The Inhibitory Effects of 2 Commercial Probiotic Strains on the Growth of Staphylococcus aureus and Gene Expression of Enterotoxin A

Background: Food-borne intoxications are current problems in human society and most of them are caused by the enterotoxins of Staphylococcus aureus. Staphylococcal enterotoxin A (SEA) is the most frequently responsible for staphylococcal food poisoning outbreaks. From a food safety and human health point of view, lactic acid bacteria (LAB) may provide a promising strategy to combat the pathogenic bacteria, particularly S. aureus. Objective: The objective of this study was to evaluate the inhibitory activity of two commercial lactobacillus strains on growth and enterotoxin A production by S. aureus. Moreover, the inhibitory effect of these strains on gene expression of enterotoxin type A was assessed using real-time Polymerase chain reaction (PCR). Materials and Methods: In this study the inhibitory effect of two commercial probiotic strains, Lactobacillus acidophilus (LA5) and Lactobacillus casei 01 on the growth and enterotoxin production of S. aureus was evaluated at 25 and 35°C. The gene expression of SEA of S. aureus was also evaluated by real time (RT) PCR technique. Results: The lactobacillus strains decreased the bacterial count at both temperatures compared with the control group. This reduced effect was greater at 25°C (3 log/CFU) than 35°C (2 log/CFU). The production of SEA, SEC and SEE was inhibited by the lactobacillus strains. Furthermore, the gene expression of SEA was significantly suppressed in S. aureus co cultured with studied lactobacillus strains and the greatest down-regulation of sea (10.31 fold) was observed in co-incubation of S. aureus with LC01 at 25°C. Conclusion: This research raises important implications for the potential use of LAB as a natural preservative in foodstuffs by correct microbial ecology of the environment and a new approach for biocontrol of S. aureus

Application of carrot waste extract and Lactobacillus plantarum in Alyssum homalocarpum seed gum-alginate beads to create a functional synbiotic yogurt

Abstract 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 Abstrac