Propionic acid bacteria properties

The fermentation products of the bacteria include some lactic acid and some of the short-chain fatty acids such as butyric, acetobutyric, and propionic acids. Bacteria contain enzymes that split the bile salt, and as a result the detergent properties of bile are lost adding to malabsorption. 

All propionic acid bacteria are catalase-positive P. arabinosum displays a very weak catalase activity). As a rule, members of the genus Propionibacterium produce significant amoxmts of vitamin Bn. We (Vorobjeva, 1976) suggested to differentiate propionibacteria by the nature of the coenzyme form of vitamin Bn. The presence of the isomerization reaction of succinyl-CoA methylmalonyl-CoA, which is the key reaction of propionic acid fermentation, represents another valuable taxonomic property of the genus. 

Owing to the absence of toxicity and valuable biotechnological properties, propionic acid bacteria are widely used in industry (food industry, vitamin B]2 production). Genetic approaches may help increase strain productivity, change nutrient requirements, confer phage resistance. 

It was also found that the direction of sulfate fluxes in or out of the cell depended on its intracellular pool. When sulfate-depleted cells were transferred to a new medium, they actively accumulated sulfate first, but then started to release it (Fig. 4.2). Cells grown first in the medium high in sulfate, when transferred to a fresh medium, started to release sulfate at once. Interestingly, such an oscillatory pattern of sulfate utilization was not a common property of all propionic acid bacteria. For instance, P. petersonii steadily took up sulfate from the medium, while the two closely related strains, P. shermanii and P. freudenreichii, showed an oscillatory pattern of sulfate consumption, like the distantly related E. coli (Fig. 4.3). 

Wood HG and Workman CH (1940) The relationship of bacterial utilization of CO2 to succinic acid formation. Biochem J 34 129-137 Wood HG, Stone RW and Workman CH (1937) The intermediate metabolism of the propionic acid bacteria. Biochem J 31 349-359 Wood HG, Allen SHG, Stjemholm R and Jacobson B (1963) Transcarboxylase. III. Purification and properties of methylmalonyl-oxaloacetic transcarboxylase containing tntiated biotin. J Biol Chem 238 547-556... 

In a sense, propionic acid bacteria are domesticated bacteria. They might have been used for cheese making as early as 9000 years BC. In the last 40 years their practical uses have expanded to include vitamin Bn and propionic acid production, bread baking, starters for ensilage and some pharmaceutical preparations. New prospects for their future uses are also emerging, based on the useful properties recently discovered. 

The propionic acid bacteria have many interesting properties. 

PH As are aliphatic biopolyesters produced by numerous bacteria The most commonly found and best studied PHA is poly-P-hydroxybutyrolactone (PHB) made in high yield by fermentation of glucose [14,17,18]. A copolymer with hydroxyvalero-lactone (PHBV) results when the fermentation is carried out in the presence of some propionic acid. The properties of PHB are often compared with PP and poly(ethylene terephthalate) (PET) (Table 15.4). PHBV is more easily processed than PHB, but... 

Bacteria from the genera Lactobacillus and Streptococcus are involved in the first steps of dairy production (3). The raw materials produced by their effects usually only acquire their final properties after additional fermentation processes. For example, the characteristic taste of Swiss cheese develops during a subsequent propionic acid fermentation. In this process, bacteria from the genus Propionibacterium convert pyruvate to propionate in a complex series of reactions (2). 

Organic acids may exhibit other sensory properties. For example, citric acid possesses sweet-and-sour sensory notes, and succinic acid has a salty-bitter taste. On the other hand, the typical taste and flavor of Emmental cheese can be ascribed to the propionic acid and a few other compounds, such as proline. In fact, taste and flavor result from the combination of different food constituents in definite proportions. Raw meat smells much like lactic acid, which arises from postmortem anaerobic glucolysis and determines the pH of meat, its final properties, and microbial stability. This same organic acid has been related to the inhibition of certain pathogenic bacteria in yogurt (3). Table 1 lists the reported threshold concentrations for various organic acids in different media (4-6). 

The most important property of the genus Propionibacterium is the production of propionic acid as a result of the propionic acid fermentation dependent on coenzyme B12. If the dependence on coenzyme Bn is disregarded, some clostridial strains that do not form spores may be erroneously attributed as propionibacteria. For example, Cl botulinum, Cl propionicum and some other species can produce propionic acid, but propionibacteria have the GC-type DNA (65-67 mol% G+C in classical and 53-62 mol% in cutaneous bacteria), while clostridial DNA is of the AT-type (25-30 mol% G+C). 

The property of storing a polysaccharide within its cytoplasm is characteristic of the bacteria associated with the hydrolysis of starch in both the rumen and the caecum. Cl. butyricum is known to produce an amylase in vitrOy and a free amylase that occurs in the rumen of starch-fed sheep is presumably of bacterial origin, as no amylase is present in sheep s saliva. Similarly an amylase is produced in vitro by starch-splitting cocci, and although this enzyme hydrolyzes starch as far as the dextrin stage the end products of fermentation include acetic, propionic, and butyric acids. 

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