in acidification by formation of lactate, and in the formation of flavor compounds.
Other LAB, such as Streptococcus thermophilus,Lactobacillus delbrueckii subsp. bulgaricus, and certain Bifidobacteria, are used for yogurt production, whereas Proprionibacteria and other species contribute to the product characteristics of Swiss-type cheeses. L.
lactis is the major starter for Cheddar production; for a Dutch cheese such as Gouda, a complex starter culture containing >100 different strains of LAB is used.
L. lactis is by far the best characterized LAB with respect to its physiology, metabolic pathways, and regulatory mechanisms. The ease of genetic modification of various species of LAB and the existence of a worldwide network of LAB researchers have greatly stimulated fundamental and applied research in LAB (Gasson and de Vos 1994; Konings et al. 1999).
Industrial applications are directed mainly toward improvement of flavor, texture, and preservation characteristics of fermented products as well as enhancement of industrial robustness of starter cultures. Novel uses of LAB, such as in oral vaccines or in preparation of functional foods or their direct application as a probiotic culture, are also being explored (Delcour et al. 1999).
For oral vaccines, specific antigenic determinants are overproduced either intra- or extracellularly in LAB and subsequently administered orally, nasally, or vaginally to the animal to stimulate mucosal immunity (Gilbert et al. 2000). In situ production of interleukin in mice has already been successful, showing the high potential of LAB for medical applications (Steidler et al. 2000).
The main breakthroughs for using L. lactis as an improved cell factory were the development of a wide variety of genetic modification tools, highly effective controlled-gene expression systems, novel metabolic engineering strategies, and food-grade cloning systems (Kuipers et al. 2000).
In this respect, all requirements are fulfilled to make optimal use of the information to be mined from the lactococcal genome.
The investigators from INRA and Génoscope have used an original approach, comprising diagnostic sequencing followed by a shotgun polishing step. This has resulted in a 2.37-Mb genome sequence, which upon annotation revealed 2310 proteins. The error rate in the final sequence is stated to be
- What is Lactococcus lactis?
Lactococcus lactis is known as a bacterium that’s Gram-positive. It is used in the industry for the production of cheese and buttermilk. Lately, it was utilized as a genetically modified organism for treating various diseases. It’s the first alive organism used for this purpose. http://www.descargarjuego.org/125-rust-download.html
If the bacterium is put into milk, it breaks down the lactose into energy molecules, ATP, with the help of various enzymes. The ATP’s byproduct is called lactic acid. This one is useful for coagulating the milk and then forming the curds that produce whey and cheese.
Moreover, Lactococcus lactis can be utilized for preparing fermented foods sausages, breads, wine, beer and pickled vegetables. Many specialists stated that understanding and using the genetic and physiology functions of this bacterium would be extremely valuable for the pharmaceutical and food industries. The bacterium could be used to produce many beneficial drugs as well.
Lactococcus lactis, commonly known as L. lactis, can be found in the gastrointestinal tract, the hair and the skin of animals and on various plant surfaces. On the plant, L. lactis has an inactive form. The multiplying process begins when the bacterium enters the gastrointestinal tract of the animal.
L. lactis is mainly used by the dairy industry in order to ferment the cheese. The soft cheeses usually have this bacterium as a primary ingredient.
Many people all around the world ingest these bacteria when consuming cheese. Reports say that cheese is produced annually in a quantity of more than 10 million tons.
As mentioned before, it’s also useful for producing pickled vegetables, wine and beer.
Recently, Lactococcus lactis entered the biomedical area. It was soon discovered that the bacterium can be a delivery vector for the immune modulatory and therapeutic proteins and also for antigens.
Animal and in vitro studies confirmed this beneficial fact. Further tests proved that the interleukin which contains L. lactis can treat and prevent the IBD or the inflammatory bowel disease. Thus, the medical use of L.
lactis that’s genetically modified might evolve in the upcoming years.
