Strains Of Propionic Acid Bacteria Research Articles

Jerusalem Artichoke Tuber Processing: Influence of Pre-Treatment Methods, Lactic Acid, and Propionic Acid Bacteria Strains on Functional Fermented Beverage Production.

Fermented plant-based products are rapidly gaining popularity. Jerusalem artichoke is a medicinal plant that can be used to make fermented beverages. Samples were subjected to pretreatment (ultrasound at 35kHz for 2, 4, and 6min, freezing at -80°C and -17°C) while an untreated sample was used as control. It was shown that all types of pretreatments did not lead to an increase in protein, solids, polyphenols, and carbohydrates compared to the control sample. The greatest decrease in the values of these indicators occurs when pre-freezing tubers are used for Jerusalem artichoke dispersion production. It was also found that samples frozen at -80°C had a significantly higher concentration of Ca, Si, Mg, and P whereas untreated samples frozen at -17°C had more Al, K, Cu, Sr, and Cr. The processing method can affect the sensory descriptors of Jerusalem artichoke tuber dispersions to different extents, but the preference was for the control sample without pre-treatment. The fermentation of Jerusalem artichoke tuber dispersions demonstrated that S. thermophilus induced the most rapid fermentation (pH 4.75 in 5h). The highest antioxidant activity after fermentation (55.39% FRSA) was shown for L. acidophilus H9, while the highest % FRSA value during the storage period was for L. bulgaricus (67.5%) on day 5 after fermentation. The highest viability among all selected microorganisms was detected for L. bulgaricus, L. acidophilus AT-41, and B. coagulans MTCC 5856 with the increase in biomass content by 2.3, 2.27, and 2.12 log10CFU/ml after fermentation. According to the results of sensory evaluation using hybrid hedonic scale the best results were shown for samples fermented with L. bulgaricus.

Influence of propionic acid microorganisms on the quality indicators of the produced sausage

The article considered the effect of probiotic bacteria on the quality of meat for semi-smoked sausages. The biochemical activity of propionic acid bacteria was studied at the stage of the production process of semi-smoked sausages after the treatment of raw materials with starter microorganisms. We also studied the effect of salt, and sodium nitrite on the development of propionic acid bacteria in raw beef. The results of the technology of production of semi-smoked sausages treated with propionic acid bacteria in the amount of 0.1%, and the quality characteristics of the finished sausage products are presented. On the basis of experimental studies optimal technological parameters of salting and precipitation in the production of fermented semi-smoked sausages were selected. The use of liquid propionic acid bacteria (2 strains of propionic acid bacteria Propionibacterium shermani) in the amount of 0.1% will give a decrease in the production time of half-smoked sausages by two times. As a result of the research it was proved that the introduction of 2 different strains of propionic acid bacteria concentrate into raw meat accelerates biochemical changes in the process of salting and provides functional and technological properties. Also, the results of the study showed that propionic acid bacteria used in the technology of semi-smoked sausages are resistant to the amount of food salts and sodium nitrite used. As a result of research, a better way of using liquid propionate microorganism in the production of semi-smoked fermented sausages was adopted.

Selection of probiotic microorganisms in the composition of a new biological preparation for farm animals

The idea of a healthy diet is gaining popularity, which justifies consumer interest in environmentally friendly and biologically complete livestock products. In this regard, the development and use of probiotic preparations in feeding farm animals and identifying the effectiveness of their use is an urgent task of our time. An essential step in creating new biological products is the study and selection of strains for the composition of the starter since the probiotic effect of microorganisms is determined by the set of natural properties they possess. In this work, the biological and technologically valuable properties of 12 strains of lactobacilli and 15 strains of propionic acid bacteria from the Siberian collection of microorganisms of the laboratory of the microbiology of milk and dairy products of the SRICM FGBNU FANZA (Siberian Research Institute of Cheese Making of Federal State Budgetary Scientific Institution of Federal Altai Scientific Center for Agrobiotechnology) department were studied to include them in the composition of a new probiotic preparation for farm animals. During the research, it was found that all strains of lactic acid rods actively fermented carbohydrates found in plant substrates and maintained their numbers not lower than a therapeutically significant level during 60 days of storage, i.e., showed high technology. Propionic acid bacteria exhibited high biological properties, i.e., they could produce vitamin B12 in amounts from 0.48 to 0.64 μg/cm3 and maintained their viability during six months of storage. As a result of research on the best manifestation of technologically valuable properties, two strains of lactic acid bacilli (SKM673 and SKM-681) and three strains of propionic acid bacteria (111, 112, 149) were selected that were promising for inclusion in the composition of a new probiotic preparation for farm animals.

