مجله میکروبیولوژی کاربردی در صنایع غذایی
سال هشتم شماره 2 (تابستان 1401)

Yogurt production by milk fermentation is one of the oldest methods used by humans to convert milk into a product with longer shelf life and better sensory evaluation. This study aimed to investigate the characteristics of lactic acid bacteria isolated from yogurt in Zanjan rural areas and these strains ability in the diacetyl production. This study collected and transferred seven yogurt samples to the laboratory under standard conditions. Then the isolated strains were examined for morphology, several test such as catalase, hemolysis, antibiotic susceptibility, growth rate at different temperatures and yogurt sensory evaluation. The selected yogurt samples were examined for diacetyl production using SPME-GC after bwing stored at 5°C for 14 days. According to the results, the strains were divided into two groups based on morphology: bacilli and cocci. All strains were gram-positive and catalase negative. Most of the studied strains were antibiotic sensitive and shown negetive hemolysis. In the selected yogurt samples L1and N7, the diacetyl production was 5/6,10ppm respectively. The studied strains had high diacetyl production ability and also caused the butter aroma and the traditional Iranian yogurt memory, which leads to the production of yogurts that is more compatible with the Iranian people’s taste.

Probiotics are living microorganisms that, when consumed in sufficient quantities, have beneficial effects on the host, and their excellent characteristic is that they are safe, secure, and have antioxidant activity for the host. The aim of this study was to investigate the effect of a mixture of native Iranian probiotics (Lactobacillus rhamnosus, Lactobacillus helveticus, and Lactobacillus casei) on lung tissue changes in male rats infected with lead acetate. In this experimental study, 21 male Wistar rats were divided into 3 groups of 7: control, lead acetate, lead acetate + mixture of native Iranian probiotics. A single dose of lead acetate injection (10 mg/kg) was done intraperitoneally and probiotics (109 CFU/ml) were gavage for 35 days. After the end of the experiment, the rats were anesthetized, then tissue sections were prepared from the lungs, the samples were stained with hematoxylin-eosin and photographed and studied by a light microscope. The study of morphological changes in lung tissue in the group treated with probiotics showed a reduction in tissue damage compared to the lead acetate group. According to the findings of this study, the use of a mixture of native Iranian probiotics (Lactobacillus rhamnosus, Lactobacillus helveticus, and Lactobacillus casei) can improve the induced damage of lead acetate in lung tissue.

Akkermansia muciniphila, an important member of the gastrointestinal microbiota, is involved in the functioning of the host immune system. We aimed to investigate the effect of A. muciniphila and its OMVs on the expression of microRNA-21 and microRNA-34a involved in the maturation of human dendritic cells. A. muciniphila was cultured on a mucin-containing medium and its OMVs were extracted by ultracentrifugation. Extraction of peripheral blood mononuclear cells (PBMCs) was performed using Ficoll’s density gradient centrifugation method. Monocytes were differentiated into dendritic cells in the presence of interleukin-4 cytokines and granulocyte-monocyte colony-stimulating factor. Then, A. muciniphila at MOI 50 and 100, OMVs at a dose of 50 µg/µl, dexamethasone (to induce tolerogenic dendritic cells), and the LPS (to induce mature dendritic cells) were incubated. Finally, the expression of microRNA-21 and microRNA-34a was measured by real-time PCR. The morphological characteristics of the extracted OMVs showed that their size was between 20-200 nm. In LPS treatment, there were longer cytoplasmic growths than OMVs of dexamethasone and A. muciniphila groups. MicroRNA-21 expression was decreased in the LPS group compared to dexamethasone, A. muciniphila, and OMV groups, although this decrease was not significant (P> 0.05). In addition, microRNA-34a expression was significantly increased in the LPS group, which was reversed by treatment with dexamethasone, A. muciniphila, and OMV (P <0.001). MicroRNA-21 and microRNA-34a can exhibit anti-inflammatory and pro-inflammatory functions. A. muciniphila and its OMVs appear to be a viable option for introduction as a new generation probiotic.