The Lactococcus lactis has a safety profile. Therefore, it can be seen as a safe delivery vector. Moreover, the bacterium is non-commensal and non-invasive.
It doesn’t colonize the bowel and the colon and doesn’t have any side effects or immunotolerance if it’s used for a long time. Other specialists discovered that the L.
lactis is very much a other delivery systems, the microparticle vaccines. These reach the intestinal mucosa, where the microfold cells take them up.
For centuries, people consumed the L. lactis bacterium by ingesting various fermented foods. This is the safest way to take this bacterium and benefit from its properties. In order to produce various proteins, the L. lactis is genetically engineered.
Many studies were conducted so as to observe this particular feature. Most of them tried to see if the genetically engineered bacterium can generate vectors able to protect the mucosal tissues with therapeutic proteins. One specific trial had shown that the L.
lactis can produce interleukin-10, that’s helpful for Crohn’s disease.
Probiotic effect of feeding Lactococcus lactis and Streptococcus thermophilus on periodontitis induced rat model
P. gingivalis ATCC 33277 was used for induction of periodontitis and cultured with brain heart infusion (BHI) broth (BD Biosciences, San Jose, CA, USA) supplemented with hemin (1 μg/mL) and vitamin K (0.
2 μg/mL) at 37°C in an anaerobic condition (5% H2, 10% CO2, and 85% N2). Also, L. lactis HY 449 and S. thermophilus HY 9012 were gratefully donated from Yakult (Korea Yakult Co.
, Yongin, Korea) and cultivated with BHI broth at 37°C, anaerobically.
Animals and induction of experimental periodontitis
Male Wistar rats (250–300 g) were purchased from ORIENT Co. (Seongnam, Korea) and used to induction of periodontitis. Also, all experiments using rat were carried out in separate space with facilities for animal experiments.
The rats were allowed food and water ad libitum and were maintained on a 12 hours light and dark cycle at 24°C with 50% to 60% humidity for 1 week before use. Also, all animals were maintained by according to the guidelines of laboratory animal ethics committee in Dankook University.
The rats were anesthetized with isoflurane gas and the sterile 4-0 (diameter, 0.4 mm) braided silk (Perma-hand silk; Ethicon, Somerville, NJ, USA) was placed around the cervix of the lower second molars and knotted medially. The rats were randomly allocated into five groups with 5 rats per group.
Control group was not ligated with the silk and the others were ligated with P. gingivalis inoculated silk. The grouping of experimental rats was described in more detail in Table 1. In order to induce periodontitis, P.
gingivalis suspension (100 μL, 1×109 colony-forming unit [CFU]/mL) was inoculated into the knotted silk, and the rats were bred for 20 days. Control group (10 rats) was fed the regular diet, and the experimental groups (15 rats per group) were fed the diet containing L. lactis, S. thermophilus, or both probiotics (1×107 CFU/g).
The diets with mixture regular food and probiotics were made by Korean Yakurt. After displacing the ligatures, gingival crevicular fluid (GCF) and bacteria in subgingiva were collected with four paper points (#40, taper size 0.04 mm). Two paper points were used for enzyme-linked immunosorbent assay (ELISA) analysis to investigate inflammatory cytokines, and the remaining paper points were used for bacterial count.
Groups of experimental rats
|Control||None-ligature and regular diet|
|Regular diet||Ligature and regular diet|
|Streptococcus thermophilus diet||Ligature and diet containing S. thermophilus|
|Lactococcus lactis diet||Ligature and diet containing L. lactis|
|S. thermophilus+L. lactis diet||Ligature and diet containing S. thermophilus+L. lactis|
Analysis of micro-computed tomography
Mandible was subjected by micro-computed tomography (CT) using an X-ray micro-CT scanner (SkyScan 1172; SkyScan Co., Kontich, Belgium) after collection at end time point of the experiment.
The image intensifier to obtain two-dimensional images of each level, the scanning was performed under the condition of 80 keV, 100 μA, and 16.8 magnification with the spot size of 8 μm. The level of alveolar bone resorption was analyzed according to the method by Park et al. .