Features of selection of microorganisms in the composition of a new probiotic drug for farm animals

Nowadays, the idea of healthy eating is gaining popularity, which makes consumers interested in environmentally friendly and biologically nutritious animal products. In this regard, the development of probiotic preparations for farm animals and determination of the effectiveness of their use become urgent tasks. Important stages in the creation of new biopreparations are the study and selection of the most suitable strains, as the probiotic effect of the microorganisms included in the inoculum is determined by a set of technologically valuable properties they possess. In the course of the study, technologically valuable properties of 12 strains of lactobacilli and 15 strains of propionic acid bacteria from the Siberian Collection of Microorganisms (Laboratory of Microbiology of Milk and Dairy Products, Siberian Research Institute of Cheesemaking, FSBSI “Federal Altai Scientific Center of Agrobiotechnologies”) were studied in order to include them in the composition of a new probiotic preparation for farm animals. It was found that all the considered strains of lactic acid bacilli actively digested carbohydrates included in the composition of plant substrates, as well as maintained their abundance not below the therapeutically significant level for 60 days. Propionic acid bacteria produced 0.48 ± 0.01 to 0.64 ± 0.06 μg/cm3 of vitamin B12 and remained viable in numbers of tens of millions of cells for 6 months. As a result, two strains of lactic acid bacilli (SCM 673, SCM 681) and three strains of propionic acid bacteria (111, 112, 149) were selected according to the best manifestation of technologically valuable properties as promising for inclusion in the composition of a new probiotic preparation for farm animals.

Propionic Acid Fermentation—Study of Substrates, Strains, and Antimicrobial Properties

Since milk whey is an abundant dairy by-product and a significant threat to the environment, its utilization is of great interest. The study compares valorization of lactose and lactates—the main carbon sources of whey—by fermentation—an environmentally friendly process. Antimicrobials released during fermentation by food-grade bacteria can help increase the microbiological safety of food. Propionic acid—a strong antimicrobial—is obtained mainly by the petrochemical route, yet there is increasing interest in its synthesis in biotechnological pathway. Five strains of propionic acid bacteria (Acidipropionibacterium acidipropionici, Propionibacterium cyclohexanicum, Propionibacterium freudenreichii, Acidipropionibacterium jensenii and Acidipropionibacterium thoenii) were investigated for their ability to produce organic acids and biomass using Na lactate or lactose as carbon sources. Selected fermentates were investigated for their antimicrobial efficacy during in vitro studies with foodborne pathogens: Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus. Results confirm that the production of acids and biomass is considerably influenced by the added carbon source. The tested fermentates have strong and specific antimicrobial activity against Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus. In addition, inhibition of Staphylococcus aureus and Klebsiella pneumonia depends on the activity of produced bacteriocins. The article also discusses the possibility of increasing the antimicrobial activity of fermentates by acidification.

