Peroxidase of propionic acid bacteria

The peroxidase activity was found in Propionibacterium shermanii. Methods were developed to isolate and purify the enzyme. It was shown to be a heme-containing protein, specific to H2O2, stable at 20 to 30 degrees C and exerting the optimal action at pH 6.8 to 7.0. The rate of the enzyme-catalysed reaction was studied as a function of the enzyme and substrate concentrations. The Km was determined for H2O2 and o-dianisidine.     

Conditions for porphyrin formation by propionic acid bacteria

Porphyrin production by seven species of propionic acid bacteria (Propionibacterium shermanii, its mutant P. shermanii M-82, P. technicum, P. vannielii, P. rubrum, P. thoenii and P. jensenii) was being studied. All the bacteria were cultivated on a glucose-peptone medium. A positive correlation between the amount of the produced porphyrins and the vitamin B12-synthetizing activity was observed for the most of species. Exogenous delta-aminolevulinic acid stimulated the porphyrin accumulation, but the degree of its utilisation decreased as its content in the culture medium increased from 5 to 200 mg/l. A maximum synthesis of porphyrins by P. shermanii M-82 (mainly of coproporpyrin III) was observed at definite concentrations of glucose and cobalt salts.     

Antimutagenicity of propionic acid bacteria]

The antimutagenicity of the cell extracts of Propionibacterium shermanii VKM-103, P. pentosaceum CCM 1859 and P. acnes CCM 3322 against mutagenicity of sodium azide and N-methyl-N'-nitro-N-nitrosoguanidine was demonstrated for the first time. The extracts of propionic acid cocci didn't show such effect. The antimutagenic factor acts as a desmutagen, has polypeptide nature and evidently is an enzyme (enzymes). The inhibitory effect of the extract is due to the presence of more than one protein factor in it.     

Antimutagenicity of propionic acid bacteria.

The antimutagenic effect of dialysed cell extracts of 4 strains of propionic acid bacteria was examined against the mutagenicity of sodium azide in the TA1535 tester strain of Salmonella typhimurium using the Ames test. It was noted that dialysates of 2 strains of Propionibacterium shermanii, P. pentosaceum and P. acnes, significantly reduced sodium azide-induced revertants. The dialysate of propionic acid cocci did not show an antimutagenic effect. The inhibitory activity was enhanced if the mutagen and extract were coincubated for 20 min prior to performing the mutagenicity assay. Antimutagenicity of dialysates from P. shermanii VKM-103 against MNNG and 9-aminoacridine was shown in S. typhimurium strains TA1535 and TA97. The antimutagenic activity was found in the protein fraction of the cell extract of P. shermanii. The proteins of the dialysate of P. shermanii were separated using a Toyopearl gel column into 3 main peaks according to their molecular weights. The antimutagenic activity towards sodium azide was found in the second and the third peaks. We suggest that dialysates of the cells of propionic acid bacteria contain several kinds of antimutagenic substances with different molecular weights.     

Influence of different vitamin-nitrogen sources on cell growth and propionic acid production from sucrose by Propionibacterium shermanii

Cell growth and organic acid production by Propionibacteria are dependent on the vitamin-nitrogen source in the culture medium. Final cell and propionic acid concentrations produced by Propionibacterium shermanii, using corn-steep liquor, were higher than those obtained utilizing yeast extracts. Since corn-steep liquor is much cheaper than yeast extract, the process becomes more attractive. By calculating the specific growth rates, it was observed that the critical propionic acid concentration, that prevents all growth (μ_X = 0), is different depending on the vitamin-nitrogen source used and its concentration. For example, for 5.0 and 15.0 g/l Oxoid yeast extract, those critical propionic acid concentrations were 16.0 and 27.0 g/l, respectively. Such propionic acid concentrations inhibit the cell growth, but not the formation of acid. The specific propionic acid production rate also indicates that the critical concentration for metabolic activity, when propionic acid is no longer produced (μ_P = 0), varies according to the vitamin-nitrogen source and its concentration in the medium. For 5.0 and 15.0 g/l Oxoid yeast extract, those concentrations were 22.1 and 30.1 g/l, respectively.     

Characteristics of the sulfate requirement of propionic acid bacteria

The kinetics of sulfate assimilation by Propionibacterium shermanii was found to be peculiar. The assimilation and excretion of sulfate into the medium had an oscillatory character. Sulfate was shown to pass into the cell by active transport. Sulfate transport is described by the Michaelis--Menten kinetics. Thiosulfate and sulfite inhibit sulfate assimilation. Cysteine does not entirely inhibit sulfate assimilation by the cells. The system of sulfate transport was repressed by cysteine to a small extent. The intracellular pool of inorganic sulfate changed in the process of culture growth.