Briefly, linear measurements were taken from the cementoenamel junction to the root apex line in the interdental region between the first and second molars. The ratio of remaining alveolar bone between first and second molar in the left mandible was compared among each group.
The three-dimension (3D) area of alveolar bone was measured by program under development which can calculate 3D area from 3D image of micro-CT data and confocal laser microscopy data.
Bacterial count with real-time polymerase chain reaction
For count of P. gingivalis or probiotics in subgingiva of the ligature site of the rats, quantitative real-time polymerase chain reaction (PCR) was performed using specific primer of each bacterium. First, the standard curve was generated using from various bacterial count (1×103 to 1×107) and Cycle threshold (Ct) of amplified DNA of each bacterium.
Each bacterial DNA was extracted from various amount of the bacteria by G-spin Genomic DNA extraction kit (iNtRON Biotech., Seongnam, Korea) after counting the bacteria with bacterial counting chamber (Marienfeld-Superior, Lauda-Königshofen, Germany). DNA was mixed with TB Green premix Ex Taq GC (Takara Bio Inc., Kyoto, Japan), 0.4 μM of each primer pair in 20 μL final volume.
The mixture was carried out real-time PCR with ABI prism 7500 real-time PCR system (Applied Biosystems, Foster City, CA, USA). The condition of the PCR was 40 cycles at denaturing 94°C for 10 seconds, annealing at 60°C for 10 seconds, and extension at 72°C for 33 seconds.
The sequence of the used primers was as follows: 5’-CTC GTG GTC ACA AGC AGT AG-3’ and 5’-GGA ATG ACG GTT TCA ATC GTG-3’ for L. lactis gene; 3’-TCA CTA TGC TCA GAA TAC AAA TC-3’ and 5’-ACC CAT ACA AAG ATG GAA GTAG-5’ for S. thermophilus gene; 5’-TGC AAC TTG CCT TAC AGA GGG-3’ and 5’-ACT CGT ATC GCC CGT TAT TC-3’ for P. gingivalis gene.
The bacterial level was calculated using Ct level from the standard curve. The PCR products were investigated for each specific amplification product using a dissociation curve of amplification.
Enzyme-linked immunosorbent assay
The collected GCF using paper point from the rat were eluted by Dulbecco’s phosphate-buffered saline to investigate inflammatory cytokines, and the levels of interleukin (IL)-1β and tumor necrosis factor (TNF)-α was measured by ELISA kit (BD Biosciences) according to manufacturer’s protocol.
All results were expressed as mean±standard deviation and analyzed by Kruskal–Wallis non-parametric analysis and Mann–Whitney non-parametric analysis using SPSS ver. 24 (IBM Corp., Armonk, NY, USA). p-value less than 0.05 were considered statistically significant.
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Protective effects of a novel probiotic strain, Lactococcus lactis ML2018, in colitis: in vivo and in vitro evidence – Food & Function (RSC Publishing)
* Corresponding authors
a Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education and Tianjin, College of Biotechnology, Tianjin University of Science and Technology, P.R. China
Fax: +086 2260 602 298
Tel: +086 2260 602099
Multiple articles have confirmed that an imbalance of the intestinal microbiota is closely related to aberrant immune responses of the intestines and to the pathogenesis of inflammatory bowel diseases (IBDs). Probiotic strains have been identified for the treatment and prevention of IBDs.