A mixed culture of Propionibacterium freudenreichii and Lactiplantibacillus plantarum as antifungal biopreservatives in bakery product

In this study, 15 strains of Lactic acid bacteria (Allata et al.) and 6 strains of propionic acid bacteria (PAB) were firstly tested for their antifungal activity against three spoilage fungi, Aspergillus niger, Penicillium crustosum and Aspergillus flavus. Two strains of LAB and PAB were selected and assessed, alone or paired, for their abilities to inhibit the most resistant mold, Aspergillus niger. A mixed culture of P. freudenreichii D6 and L. plantarum L9 was found to be the most active and their optimal inoculum was 1 × 108 and 1 × 106 CFU/mL, respectively. Furthermore, the in situ antifungal effect of the mixed culture was evaluated against bakery product spoilage fungi. It was found that the growth of airborne fungi was delayed for up to 7 days. The cell number of L. plantarum L9 was slightly increased by the presence of P. freudenreichii D6. Quantification of three main acids (propionic, lactic and acetic acid) produced by the protective cultures suggested that acetic acid was mainly responsible for the antifungal activity. In conclusion, the mixed culture of P. freudenreichii and L. plantarum may be exploited as biopreservatives in bakery products.

Optimization of nutrient medium composition to increase biomass of propionic acid bacteria and acidophilic bacteria

Numerous studies have shown that it is very important that the microorganisms included in the composition be in a strong symbiotic relationship when selecting vents for fermented dairy products. Therefore, it is the primary task to identify the relationship between microorganisms in the preparation of the starter. Strains that retain biochemical activity for a long time, depending not only on external factors (composition of nutrient medium, temperature, etc.), but also on the ratio between biochemical active and inactive cells in populations of microorganisms, which determines the viability of the culture, its practical value, are considered valuable. Microorganisms of the genus Lactobacillus are widespread in nature and are members of human microflora. They have high biological and functional activity, which determines their practical use as probiotics and in food production. Propionic acid bacteria are considered as promising probiotics, the positive impact of which on human health is generally recognized. The scientific results show the expediency of using strains of propionic acid bacteria in the production of functional dairy bio-products for the purpose of enrichment with probiotics cells and their useful exometabolites. As a result of the co-cultivation of propionic acid bacteria and acidophilic bacterium, a stable microbial association with high probiotic and biotechnological properties (inoculum) has been developed. A scheme for preparing an inoculum for producing a bacterial concentrate using pure cultures of propionic acid bacteria and an acidophilic bacterium has been developed. This article presents the results of studies on the selection of nutrient medium in order to increase the yield of biomass and the accumulation of certain metabolic products by microorganisms.

Propionic acid bacteria enhance ruminal feed degradation and reduce methane production in vitro

ABSTRACT Thirty-one strains of propionic acid bacteria were screened for their effects on methane production and volatile fatty acid concentrations using in vitro assays of rumen fluid from Norwegian dairy cows and a grass silage–concentrate mixture as substrate. Nine of 31 strains were further analysed for effects on substrate degradation. Propionic acid bacteria led to reductions of up to 20% in methane production. Seven strains stimulated volatile fatty acid production, and in their presence in vitro substrate degradation tended to increase (P < .10). Most consistent results were found with Propionibacterium thoenii T159, which reduced methane production by 20% and caused 8% and 21% overall increases in substrate degradation and total volatile acid production, respectively (P < .05). Concomitant beneficial effects of a reduction in methane emissions and an increase in feed degradation suggest that this strain may be a promising tool for improving the productive performance of dairy cows.

Evaluación del efecto antifúngico de metabolitos de cultivos bioprotectores: aplicación en derivados lácteos

To guarantee the food safety and shelf life of many processed food products, the food industry has made use of artificial preservatives that are each time more questioned and replaced by natural alternatives such as bioprotective cultures. Lactic acid bacteria (LAB) and propionic acid bacteria (PAB) are bacterial groups recognized by their antimicrobial action against bacterial pathogens but their activity against fungi is lesser known. The present study evaluated the antifungal functionality of three strains Lactobacillus casei, three of L. rhamnosus, and three of Propionibacterium freudenreichii against isolates of Mucor circinelloides and Geotrichum candidum and the effect of factors like pasteurization (74°C, 3 min) and culture media (milk and BRFS) on it. The challenge assays in dairy models (yogurt agar) produced the following results in accordance to a qualitative score scale of fungal growth: (1) different strains of LAB and PAB differed in the bioprotective functionality, (2) the heat treatment eliminated or reduced substantially the antifungal power with the exception of P. freudenreichii subsp. shermanii BPL0082, and (3) the cultures developed in media BRFS exhibited greater inhibition capacity.

