Clostridium tyrobutyricum
| Clostridium tyrobutyricum | ||||||||||||
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| Clostridium tyrobutyricum | ||||||||||||
| van Beynum & Pette 1935 |
Clostridium tyrobutyricum is a spore-forming bacterium whose spores are heat-resistant. It occurs in large numbers in the silage used as feedfor cows . It belongs to the genus Clostridium , whichincludesnumerous pathogens , but is not considered to be pathogenic .
Occurrence
Clostridium tyrobutyricum occurs in the soil, from where it is spread further with the help of the endospores and thus reaches plants that are used to make silage. It can be isolated from this and has also been found in dairy products such as Emmental cheese , into which it got through the cow's milk after being fed contaminated feed. The contamination does not take place in the cow's body, but outside through soiled udders, the stable air, equipment or hands to which the spores from the silage adhere or in which they can occur.
features
As typical representatives of the clostridia, the bacteria grow anaerobically and are therefore catalase- negative and oxidase- negative. They are gram-positive , show a rod-shaped shape in the microscopic image and are mobile through peritrichally arranged flagella .
Under unfavorable environmental conditions they are able to form endospores . These are larger than the vegetative cells and lead to a bulge in the mother cell. The spores are also characterized by thermal resistance: While most vegetative bacterial cells are killed by briefly heating them to temperatures of around 80 ° C ( pasteurization ), this heating does not damage the endospores, they remain viable and can germinate again.
The species name indicates that this species forms butyric acid through fermentation , butyrates are the salts of butyric acid. The genome of Clostridium tyrobutyricum (strain DSM 2637) is currently being sequenced.
The temperature optimum for cultivation of C. tyrobutyricum is from 40.2 to 43.3 ° C, therefore, the bacterium is one likely to be thermophilic organisms. It no longer grows at 10 ° C, but the cells survive this temperature and begin to multiply again at slightly higher temperatures (12–15 ° C). The pH for the growth of most of the strains studied is in the range of pH 5.5 to 7.5. C. tyrobutyricum is able to tolerate moderate concentrations of sodium chloride , a content of 2.0% does not prevent growth, a content of 3.0% still allows some of the strains examined to multiply and only from a sodium chloride content of 3 .5% growth is no longer possible. These results allow an estimation of the conditions under which the undesired growth of Clostridium tyrobutyricum can be expected in cheese production.
metabolism
Clostridium tyrobutyricum utilizes carbohydrates through fermentation . First, there is a gradual breakdown of monosaccharides (simple sugars) such as D - glucose (grape sugar) in glycolysis to pyruvate . Under anaerobic conditions, the NAD + (nicotinamide adenine dinucleotide) consumed in the process must be regenerated; this is done through butyric acid fermentation . In the fermentation of C. tyrobutyricum, pyruvate is converted into butyrate (salt of butyric acid ), acetate (salt of acetic acid), carbon dioxide (CO 2 ) and elemental hydrogen (H 2 ).
Butyric acid fermentation takes place in many clostridia, but as a special feature, C. tyrobutyricum can also use lactate (the salt of lactic acid ) as a substrate instead of glucose . Lactic acid is produced by representatives of the Lactobacteriaceae in lactic acid fermentation and lowers the pH of the environment. Most clostridia only grow in neutral or alkaline media, the presence of lactic acid bacteria suppresses their growth. Clostridium tyrobutyricum, on the other hand, tolerates a slightly acidic environment (up to around pH 5.0) and is also able to generate energy from the degradation product of the lactic acid bacteria itself.
proof
The bacterium can be cultivated in a nutrient medium that contains meat extract , yeast extract , peptone from casein , glucose and other components. It is important that the medium is anoxic before inoculation , since oxygen is toxic to the cells of C. tyrobutyricum . This is achieved by boiling and cooling in a nitrogen atmosphere , which excludes the presence of oxygen from the air. Strict adherence to the anaerobic technique must also be observed during inoculation and incubation . It is incubated at a temperature of 37 ° C.
Biochemical tests for identification include, as already described, the catalase and oxidase test , as well as typical tests from a "colorful series" , which examine, among other things, the usability of various carbohydrates and other substrates. A rapid determination system based on this in miniature format ( Analytical Profile Index ) for the determination of anaerobes is commercially available and also includes the detection of Clostridium species. These classic microbiological and biochemical detection methods are very time-consuming, so that there is now also direct detection of Clostridium tyrobutyricum using the multiplex PCR method. It ensures the differentiation from other Clostridium species.