The aim of this study was to screen a new probiotic strain with anti-inflammatory activity and investigate the potential mechanisms underlying its activity. We identified a new probiotic strain, L. lactis ML2018, that has anti-inflammatory properties and was isolated from traditional fermented food. In an in vitro experiment, L.
lactis ML2018 prevented the release of nitric oxide (NO) and the production of inflammatory factors induced by lipopolysaccharides (LPS) in RAW264.7 cells. The in vivo anti-inflammatory effects of L. lactis ML2018 were evaluated using a dextran sulfate sodium (DSS)-induced animal model of colitis. Oral administration of L.
lactis ML2018 significantly ameliorated colitis induced by DSS, which included preventing a decrease in body weight, shortening of the colon length and apoptosis of epithelial cells. L.
lactis ML2018 could inhibit DSS-induced intestinal inflammation by preventing the overproduction of proinflammatory factors, suppressing the infiltration of macrophages, controlling the fibrosis, improving the integrity of the intestinal epithelial barrier and upregulating the concentrations of short-chain fatty acids (SCFAs).
Moreover, L. lactis ML2018 could prevent inflammation by inhibiting the activation of the NF-κB and MAPK signaling pathways. These data suggest that L. lactis ML2018 could have therapeutic potential for treating IBDs.
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Back to tab navigation https://doi.org/10.1039/C8FO02301H Food Funct., 2019,10, 1132-1145
M. Liu, X. Zhang, Y. Hao, J. Ding, J. Shen, Z. Xue, W. Qi, Z. Li, Y. Song, T. Zhang and N. Wang, Food Funct.
, 2019, 10, 1132
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Yogurt and other fermented foods as sources of health-promoting bacteria
Increased consumption of yogurt, kefir, and other fermented foods has been driven, in part, by the health benefits these products may confer. Epidemiological studies have shown that the consumption of fermented foods is associated with reduced risks of type 2 diabetes, metabolic syndrome, and heart disease, along with improved weight management.
The microorganisms present in these foods are suggested to contribute to these health benefits. Among these are the yogurt starter culture organisms Streptococcus thermophilus and Lactobacillus delbrueckii subsp bulgaricus as well as Bifidobacterium and Lactobacillus strains that are added for their probiotic properties.
In contrast, for other fermented foods, such as sauerkraut, kimchi, and miso, fermentation is initiated by autochthonous microbes present in the raw material. In both cases, for these fermentation-associated microbes to influence the gut microbiome and contribute to host health, they must overcome, at least transiently, colonization resistance and other host defense factors.
Culture and culture-independent methods have now clearly established that many of these microbes present in fermented dairy and nondairy foods do reach the gastrointestinal tract.
Several studies have shown that consumption of yogurt and other fermented foods may improve intestinal and extraintestinal health and might be useful in improving lactose malabsorption, treating infectious diarrhea, reducing the duration and incidence of respiratory infections, and enhancing immune and anti-inflammatory responses.
For thousands of years, fermented foods have been a major part of the human diet,1 largely because fermented milk, meat, and plant foods could be better preserved than the fresh raw materials from which they were made.
2 In the absence of drying, salting, or other forms of traditional preservation, perishable foods would spoil or become unsafe to consume.
Most fermented foods, in contrast, naturally contain organic acids, ethanol, or other antimicrobial compounds that inhibit the growth of spoilage organisms and foodborne pathogens.
In addition to their enhanced preservation qualities, fermented foods have other attributes that account for their popularity, including unique flavors, textures, and appearances as well as added functionality and economic value.
In many parts of the world, fermented foods are among the most important sources of nutrients.3–5 Cultured dairy products, bread, and fermented sausage, for example, are rich sources of protein, minerals, and vitamins.
Fermentation may also reduce the concentration of lactose and other fermentable sugars and increase phenolic compounds that provide antioxidant activity.
6,7 Importantly, there is emerging epidemiological and clinical evidence to suggest that the microorganisms responsible for fermentation, along with those added to fermented foods in the form of probiotics, may contribute directly to gastrointestinal and systemic health.8
The microorganisms that are predominantly involved in the manufacture of fermented dairy, meat, and vegetable products are lactic acid bacteria from the genera Lactobacillus, Streptococcus, Pediococcus, and Leuconostoc.
Other bacteria, including acetic acid bacteria, are also important in the fermentation of cocoa beans, vinegar, and kombucha.