Characterization and stress-protective action of Saccharomyces cerevisiae extracellular peptide factors on propionic acid bacteria

Protective effect of Saccharomyces cerevisiae exometabolites (RF1 and RF2) on seven strains of propionic acid bacteria under exposure to bile salts and acid stress was studied. RF2 had a stronger protective effect than RF1. Comparison of the analytical profiles of RF1 and RF2, separated by RP-HPLC, showed that nearly 80% of RF1 components were present in RF2. Separation of S. cerevisiae RF1 into individual components by means of semi-preparative RP-HPLC was used for structural characterization of the active component of the RF1 fraction. It was found to contain two pentapeptides (<1 kDa) with identical amino acid sequences (1Gly-Pro-Tre-Gly-Pro5), differing in one hexose residue. The RF2 separation method based on three-stage liquid chromatography at low and high pressure was developed, which involved analytical high-pressure gel chromatography. The use of the latter method made it possible to separate high-molecular components and perform enrichment of low-molecular peptides. Peptide origin of the RF2 active substances with molecular masses allegedly below 300 Da was confirmed.

Application of 16S-ARDRA and RFLP-PFGE for improved genotypic characterisation of dairy propionibacteria and combination with characteristic phenotypes

Propionic acid bacteria (PAB) are important for the manufacture of Swiss-type cheeses since they are involved in the formation of eyes and are responsible for the characteristic flavour and aroma of these cheeses. Propionibacterium freudenreichii is most commonly encountered in Swiss-type cheeses and is the sole Propionibacterium species used as a cheese starter. Aspartase activity determined in PAB is strain-dependent and it is important to find a usable way to identify the specific strains involved in cheese making. In this work, 16S-amplified ribosomal DNA restriction analysis and pulsed-field gel electrophoresis (PFGE) were used to differentiate 107 PAB strains. Consequently, the presence and persistence of inoculated Propionibacterium starter strains can be monitored during cheese ripening. The studied metabolic features of lactose utilisation, nitrate reductase activity and aspartase activity could not be directly associated with particular genotypes, but principal component analysis (PCA) suggested a linkage between related PFGE patterns and aspartase activity.

Characterization of propionic acid bacteria using matrix-assisted laser desorption/ionization (MALDI) mass spectrometry

It was shown that matrix-assisted laser desorption/ionization (MALDI) mass spectrometry could be used for the diagnostic characterization of propionic acid bacteria (PABs). The spectra of proteins (whole PAB cells) with a molecular mass of 3000 to 11 000 were obtained and analyzed using three matrices: sinapinic (SA), 2,5-dihydroxibenzoic (DHB), and α-cyano-4-hydroxycinnamic acid (HCCA). The MALDI spectra of PAB revealed the protein peaks characteristic of (1) the genus Propionibacterium (3496, 5386, 5605, 10 470), (2) the groups of species sharing the common composition of their cell walls and fatty acids, and (3) a species (four species were investigated). Exemplified by the P. shermanii strains (the collection and mutant ones) producing and not producing vitamin B12, the possibility of using MALDI profiles for strain differentiation was confirmed. The MALDI profiles of the propionic acid cocci of the genus Luteococcus differ substantially from the profiles of PAB strains of the genus Propionibacterium, which is an additional proof of the validity of whole-cell MALDI spectra for generic differentiation of bacteria. Our investigation shows that the bacterial groups determined using the MALDI profiles correlate with the phylogenetic 16S rRNA gene groups, thus demonstrating the high resolution of this method for the differentiation of intraspecific differences (subspecies, strains).