Industrial importance
Clostridium tyrobutyricum is feared as the cause of incorrect fermentation in cheese production . The germ can be introduced into the animal via silage as feed for the cows and gets into the cheese via the milk. During the production of silage, the suitable plant parts are chopped up, compacted in the silo and sealed airtight. The aim is now to lower the pH value quickly, as is the case with lactic acid fermentation , while maintaining the anaerobic atmosphere. The low pH value and the absence of oxygen prevent the growth of numerous microorganisms that are harmful to the production of the silage. This also applies to most clostridia, but not to C. tyrobutyricum , which tolerates weakly acidic pH values and can also metabolize lactic acid as a substrate.
The silage thus either still contains vegetative cells or the spores of the bacterium. The spores get into the cow's organism via the feed and from there directly into the milk, or this happens through contamination of the udder with spore-containing material. Even if the milk is pasteurized before the cheese is made, at least the spores are not killed so that they are contained in the cheese and can germinate again inside the cheese wheel. During the butyric acid fermentation that now takes place, the lactic acid that is also present in the cheese is broken down into butyric acid, carbon dioxide and hydrogen. The gases carbon dioxide and hydrogen cause the cheese to a strong flatulence ( late blowing , in English as late blowing called), which manifests itself as cracks and crevices in the Käsekrume and nothing with in some cheeses such. B. Emmentaler, desired holes in the cheese has to do. The butyric acid also causes an unpleasant odor. These cheeses are inedible, no longer usable and lead to high financial losses in cheese production.
Milk from cows that are fed with silage is not suitable for cheese production because of the risk of incorrect fermentation. In Switzerland, therefore, no silage is used in cheese-making milk . In the EU, lysozyme , an enzyme obtained from chicken protein, is approved as an antibacterial agent in the cheese industry. As a food additive with the number E 1105, it may only be used for matured cheese in order to prevent damage due to incorrect fermentation of Clostridium tyrobutyricum .
Individual evidence
- ↑ a b c Catalog of microorganisms. Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures, accessed on March 3, 2013 .
- ↑ a b Michael T. Madigan, John M. Martinko, Jack Parker: Brock Mikrobiologie. German translation edited by Werner Goebel, 1st edition. Spektrum Akademischer Verlag GmbH, Heidelberg / Berlin 2000, ISBN 978-3-8274-0566-1 .
- ↑ Johannes Krämer: Food microbiology. 3. Edition. Verlag Eugen Ulmer Stuttgart, 1997, ISBN 3-8252-1421-4
- ↑ a b c d Hans G. Schlegel: General microbiology. 7th edition. Thieme Verlag, Stuttgart / New York 1992, ISBN 3-13-444607-3
- ↑ Clostridium tyrobutyricum DSM 2637 on the website of the Genoms Online Database (GOLD). Retrieved March 3, 2013 .
- ↑ a b c M. Ruusunen, A. Surakka, H. Korkeala, M. Lindström: Clostridium tyrobutyricum strains show wide variation in growth at different NaCl, pH, and temperature conditions. In: Journal of food protection. Volume 75, Number 10, October 2012, pp. 1791-1795, ISSN 1944-9097 . PMID 23043827 .
- ↑ ID 32 biochemical identification (rapid ID 32 A); Anaerobes on the website of bioMérieux Deutschland GmbH. (No longer available online.) Archived from the original on January 4, 2014 ; Retrieved March 3, 2013 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ P. Cremonesi, L. Vanoni et al. a .: Identification of Clostridium beijerinckii, Cl. butyricum, Cl. sporogenes, Cl. tyrobutyricum isolated from silage, raw milk and hard cheese by a multiplex PCR assay. In: The Journal of dairy research. Volume 79, Number 3, August 2012, pp. 318-323, ISSN 1469-7629 . PMID 22850580 .
- ^ F. Driehuis, SJ Oude Elferink: The impact of the quality of silage on animal health and food safety: a review. In: The Veterinary quarterly. Volume 22, Number 4, October 2000, pp. 212-216, ISSN 0165-2176 . PMID 11087133 . (Review).
- ↑ a b Product information: inovapure (Lysozyme) on the website of Neova Technologies Inc., Canada. (No longer available online.) Archived from the original on February 16, 2013 ; Retrieved March 3, 2013 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ^ P. Kuhnert, B. Muermann, U.-J. Salzer (Ed.): Handbook of Food Additives, Volume 3 (loose-leaf collection), Behr's Verlag