9,10,Saccharomyces cerevisiae and other yeasts are widely used in beer, wine, and bread manufacture, and Penicillium spp, Aspergillus spp, and other fungi are used in cheese, fermented meats, and soy-fermented foods. For many foods, bacteria and yeast are combined to produce the desired product.11,12
Although microorganisms are required for the production of the foods mentioned above, not all fermented foods contain live microbes at the time of consumption.
For example, lactic acid bacteria and yeast are used in sourdough bread fermentation, but after baking, none of these organisms are present in the finished bread.
Similarly, the organisms responsible for wine and beer fermentation are inactivated or physically removed and are absent from the finished product. Nonetheless, vitamins and bioactive molecules produced by the microbes may still be present.
In addition, microbes also consume or transform food constituents during fermentation, resulting in compositional changes in the food. However, even in the absence of a heat or separation step, the number of microbes present at the time of consumption depends on the composition, the storage conditions, and the age of the food.13,14
Understanding the molecular basis for the manner in which fermented foods and fermentation-associated microorganisms affect human health has been challenging.
However, next-generation sequencing and other molecular methods are now routinely used to identify and assess abundances of microbes present in fermented foods as well as within gastrointestinal microbiomes.15,16 Thus, it is now possible to track specific strains present in fermented foods from consumption to the gastrointestinal tract.
17–19 Transcriptomics, metabolomics, and whole-metagenome sequencing are also being used to identify or predict functional traits of fermentation-associated microorganisms.20–22
The goal of this review was to assess the nutritional role of live microbes present in fermented foods, with an emphasis on yogurt and other cultured dairy products.
The physiological and ecological challenges faced by fermentation-associated and food-related microbes during digestion and transit through the gastrointestinal tract will be described first. Evidence showing that many of these organisms do indeed survive transit will follow.
The ability of food-associated microbes to influence the composition of the intestinal microbiota and ameliorate gut imbalances or dysbiosis will be described next. Finally, the health benefits of fermented foods, as reported in epidemiological and clinical studies, will be reviewed.
In particular, improved lactose digestion by yogurt bacteria—currently the only approved health claim for a fermented food—will be described.
FERMENTATION-ASSOCIATED MICROBES AND THEIR JOURNEY TO THE GUT
For food-associated microorganisms to directly influence the intestinal microbiota and improve the nutritional status of the host, they must first traverse several early hurdles23 (Figure 1).
In the mouth, saliva contains enzymes and other antimicrobial constituents, and the oral microbiota itself provides colonization resistance.24,25 In the stomach, gastric pH is usually less than 3.0 (depending on the fasting state), and pepsin, trypsin, and other digestive enzymes effectively degrade cell proteins.
23 Bile salts secreted into the small intestine disrupt cell membranes and contribute to cell permeabilization and death.26
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Challenges faced by food-associated microbes during their transit through the alimentary canal. The presence of proteases, lipases, and other digestive enzymes are initially responsible for the degradation of cell proteins and lipids.
The change in pH along the digestive tract also acts as an additional barrier for these microbes. The pH is lowest in the stomach, owing partly to the secretion of hydrochloric acid by the gastric mucosa, and this can be especially detrimental to non–acid-tolerant microbes.
Even if these microbes can successfully survive gastric challenges, bile acids are produced by the host in the small intestine, and the residential microbes present in the gastrointestinal tract release short-chain fatty acids.
With all these hurdles in place, it is perhaps surprising that so many of these food-associated microbes are still able to survive transit into the colon. Abbreviation: SCFA, small-chain fatty acids.
Despite these challenges, evidence both culture and culture-independent methods shows that many of the organisms present in a wide range of fermented foods do indeed survive transit through the gastrointestinal tract. (Table 1)18,27–38.
For example, using culture-based methods, Streptococcus thermophilus and Lactobacillus delbrueckii subsp bulgaricus were detected in duodenum samples from intubated subjects within 15 minutes after fresh yogurt had been consumed.