Cheese is a dynamic dairy product that goes through extensive biochemical and microbial changes as it ripens. The growth of molds, such as Penicillium and Aspergillus, has long been an issue for producers during the processing and ripening process. The aim of this study was to evaluate the antimicrobial properties of cumin essential oil in the manufacturing of lactic cheese, as well as investigation of the effect of essential oil on the survival of lactic acid bacteria in cheese. For this purpose, concentrations of 200, 500 and 1000 mg/L of cumin essential oil were added to lactic cheese samples and the total population of bacteria, mold and yeast, lactobacilli and lactic streptococci were counted and the direct growth of Aspergillus flavous and Penicillium citrinum on pieces of cheese was studied in the first, 15th, 30th and 60th days of refrigerated cheese. Also, the impact of effect of essential oil on the sensory properties of the samples was investigated. The results revealed that with the population of all microbial groups rises as storage time increases, but this tendency is slower in samples containing essential oils and this inhibitory effect is directly related to increasing the concentration of essential oils. Furthermore, the synergistic effects of cumin essential oil and lactic acid bacteria in the control of microorganisms were also demonstrated. Cumin essential oil did not inhibit the growth of lactic acid bacteria in cheese samples and even encouraged their growth by reducing the number of competing microbes. Considering the general acceptance of the sensory properties of the samples, the use of 500 mg/L cumin essential oil is recommended, especially to control the growth of Aspergillus and Penicillium molds in Lactic cheese.

In this study, turkey breast meat was thawed by using the immersion ohmic method in three different treatments (66V, brine concentration 0.186% W/V), (120 V, brine concentration 0.186% W/V) and (120 V, brine concentration 0.25% W/V). The effect of this method on the growth rate of mesophilic and psychrophilic bacteria after thawing, were compared with traditional methods of thawing; Air (25°C) and water (40°C). Thawing time for air, water, ohmic (66 V, brine concentration 0.186% W/V), ohmic (120 V, brine concentration 0.186% W/V), and ohmic (120 V, brine concentration 0.25% W/V); 398 S, 107 S, 113 S, 97 S and 91 S were obtained, respectively, which indicated a significant decrease in the thawing time using the ohmic method compared to the traditional thawing methods. Also, with the increase in voltage, the thawing time to reach the set temperature decreased, but the effect of increasing brine concentration on the decrease of thawing time was insignificant. The results showed a significant reduction in the thawing time using the ohmic method. The results of analysis of variance of a completely random design indicated that the effect of different thawing treatments on the growth of mesophilic and psychrophilic bacteria was significant at the probability level of 1%. In the results of the mean comparison test between different treatments, a significant difference was observed at the five percent probability level. In ohmic thawing, with increasing voltage and brine concentration, the growth rate of bacteria was significantly reduced compared to other treatments. The lowest survival rates of mesophilic bacteria and psychrophilic bacteria, and also the shortest thawing time was observed in ohmic treatment of 120 volts in brine concentration of 0.25% W/V.

Escherichia coli  induced urinary tract infection urinary tract infections is a prevalent acquired infection in Iran. The papG virulence gene plays a crucial role in the pathogenesis of E. coli, particularly in binding to epithelial cells.  In addition, as a group of probiotics, lactobacilli have an important role in the body and are therapeutically benefits in some cases. This study aimes to molecularly investigate the effect of Lactobacillus casei PTCC 1608 on different strains of uropathogenic E. coli  isolated from urinary infection through PCR. The desired strain of E. coli was isolated from patients with urinary tract infections and investigated through differentiation methods. The papG gene of the desired strain was evaluated through PCR and then strains with positive genotypes were isolated and the antibacterial effect of Lactobacillus casei was evaluated through dilution and disc diffusion methods in a liquid medium. The antibacterial effect of Lactobacillus casei on antibiotic-resistant uropathogenic E. coli was studies. From a total of 40 samples isolated from the urine of patients with urinary tract infections, the results of MIC-MBC were either positive or negative. The antibiotic sensitivity test at the dilution of 1 to 10 showed an inhibition zone of 9 cm. These results indicated that the isolated bacterium was not resistant to ampicillin and the antibiotic did not lose its therapeutic effect. Moreover, the probiotic used has a therapeutic role and can improve urinary infections.