Search

Today, various sterilization methods are used for the removal of microorganisms, some of which are based on thermal methods that have negative effects on the physicochemical properties of milk. The present study aimed to investigate the effects of cold plasma at atmospheric pressure on the population of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in raw milk. Initially, a plasma jet filled with argon gas was used to evaluate the antibacterial effects of cold plasma. Following that, pasteurized milk samples (1.5% and 3% fat) were infected with standard strains of E. coli and coagulase-positive S. aureus and irradiated with cold plasma at the frequency of 22, 28, and 33 kHz and voltage of 20, 12.5, and 10 kV for five minutes. The results of statistical analysis and Tukey's test indicated that the E. coli and S. aureus microbial load was significantly lower in the 1.5% fat milk compared to the control group (P<0.05). In addition, the milk samples exposed to plasma at 20 kV and 28 kHz showed the most significant reduction in the number of E. coli bacteria compared to the control samples (P<0.05). The milk samples exposed to 10 kV and 33 kHz also showed the most significant reduction in the S. aureus microbial load. According to the results, cold plasma could decrease the microbial load of milk containing 1.5% fat more significantly compared to the 3% fat milk. Therefore, plasma could be a proper alternative to thermal decontamination methods for raw milk. However, its application requires further studies to determine the intensity and duration of the exposure of microorganisms to cold plasma at atmospheric pressure. [ABSTRACT FROM AUTHOR]

High levels of nitrate and nitrite in groundwater lead into environmental issues and nitrate poisoning causes unpleasant consequences in human bodies. The present study was conducted to evaluate the concentration of nitrate, nitrite, and nitrate-reducing bacteria in treated drinking water in five areas in Tehran using optical spectroscopy. The results of one-way ANOVA showed that the average concentrations of nitrate in summer and autumn are significantly higher than those of nitrite. Moreover, the highest mean of concentration of nitrate and nitrate was observed in the west of Tehran in autumn 2016 (1.2±0.01 and 4.6±0.02 mg L-1). On the other hand, the lowest mean was found in the south of Tehran (0.06±0.02 and 0.001±0.01 mg L-1). However, only in the southern region of Tehran, signs of Pasteurella sp. and Acinetobacter sp. were observed. Additionally, the results of the Duncan test indicated no significant differences concerning nitrate concentration in the morning, noon, and at night in the southern, eastern, and central regions in autumn and summer. The samples of the north, east, and center had the lowest risk and, in the west, and south of Tehran, the highest risk and adverse effects of nitrite and nitrate were observed. Although the average concentration of nitrate and nitrite in all these areas, except for the west of Tehran, was less than the standard of the WHO and the latest national standard, protection of groundwater resources against the entry of pollutants treatment networks to prevent the increase of these ions in water seems to be necessary. [ABSTRACT FROM AUTHOR]

Abstract: This study investigated the ability of Bifidobacterium animalis lactis and Lactobacillus delbrueckii bulgaricus at concentrations of 108 and 109 cfu/ml to detoxify skim milk that was contaminated with 0.25 ng/ml, 0.5 mg/ml, and 0.75 mg/ml aflatoxin M1 (AFM1) at 30 min, 60 min, 120 min, and 24 hr, and at 4 and 37 °C. The maximum level of AFM1 binding to 1 × 108 cfu/ml of L. bulgaricus was 57.5 ± 5.2% at 37 °C. Both strains showed the degrading potential to reduce AFM1 concentrations and, thus, could be used as starter cultures to detoxify milk. Furthermore, the temperature, bacteria concentration, and vitality have more significant influence on AFM1 binding in contaminated milk than other indices. The results indicated that Bifidobacterium lactis and Lactobacillus bulgaricus could be used as beneficial probiotics to decrease the destructive properties of AFM1 to consumers exposed to AFM1‐contaminated milk. Practical applications: The upcoming demands are to embrace probiotic strains that have documented beneficial health effects for the consumer. Bifidobacterium animalis lactis and Lactobacillus delbrueckii bulgaricus can be used as probiotic to bind selected dietary contaminants particularly AFM1 in milk by binding the toxin or enzymatic detoxification. The optimum results will be gained while the probiotic will be added to the milk at 4 °C and early stage of the exposure especially at 30 min. [ABSTRACT FROM AUTHOR]

Background: The occurrence of aflatoxins in food products is a silent threat to human health worldwide. A range of strategies has been introduced to address the bioavailability of aflatoxins, which are considered microbial tools to provide a low-cost and promising approach., Objectives: The present study focused on the separation of yeast strains from the homemade cheese rind layer to investigate the ability of native yeasts to eliminate AB1 and AM1 from simulated gastrointestinal fluids., Material and Methods: Homemade cheese samples were prepared from different locations in Tehran provinces and yeast strains were isolated and identified through the biochemical methods and molecular analysis of internal transcribed spacer and D1/D2 domain of 26S rDNA regions. Isolated strains were screened using simulated gastrointestinal fluids, and the ability of yeast strains to absorb aflatoxin was evaluated., Results: Out of 13 strains, 7 yeast strains were not affected by 5 ppm AFM1 while 11 strains did not show any significant response to 5 mg.L -1 (ppm) of AFB1. On the other hand, 5 strains were able to successfully tolerate 20 ppm AFB1. Candidate yeasts showed different abilities to remove aflatoxins B1 and M1. In addition, C. lusitaniae , G. geotrichum , G. candidum , and C. sanyaensis exhibited a significant ability to detoxify aflatoxins from the gastrointestinal fluid, respectively., Conclusion: Our data suggest that yeast communities with essential effects on the quality of homemade cheese appear to be precise candidates for the potential elimination of aflatoxins from the gastrointestinal fluid., (Copyright: © 2021 The Author(s); Published by Iranian Journal of Biotechnology.)