32 In ileal perfusion experiments in human participants, the same researchers also showed that more than 20% of a strain of Bifidobacterium sp consumed in milk reached the ileum.28 wise, recovery rates of Lactobacillus casei DN-114 001 and Lactobacillus plantarum NCIMB 8826 consumed in fermented milk were above 50% and at 7%, respectively, in ileal samples.
29,30 In contrast, survival rates of other lactic acid bacteria (including strains of Lactococcus lactis and Lactobacillus fermentum) recovered from the ileum were 1% or less.30
Detection and recovery of fermentation-associated microbes after ingestion
|David et al (2014)27||Cheese & cured meat||–||Animal-based diet consisting of cheese and cured meats for dinner||Stool||Increase in Lactococcus lactis, Pediococcus acidilactici, and Staphylococcus spp||Molecular: 16S rRNA|
|Increase in Penicillium-related fungi. Decrease in Debaryomyces spp and Candida spp||Molecular: ITS|
|Pochart et al (1992)28||Fermented milk||Bifidus milk containing Bifidobacterium sp strain BB||2.5 × 107 CFU/g||Ileal fluid||23.5% ± 10.4% survivala||Culture: plate count on TPY + 0.5% propionic acid|
|Oozeer et al (2006)29||Fermented milk||Lactobacillus casei DN-114 001||108 CFU/mL||Ileal fluid||3.6% ± 1.8% survivala||Culture: plate count on MRS agar + rifampin (100 ug/mL)|
|Stool||7.6 log10 CFU/g|
|Vesa et al (2000)30||Fermented milk||Lactobacillus fermentum KLD||1.0 × 107 CFU/g||Ileal fluid||0.5% ± 0.5% survivala||Culture: plate count on MRS agar + rifampin (50 ug/mL) + streptomycin (200 ug/mL)|
|Lactobacillus plantarum NCIMB 8826||7.6 × 108 CFU/g||Ileal fluid||7.0% ± 2.0% survivala|
|Stool||25% ± 29% survivala|
|Lactococcus lactis MG 1363||3.0 × 107 CFU/g||Ileal fluid||1.0% ± 0.8% survivala|
|Veiga et al (2014)18||Fermented milk||Bifidobacterium animalis subsp lactis CNCM I-2494||1.25 × 1010 CFU/serving||Stool||Increase in all 4 species in the fermented milk, Clostridiales and Bifidobacterium dentium. Decrease in Bilophila wadsworthia, Parabacteroides distasonis, and Clostridium sp HGF_2||Molecular: whole genome sequencing|
|Streptococcus thermophilus CNCM I-1630||1.25 × 109 CFU/serving|
|Lactobacillus delbrueckii subsp bulgaricus CNCM I-1632 and CNCM I-1519||1.25 × 109 CFU/serving|
|Lactococcus lactis CNCM I-1631||1.25 × 109 CFU/serving|
|Shibahara-Sone et al (2016)31||Fermented milk||Bifidobacterium bifidum YIT 10347||≥ 109 CFU/100 mL||Gastric body biopsy||Detected in all individualsb||Molecular: RT-qPCR|
|Pochart et al (1989)32||Fresh yogurt||Lactobacillus bulgaricus strain S85||1.26 × 108 CFU/g||Duodenal||1.99 × 102 CFU/gc||Culture: plate count on MRS agar|
|Streptococcus thermophilus strain S85||5.01 × 108 CFU/g||1.58 × 103 CFU/gc||Culture: plate count on M17 agar|
|del Campo et al (2005)33||Fresh yogurt||Streptococcus thermophilus||2 × 108 CFU/g||Stool||Detected in 8.4% of total individuals||Molecular: DNA hybridization|
|Lactobacillus delbrueckii||1.3 × 107 CFU/g||Detected in 3.15% of total individuals|
|Streptococcus thermophilus||2 × 108 CFU/g||Not detected||Culture: isolation on MRS and M17 agars|
|Lactobacillus delbrueckii||1.3 × 107 CFU/g||Not detected|
|Mater et al (2005)34||Yogurt||Streptococcus thermophilus||7.8 × 108 CFU/mL||Stool||6.3 × 104 CFU/g||Culture: plate count on M17 agar + streptomycin (1 µg/mL) + rifampin (100 µg/mL)|
|Lactobacillus delbrueckii subsp bulgaricus||7.5 × 108 CFU/mL||7.2 × 104 CFU/g||Culture: plate count on MRS agar + streptomycin (1 µg/mL) + rifampin (100 µg/mL)|
|Elli et al (2006)35||Yogurt||Streptococcus thermophilus||5 × 1010 CFU/serving||Stool||Detected in 5% of total individuals||Culture: plate count on RSM + 0.05% ruthenium red dye|
