Lactobacillales

Lactobacillus sp.

The lactic acid bacteria ( Lactobacillales, lactobacilli or sour milk bacteria ) form an order of Gram-positive, anaerobic always but usually aero -tolerant bacteria, which are characterized in that they break down sugars to lactic acid ( lactic acid fermentation).

Features

In morphological respects, lactic acid bacteria hardly resemble each other, but are so far physiologically uniform to describe, as they rely on carbohydrates for energy. To produce homofermentative bacteria only end product is lactic acid and heterofermentative lactic acid bacteria in addition to lactate or to a significant portion of other end products, mostly ethanol and carbon dioxide. From other also lactic acid producing bacteria, the lactic acid bacteria differ in that they are metabolically unique to fermentation in the position which they perform even in the presence of oxygen. Due to their specialization on the growth in milk and similar nutrients and supplinreichen environments lactic acid bacteria have lost the ability to synthesize many vital substances, such as amino acids and to the necessary for respiration processes porphyrins and cytochromes. Among other things, they do not form catalase; that is, they can not cleave H2O2. One can, therefore, only the lactic acid bacteria in the gut or in mucous membranes of mammals find, just as in living or decaying plants, milk and all the places that come into contact with milk.

Bacterial count in raw milk

At the dairy Delivered cow's milk ( raw milk ) is divided by the milk quality Regulation in EU grades: with less than 100,000 cells / ml corresponds to the milk of grade 1, about the Grade 2 These average values ​​are recorded over a longer period of time. Currently you can from an average of 20,000 cells / ml milk out (Source: National Association of Bavarian Dairy Association ). About the number of bacteria addition, the delivery of milk even in terms of fat and protein content, inhibitors (antibiotics), freezing (water content ) and the number of somatic cells ( udder health) tested. However, these parameters are not related to the number of lactic acid bacteria.

One-quarter to one-half of the nuclei are lactic acid bacteria. If the udder of cows cleaned at the beginning of milking by hand, so that milk can often be bacteria than that of fully automated milked cows.

In a warm environment ( 20-30 ° C), untreated milk after about ten hours acidified with approximately one million organisms per milliliter. By the acid, the milk protein is precipitated, so that a thickening of the milk occurs. Fresh milk is therefore immediately after milking to max. 6 ° C and cooled as it inhibits the growth of bacteria.

Relevance to humans

Lactic acid bacteria are among the most important representatives of the human intestinal flora, as well as the vaginal flora. Some species are pathogenic. Streptococcus pneumoniae is a pathogen that can cause pneumonia, inter alia, Streptococcus mutans is involved in the development of caries. Lactic acid bacteria can be incorporated into skin cells and convert them into multipotent cells.

Different species and subspecies ( strains) of lactic acid bacteria in the preservation of food, such as yogurt, kefir, sour milk, cheese as well as in sauerkraut, used in Gimchi and in baking, for example, the leaven or for skin care and prevention of caries. The advertising writes the regular consumption of to " Lactobacillus casei - containing products ( defensis / Shirota ) " special effect.

Lactic acid bacteria are often used as a probiotic.

System

To order the Lactobacillales include the families

The exact classification of lactic acid bacteria is partly controversial. Thus one finds in various sources, also the family Oscillospiraceae, but which, for example is not performed in the important work of reference to the phylogenetic systematics of prokaryotes, Bergey's Manual of Systematic Bacteriology. Incertae sedis to the genera are here: Acetoanaerobium, Oscillospira and Syntrophococcus counted.

Important types are:

  • Lactobacillus acidophilus, a part of the normal vaginal flora
  • Lactobacillus bulgaricus - used for yogurt recovery
  • Lactobacillus casei
  • Lactobacillus crispatus and Lactobacillus iners, the main constituents of the normal vaginal flora
  • Enterococcus faecalis - a harmless inhabitant of the human gut
  • Lactobacillus helveticus - for cheese making
  • Leuconostoc mesenteroides - used for sauerkraut recovery
  • Lactobacillus plantarum
Firmicutes Anaerobic organism Intestine Soured milk Kimchi Digital Object Identifier
494624
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