Lactobacillus[11]）It is the general name of various bacteria that can decompose glucose and other sugars into lactic acid.[1]Lactobacillus is a kind of non spore bacillus, belonging toGram positive bacteria。Single, double or short chain arrangement;Anaerobic respiration.[2]Lactobacillus has strong metabolismcarbohydrateAcid producing ability, which can synthesize glucan and heteropolysaccharide.[3]It can ferment sugar to produce lactic acid or other acids.The lactic acid produced has the functions of seasoning and antisepsis.[2]
Widely distributed in nature, some strains are one of the normal flora of human and animal oral cavity, intestinal tract and vagina, rarely cause disease, and are basically harmless to human except for subacute bacterial endocarditis.Lactobacillus parasitized in oral cavity plays an important role in caries.It is generally believed that lactobacilli parasitic in the intestines and vagina can protect the body. Some lactobacilli, such as Lactobacillus acidophilusLactobacillus bulgaricus, commonly used in beverage fermentation industry.[4]
Has been removed from animal fecesVaginal discharge, cheese, sauerkraut, etc.They can antagonize pathogenic bacteria and help maintain the body's cells andHumoral immune response。[5]All lactobacilli are widely used in pickling pickles, making yogurt, silage and other processing industries.[2]
gram-positiveBacillus, long picea, short picea, sometimes rod-shaped, slender, but unbranched.No spore.The colony is round, white (sometimes yellow), translucent, smooth and convex, with neat edges. The rough surface is dull, and the edges are uneven.[3]
Physical and chemical properties
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There are two types of fermentation: homogeneous fermentation (producing lactic acid) and heterogeneous fermentation (producing lactic acid, acetic acid, formic acid and succinic acid).[3]It is acid resistant and generally propagates under anaerobic conditions.The suitable temperature is about 5 ℃.[1]
Acetyl, the metabolite of Lactobacillus, is a special flavor substance of dairy products such as butter and cheese, which has inhibitory effects on many putrefactive bacteria and pathogenic bacteria.It is reported that diacetyl can beGram negative bacteriaArginineBinding proteinTo interfere with the utilization of arginine and inhibit the growth of gram-negative bacteria.[1]
Culture characteristics
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The optimum pH value for growth is 4-6.[5]Acid resistant growth can still grow in pH3.8 environment.[3]The strain does not produce gas and can grow at 20 ℃.[1]
When separating lactobacilli from different samples, different components of culture media can be selected according to the different habitats of lactobacilli and whether they are dominant bacteria.Common media include MRS (Man Rogosa Sharpe), RSMA (Ruthenium Skim Milk Agar), Tomato Juice Agar, etc.The colony morphology of common lactobacilli on MRS medium: Lactobacillus curlicus: full in the middle, diffuse around, irregular;Lactobacillus johnsonii: plump, regular edge;Lactobacillus griffii: flat, diffuse around, regular edge.[6]
Distribution area
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Lactobacillus is widely distributed in the surrounding environment, especially in the digestive tract and vagina of animals.[6]
bygram-positiveBacillus, usually arranged in a chain, has no power, does not form spores, is slightly aerobic or anaerobic, has strict nutritional requirements, and is difficult to cultivate.It is commonly found in milk, dairy products, meat products, beer, wine, fruit and juice, pickles and wort.It also parasitizes in the mouth, intestines and vagina of humans and animals.Very few are pathogenic.[7]
Representative strain
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There are 15 kinds of bacteria that can be separated in the mouth, including:Lactobacillus casei（L.caei）: subspecies including cheese subspecies（L.casei subst）, paracheese subspecies（L. paracasei subs）、Lactobacillus acidophilus（L.acidophilus）。The subspecies are: eosinophil subspecies（L.acidophilus subsp）, Curly subspecies（L.crispatus）Other strainsLactobacillus fermentans（L.ferments）、Lactobacillus salivarius（L.salivarius）、Lactobacillus plantarum（L.plantarum）、Lactobacillus brevis(L.brevis), Lactobacillus brucei（L.buchneri）, Lactobacillus goethii（L.gassert）, Lactobacillus oral（L.orzs）、Lactobacillus rhamnosus（L.rhamnosus）, Lactobacillus gingivalis（L.uli）, Lactobacillus zeae（L.zeae）[3]Three kinds of lactobacillus were found in human excreta: Lactobacillus acidophilus, Lactobacillus fermentans and Lactobacillus salivarius.[8]
Lactobacillus casei （L.casei）, Lactobacillus bulgaricus（L.bulgaricus），Lactobacillus acidophilus（L.acidophilus）, Lactobacillus thermophilus（L.thermophilus）Etc.These bacteria are often used as fermentation bacteria for the production of lactic acid, cheese, yogurt and other dairy products.[7]
Lactobacillus bulgaricus
Lactobacillus bulgaricus
Lactobacillus bulgaricus is a large bacterium with a size of about 0.8-1 × 2-20μm. Single or chained, Gram staining is positive, metachromatic particles can be seen in methylene blue staining bacteria, no movement, no spores.
