The effect of different concentrations of Zataria multiflora Boiss. essential oil (EO; 0%, 0.005%, and 0.015%), nisin (0, 0.125, and 0.25 microL/mL), and their combinations on the production of staphylococcal enterotoxin C (SEC) and alpha-hemolysin (alpha-toxin) by Staphylococcus aureus at different inoculation levels (10(3), 10(4), and 10(5) cfu/mL) in brain heart infusion broth during storage at 35 degrees C for up to 43 days was evaluated. The SEC production was significantly (p < 0.05) inhibited and the hemolysis due to alpha-toxin was significantly (p < 0.05) reduced by EO concentration at levels 0.015% and 0.005%, respectively. Significant (p < 0.05) inhibitory effect of EO on SEC production at level 0.005% was observed when it was used in combination with nisin = 0.125 microL/mL. The significant (p < 0.05) synergistic effect of EO = 0.005% and nisin = 0.125 microL/mL was also observed as more reduction of hemolysis due to alpha-toxin than EO = 0.005% alone. Further, EO significantly (p < 0.05) prevented SEC production by S. aureus during the manufacturing process of a traditional Iranian white brined cheese (as a food model) even at its lowest concentration (5 microL/100 mL), in this study.

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One of the most recent and effective methods, which is currently receiving special attention and is being developed by numerous researchers, is production of microspheres from the probiotic cells. The largest market segment for functional foods is represented by dairy products, which have been touted as the most effective carriers of nutrients, such as probiotics, prebiotics, proteins, vitamins, and minerals. Yogurt is fermented dairy product that is popular all over the world. A new functional symbiotic yogurt fabricated by plant wastes (carrot pomace extract), Lactobacillus plantarum, and beads based on Alyssum homolocarpum seed gum (AHSG) and sodium alginate (SA) using extrusion technique was produced and characterized. Evaluation of the functional properties of yogurts indicated that the total phenolic content and DPPH radical scavenging activity were in the range of 16.13–48.30 µg GAE/ml and 7.4–14.64%, respectively. The acidity, pH, syneresis, water holding capacity, lightness, redness, and yellowness of the yogurts were in the range of 1.50–2.90, 4.07–4.38, 49.00–57.24%, 46.8–57.3%, 57.16–61.25, − 0.20–0.91, 6.40–13.06 on the 28th day storage, respectively. The panelists confirmed the sensory properties of yogurt samples. Probiotic survival rate of the functional yogurts were in the range of 6.37–8.13 log CFU/g, on the 28th day. Based on the results, bead production by AHSG and SA and the use of carrot pomace extract enhanced the survival of probiotic bacteria significantly in yogurt during storage compared to free cells. Graphical Abstract

This study was designed to evaluate the chemical constituents of Zataria multiflora Boiss. essential oil (EO) and its inhibitory effect on enterotoxin type C production by Staphylococcus aureus ATCC 6538. Moreover, the effect of this EO on gene expression of staphylococcal enterotoxin type C (SEC) was assessed. The effect of different concentrations of EO on enterotoxin C production was evaluated using 3-enzyme-linked immunosorbent assay. The reducing effect of EO subinhibitory concentrations on gene expression of enterotoxin was assayed using real-time polymerase chain reaction as well. EO at the level of 0.005% had no inhibitory effect on enterotoxin C production, and by increasing the subinhibitory concentration of the EO to 0.015%, an inhibitory effect was observed. Comparing the relative gene expression of SEC in control and treatment groups showed that the EO concentrations of 0.0075 and 0.015% had a significant downregulation (10.7 and 23.8 times, respectively) of sec gene. PRACTICAL APPLICATIONSThis research raises important implications for the potential use of Zataria multiflora Boiss. essential oil as a natural preservative and a new approach for biocontrol of Staphylococcus aureus. Besides, it can provide additional knowledge of the mechanisms involved in EO against S. aureus intoxication based on gene expression and open new avenues for the biocontrol of this microorganism in food industry and/or the extension of the shelf life of processed foods.

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Journal homepage: www.zums.ac.ir/jhehp Background: Identification of the dominant lactic acid bacteria involved in the production of traditional cheese in Semnan could be the initiative to protect national genetic resources and produce industrial cheese with desirable texture and organoleptic characteristics similar to traditional cheeses. The present study aimed to determine the biochemical, physiological, and phenotypic properties of the dominant strains of the lactic acid bacteria (LAB) isolated from the traditional cheese in Semnan, Iran using 16S rRNA gene sequence analysis. Methods: In total, 14 cheese samples were randomly collected from the northern countryside of Semnan, Iran. The isolated gram-positive and catalase-negative colonies were analyzed in terms of morphology, culture, physiology, biochemical properties, and carbohydrate fermentation pattern. Following that, the LAB isolates were identified based on 16S rRNA gene sequence analysis, and a phylogenetic tree was drawn for the bacterial strains. Results: In this study, 105 isolates were determined, 58 of which (55.24%) belonged to the genus Lactobacilli, and 47 isolates (44.76%) belonged to the genus Enterococci. According to the biochemical tests and 16S rDNA sequencing, the identified dominant Lactobacillus species included L. plantarum (53.6%), L. paracasei (32.7%), and L. casei (13.7%). In addition, most of the Enterococcus species were E. faecium (74.47%) and E. durans (25.53%). Conclusion: According to the results, exploring the microbiological diversity of traditional cheese could contribute to the selection of proper bacterial strains for the manufacturing of products with consistent quality and original taste on an industrial scale.

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