|Lactobacillus delbrueckii subsp bulgaricus||6 × 109 CFU/serving||Detected in 65% of total individuals|
|Kil et al (2004)36||Kimchi||Lactobacillus sp||60 g to 300 g of kimchi||Stool||3.5 – 6 log CFU/mLd||Culture: plate count on modified LBS medium|
|Leuconostoc sp||4 – 6.5 log CFU/mLd||Culture: plate count on PES|
|Lee et al (1996)37||Kimchi||Lactobacillus sp||200 g of kimchi||Stool||6.87 ± 1.05 log CFU/g||Culture: plate count on MRS agar + bromophenol blue|
Lactococcus lactis: Health benefits
many probiotic strains, Lactococcus lactis has been used for hundreds of years to ferment foods such as cheese, yoghurt, sauerkraut.
It works by fermenting milk sugar (lactose) into lactic acid, which makes it a useful tool in the cheese-making industry.
Lactococci are non motile, non-spore forming bacterium that are usually associated with plant material (mostly grasses). This bacterium is easily inoculated into milk.
Although Lactococcus lactis is related to other lactic acid bacteria (such as Lactobacillus acidophilus) that colonize the intestines and mouth, L. lactis doesn’t usually colonize human tissues. It also differs from other lactic acid bacteria in terms of its pH, salt, and temperature tolerances for growth.
Besides the production of fermented dairy products, Lactococcus lactis is now being utlitized for biotechnological applications in genetic engineering for the production of various recombinant proteins and metabolites, particulary in vaccine delivery systems. In recent years, scientists have developed a means of using L. lactis for nisin-controlled gene expression (NICE).
However, Lactococcus has one very important feature: it’s a component of nisin, an antibiotic- substance that fights a wide variety of Gram-positive bacteria. This includes food-borne pathogens such as Listeria, Staphylococcus and Clostridium. Research suggest that nisin targets the cell membrane of these bacteria.
Nisin is a natural preservative present in cheese made with Lactococcus lactis ssp. lactis, but can also be used as a preservative in foods with low pH. Because nisin cannot be synthesized chemically, Lactococcus lactis strains are commonly used for this purpose.
Boosting your immune system
For humans, the most important use of Lactococcus lactis is in boosting the immune system. L.
lactis has been shown to be particularly effective in delivering antigens that stimulate mucosal immunity to pathogens of the respiratory tract.
It also appears to to exhibit protection against nonrespiratory pathogens, such as HIV, Human papilloma virus and the malarial parasite.
lactis can survive the harsh conditions of the gastrointestinal tract but doesn’t colonize the gut ( other Lactobacillus strains), it can be used as a “vehicle” to deliver therapeutics such as cytokines into the human body. This was first done in a study involving mice with colitis, where engineered secretion of interleukin-10 (IL-10) in L. lactis was used to treat inflammatory bowel disease.
A Japanese study has also found health benefits for Lactoccocus lactis. By using the bacteria Salmonella Flagellar, researchers were able to use L.
lactis to produce acetate (through lactose fermentation) and subsequently interrupt the rotation of the bacteria’s flagella – thus hindering the ability of the Salmonella to move through the body. It was concluded that Lac.
lactis may be a useful tool for preventing infections by multiple bacterial species.
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