Characterization of Growth and Metabolism of Commercial Strains of Propionic Acid Bacteria by Pressure Measurement

AbstractDairy propionibacteria are essential starters for Emmental cheese manufacture. The behavior of three commercial strains of Propionibacterium freudenreichii subsp. shermanii (P.f. 1, P.f. 2 and P.f 3) were studied in a liquid medium under air and N2 atmosphere using an on‐line pressure measurement technique. Growth kinetics and metabolite production were characterized under conditions usually reported as “optimal conditions” (pH 6.5, NaCl 0 %, temperature 30 °C) and also evaluated under “stressful conditions” (pH 5.2, NaCl 2 %, temperature 20 °C) simulating the cheese ripening conditions. In both cases, the effects of oxygen on growth were strain‐dependent. Under “stressful conditions”, two of the three strains were inhibited by oxygen under conditions of air atmosphere, while all three strains grew under conditions of N2 atmosphere. In the latter case, the duration of the lag phase and the maximum rate of pressure variation were significantly different, however, no significant differences were found between the strains with regard to the total fermentation time. Under “optimal conditions” metabolite production was strain‐dependent. In an air atmosphere, all strains produced more acetate and CO2 and less propionate than in a nitrogen atmosphere.

Binding of Fusarium mycotoxins by fermentative bacteria in vitro

Fusarium toxins can occur in conserved forages impairing farm animal performances and health. On-farm biological decontamination methods could be an alternative to traditional physico-chemical methods. In this work, the ability to remove Fusarium toxins by fermentative bacteria was evaluated in vitro. Twenty-nine strains of lactic (LAB) and propionic acid bacteria (PAB) were tested for their ability to remove deoxynivalenol (DON) and fumonisins B1 and B2 (FB1, FB2) from an acid, pH 4, medium. Mycotoxin removal was widespread for LAB, but differences among strains were large. Removal was up to 55% for DON, 82% for FB1 and 100% for FB2. Selected strains were also capable of removing up to 88% zearalenone. The PAB strains were less efficient than the LAB. Binding, not biodegradation appeared to be the mode of action, as no toxin derivatives were observed and removal was not impaired in nonviable bacteria. Binding was not affected by pH, except for fumonisins that decreased to nearly 0% at neutral pH. Selected fermentative bacteria are able to bind main Fusarium mycotoxins. The binding ability of selected strains could be used to decrease the bioavailability of toxins in contaminated silages.

Possibilities for stimulation of Bifidobacterium growth by propionibacteria

Twenty-seven propionic acid bacteria (PAB) strains were studied for their ability to pro- duce metabolites, which stimulated the growth of six Bifidobacteriumstrains. In addition, the 27 in- vestigated PAB strains were examined for their influence on the growth of four Gram(-) strains belonging to species Escherichia coliand Yersinia enterocolitica, their abilities to survive at pH 2.0, 2.5, 3.0 and in the presence of 4% bile salts as well as their sensitivity against 12 selected antibiotics. All PAB strains stimulated growth of from 3 to 6 of the examined Bifidobacteriumstrains and simul- taneously produced antibacterial metabolites against Gram(-) rods. Fifteen PAB strains inhibited growth of the particular Bifidobacteriumstrains. Five PAB strains were resistant to acidity surviving for 2 h in pH 2.5 at population level 10 2 -10 6 cfu.mL -1 and 3 strains were resistant to bile salts. Only one PAB strain survived in both the acidic and the bile salt environments. All PAB strains were sensi- tive to a majority of the antibiotics used in the investigations. Bifidobacterium / Propionibacterium / Gram(-) rod / stimulation / inhibition

Contribution of propionic acid bacteria to lipolysis of Emmental cheese

Compared to many cheeses, lipolysis of Emmental is generally low. It concerns about 1-2% of cheese fat and the amount of free fatty acids (FFAs) varies from 2 to 7 g.kg -1 of ripened cheese. In this work, we studied the extent of lipolysis due to propionic acid bacteria (PAB). The re- lease of FFAs during the ripening of Emmental cheeses made from microfiltered milk, with or with- out propionic acid bacteria (PAB) was followed. The usual cooking step in the cheese process (up to 50 o C and 30 min) inactivated the lipoprotein lipase (EC 3.1.1.34) and the main factor in the lipolysis of Emmental cheese was shown to be the lipolytic activity of PAB. This activity was strain-dependent and not related to the production of propionic acid in cheese. The most abundant FFAs were palmitic acid, oleic acid, myristic acid and stearic acid as in milk fat and it was concluded that lipolytic activity of PAB is non-specific. Lastly, an interaction still not elucidated was evidenced between certain PAB strains and thermophilic lactobacilli strains regarding lipolysis extent in Emmental cheese. propionic acid bacteria / lipolysis / free fatty acid / Emmental cheese