This bacterium is slightly aerobic or anaerobic, and grows best in anaerobic environment.The optimum growth temperature is 44-45 ℃, the growth is slow and weak at 25-35 ℃, and the growth stops at 15 ℃.[9]
This bacterium has strict nutritional requirements. It does not grow well on most media and cannot grow on nutrient agar, so it is difficult to cultivate this bacterium.Generally, they are cultured on whey agar plates, and the colonies are irregular round, gray white, 1-3 mm in size. The colonies have curly hair like structure, and they are rhizoid when viewed under the microscope.It grows well in milk.Produces lactic acid.[9]
This strain ferments lactose, galactose and glucose to produce acid and lactic acid.It is very similar to Lactobacillus lactis in morphology and many characteristics, but there are fewer fermented sugars than Lactobacillus lactis. Therefore, some people believe thatLactobacillus bulgaricusProbablyLactobacillus lactisA mutant or variety of.[9]
Lactobacillus bulgaricusIt is one of the preferred and most commonly used strains for yogurt manufacturing.[9]
Lactobacillus lactis
This bacterium is a long bacterium, and its width is not more than 2μm. The length is variable, and it is usually coiled and interwoven together in the form of filaments. When young, it is single or in pairs.Gram staining positive, no movement, no spores, methylene blue staining shows that there are metachromatic particles in the bacteria.[9]
Slightly aerobic or anaerobic, with 5% COtwoIt grows well under the condition of.When containing peptone, glucose, yeast extractTwain 80It grows well on the tomato juice culture medium, the colony is usually rough, 1-3mm in diameter, white to light gray, dense or fluffy.The optimum growth temperature is 37-40 ℃, the maximum growth temperature is 48 ℃, and growth stops at 15 ℃.The suitable pH value is 6, the milk is coagulated, and the final acid production is about 1.6% lactic acid, which is produced by homotypic fermentationD-lactic acid。[9]
Lactobacillus can be isolated from milk and cheese, and is commonly used in cheese manufacturing.[9]
Lactobacillus acidophilus
The fungus is rod shaped, with blunt round ends,Gram staining positiveThe bacteria of the aged culture are uneven, showing bipolar staining.The cell size is about 0.6-0.9X1.5-6.0μm. It is single, arranged in pairs or in short chains, non motile, and does not produce spores.[9]
Lactobacillus acidophilus
This bacterium isMicroaerobic bacteriaIn general, it can grow.The most suitable culture temperature is 35-38 ℃, 15-22 ℃ can not grow or the growth is very weak, 48-55 ℃ may grow or grow.The optimum pH is 5.5-6.0, and the pH is required to be 5-7 at the initial stage of growth.It can grow in 2% NaCl and 2% bile salt.[9]
The nutritional requirements are complex, including amino acids, pantothenic acid, riboflavin, nicotinic acid, and folic acid. Thiamine is not required.Adding glucose, yeast extract and whey to the culture cluster can promote its growth.It grows well in milk and whey.In agarPlate culture mediumThe upper colony is rough, small, irregular, round, slightly raised, grayish white, and translucent. When observed under the microscope, it is uneven, glass frosty, filamentous edge, or curly hair.[9]
Some strains can ferment glycogen, and some strains can fermentMelibiose, raffinose, or bothDL lactic acid。It can produce 0.3-1.9% lactic acid due to the uncertainty of milk coagulation and acid production.[9]
Key values
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Lactobacillus plays an important role in maintaining human and higher animal health.In nutritional physiology, Lactobacillus can improve the digestion and absorption of protein, lactose, calcium and other nutrients, and produce a variety of vitamins for the body's digestion and absorption;It can inhibit the reproduction of putrefactive bacteria and pathogenic bacteria in the intestinal tract, reduce the content of blood ammonia and cholesterol, and maintain the balance of intestinal flora.Lactobacillus has immunomodulatory effects, such as significantly promoting cell division, promoting antibody production, activating macrophages, inducing the production of