Objective:Probiotics such as lactobacilli prevent the development of a wide range of human and animal's pathogens. The aim of this study was evaluation of antagonistic effect of isolated lactobacilli from local dairy products against three standard strains of Staphylococcus aureus, Bacillus subtilis, and Pseudomonas aeruginosa.Materials and Methods:Twenty samples of local dairy products including cow milk, buffalo milk, cheese, and yogurt were collected from different areas of Ahwaz city. Antimicrobial disc diffusion method was applied on S. aureus (ATCC-6538), B. subtilis (ATCC-12711), and P. aeruginosa (ATCC-27853). Antimicrobial effects of isolates were evaluated by disc diffusion test on Mueller-Hinton agar medium plated with three pathogens.Results:Obtained results showed that only three strains of isolated lactobacilli of local dairy samples had inhibitory effects on understudy pathogens including Lactobacillus alimentarius, Lactobacillus sake, and Lactobacillus collinoides. All three isolates showed moderate activity (inhibition zone <15 mm) except of L. collinoides and L. alimentarius that had relatively strong activity (inhibition zone ≥15 mm) against P. aeruginosa and B. subtilis, respectively.Conclusion:These bacteria can be raised for the production of various kinds of food, pharmaceutical products, and functional foods.

Objective:The Lactobacillus is a genus of lactic acid bacteria which are regularly rod-shaped, nonspore, Gram-positive, heterogeneous, and are found in a wide range of inhabitants such as dairy products, plants, and gastrointestinal tract. A variety of antimicrobial compounds and molecules such as bacteriocin are produced by these useful bacteria to inhibit the growth of pathogenic microbes in the food products. This paper aims to examine the isolation of Lactobacillus from local dairies as well as to determine their inhibition effect against a number of pathogens, such as two fungi: Penicillium notatum and Aspergillus fulvous.Materials and Methods:Twelve Lactobacillus isolates from several local dairies. After initial dilution (10−1–10−3) and culture on the setting, de Man, Rogosa and Sharpe-agar, the isolates were recognized and separated by phenotypic characteristics and biochemical; then their antifungal effect was examined by two methods.Results:Having separated eight Lactobacillus isolates, about 70% of the isolates have shown the inhabiting areas of antifungus on the agar-based setting, but two species Lactobacillus alimentarius and Lactobacillus delbrueckii have indicated a significant antifungal effect against P. notatum and A. fulvous. Except bacteriocin, lactic acid, and acetic acid, the inhibitor substance is produced by these bacteria.Conclusion:Given the vitality of Lactobacillus in human health, recognition and isolation of the species producing compound in antagonist to the pathogens existing in the food products can be a helpful and effective step toward maintaining the valuable native Lactobacillus and using them in the dairy industries.

Background: Spirulina is one of the most profitable known microalgae in the world, which is used as food and superfood. In the other hand, Spirulina is a useful source of healthy components. It seems that the Spirulina is transformable so that the introduction of a selectable marker is needed. Objectives: The purpose of this study was to determine a suitable selection marker for Spirulina platensis. Thus, this experiment was designed to survey the response of Spirulina to different concentrations of candidate antibiotics including kanamycin, hygromycin, phosphinothricin, chloramphenicol and streptomycin in standard Zarrouk medium. Materials and Methods: S. platensis culture matched to 1 McFarland standard and its resistance to different antibiotics was studied by serial dilution of kanamycin, hygromycin, phosphinothricin, chloramphenicol and streptomycin. Biomass was detected after 7days using spectrophotometer and related growth graphs were illustrated. Results: Fresh culture of S. platensis reached to exponential phase on day 4 of experiment. While this phase was presented on day 5 for cultures containing kanamycin or hygromycin. The Spirulina cultured in medium supplied with basta, did not reach to growth phase however, chloramphenicol can stop the growth of Spirulina cells. Spirulina showed resistance to streptomycin with the concentration of 40 mg/L and higher. Therefore, streptomycin can use as selectable marker to detect GM (Genetic Modified) Spirulina spp. Conclusions:The streptomycin can be used as suitable selection marker in comparison with other introduced markers. For using this selectable marker, integration of a streptomycin resistant gene is needed. The gene aadA is a potential candidate. The aadA gene can be expressed under the control of upstream and downstream elements of S. platensis.