Indirect conductimetry in the study of propionibacteria inhibition

Temperature (T), pH and NaCl concentration are the parameters that control the rate of propionic acid bacteria (PAB) growth. The indirect conductimetric technique was employed and a medium containing yeast extract, Na acetate, L (+)-cysteine chloride and Na lactate was formulated to amplify the electric signal. Sixteen PAB strains isolated from milk for Grana cheesemaking were tested in different combinations of 4 parameters (temperature, pH, NaCl and species); data were expressed as percentage of growth delay compared to standard conditions (pH 6.1, 30 °C, no NaCl added). Decreasing temperature caused the most significant growth delay (131% at 22 °C and 438% at 15 °C), while PAB growth with decreasing pH and increasing NaCl concentration was less affected in the most restrictive conditions (236% at pH 5.2 and 222% at 2.5% NaCl respectively). A slight stim- ulating effect was observed at 30 °C and low NaCl content (from 193% at 0% down to 187% at 0.5%). The double combinations T 〈 pH and T 〈 NaCl further increased delay values up to 489% (T 〈 pH) and to 482% (T 〈 NaCl) in the most restrictive conditions, and temperature was always the most important factor; the stimulating effect due to NaCl was amplified at 30 °C for all concentrations and at 22 °C at 0.5%. A significant difference was found in the behaviour of the 4 tested species: P. thoeni was the most inhibited, while P. freudenreichii and P. acidipropionici underwent the low- est growth reduction. Strictly controlled temperature (under 22 °C), curd acidification (under pH 5.4) and brine salt concentration are the cheesemaking steps identified as the critical points for con- taining PAB growth; the reliability of the proposed method suggests further individualization of the most suitable factor levels to contain the late blowing defect. Propionibacterium / inhibition / indirect conductimetry

Potential antimutagenic effect of the milk protein casein in the E. coli DNA-repair liquid suspension and DNA-repair host-mediated assay

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.

Propionibacteria in Italian hard cheeses

Summary - Economie losses for Parmigiano Reggiano and Grana Padano, for which production is about 200 000 tons per year, can result from Iate blowing caused by propionic acid bacteria (PAB). PAB contents of 306 milk samples for Grana cheese were analyzed. The mean value was 726 du/ml; however, when the 8 samples with the highest PAB content (>5 000 du/ml) are not included, this mean decreases to 377 du/ml. Sixty strains of PAB were isolated, identified (65% P freudenreichii, 25% P jensenii, 5% P thoenii and 5% P acidipropionici) and tested under different incubation temperatures (30, 22, 15°C), pH of the substrates (6.0, 5.5, 5.0) and concentrations of NaCI (0.5, 1.0, 1.5, 2.0, 2.5, 3.0%). The optimal condition was 30°C, with considerable slowing of the growth at lower temperature. ln the presence of NaCl, as the incubation temperature decreased, the number of the totally inhibited strains increased, while the total of those insensitive and those only partially inhibited remained the sa me up to 1.5% of NaCI and increased at higher concentrations. The strains resulted partially or strongly inhibited only at pH 5.0, while the total number of insensitive strains and those only partially inhibited increased as the temperature was lowered. An extreme adaptability of PAB even to very drastic conditions was noted: anywhere combinations such as low temperature « 22°C), high salt concentrations (> 2%) and low pH values «5.5) could effectively delay their development during the ripening of Grana cheese without total inhibition.

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.