interferon, etc., and improving the disease resistance of the body.Lactobacillus can activate macrophagesmacrophageThe cytotoxicity was increased.Moreover, lactobacillus can induce humanPeripheral blood mononuclear cells(PBMC) produces IL-12, IL-18 andγ-Interferon to induce Th1 type cellular immune response.In addition, lactic acid bacteria can inhibit the hydroxymethylglutarate coenzyme A reductase, reduce the absorption of intestinal cholesterol, and thus reduce the cholesterol content in the body.Many studies have also proved that lactic acid bacteria can reduce serum cholesterol andtriglycerideRole of.Lactobacillus against stomachepithelial cellsWith high affinity, it can compete with pathogenic bacteria for adhesion sites to produce lactic acid, acetic acid, acetic acid and other organic acids, which are widely distributed in the digestive tract mucosa, play a barrier role in the adhesion of pathogenic bacteria and other mechanisms to antagonize pathogenic bacteria, and produce organic acid cytokines like proteins and other substances and affect the related metabolism of bacterial toxins, playing a protective role in the gastrointestinal tract.[5]It is worth pointing out that the role of Lactobacillus is strain specific, and even the traditionally safe Lactobacillus strains cannot guarantee the safety of all strains within the species, so it is very important to identify and detect Lactobacillus.[6]
Lactobacillus is also one of the normal symbiotic bacteria in the animal digestive tract and vagina, which has a certain inhibitory effect on the growth and reproduction of harmful microorganisms.[2]
Lactobacillus carries many invisible plasmids, which can be used for gene manipulation in Lactobacillus.[8]
Main hazards
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Of course, it is also harmful to biology. For example, it can ferment sugars like streptococcus in the mouth, produce acid, dissolve tooth enamel, and form caries.[2]It plays an important role in promoting the development of caries.The bacteria closely related to caries are mainlyLactobacillus casei、Lactobacillus acidophilus、Lactobacillus fermentans。However, it is beneficial in the digestive tract and vagina to promote the absorption of digestive nutrients, stimulate immune activity and preventVaginal infection。[3]
application
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Lactobacillus has been widely used in food, beverage, feed, medicine and other fields.[5]
Mainly used for lactic acid drinks, fermented milk, ethanol, etc.It is also used for micro determination of some vitamins and amino acids.Lactic acid bacteria can also be used for vacuum packed meat.High concentration freeze-dried powder made from lactobacillus digestans can effectively prevent corrosion.Add 10 to meat productssix-10sevenPer gram, it can inhibit the cold adapted hyphae, and it can remain unchanged within 9 weeks, but it is not heat-resistant.The use has been approved by EU countries.[1]
Lactobacillus powder
Lactobacillus functional food mainly includes active bacteriaMicroecological preparationAnd fermented food.Lactobacillus can be expanded, concentrated and separated to obtain the cell body, which can be made into capsules or tablets after adding protective agent and freeze-drying.But the product form ofBifidobacteriumThe active powder is mixed to make a microbial microecological preparation.Lactobacillus fermentation includes fermented food containing living bacteria and food that can be preserved for a long time after sterilization after fermentation.Lactobacillus seldom ferments with single bacteria, and is often associated with Lactobacillus, Streptococcus lactisStreptococcus thermophilusMixed fermentation with acidophilic yeast and bifidobacteria.[10]
historical origin
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lactobacillusIt has a long history. As early as the 19th century, it was mentioned in the Genesis of the Old Testament that Arabs lived long by drinking yogurt.In 1857 AD, Louis Pasteur began to describe the existence of tiny organisms in yoghurt in a scientific way.In 1873, Joseh Lister isolated and identified the microorganism as Bacteriumlacis from yoghurt.
