Iranian Food Science and Technology Research Journal

Abstract Introduction: Probiotics are viable microbial food supplements that, when well-arranged in adequate amounts, confer a health advantage on the host. Probiotics have different positive health impacts such as equilibration of intestinal microbiota, prevention of cancer and diarrhea, reduction of cholesterol and blood pressure, adaptation to lactose intolerance, improvement of immune system, decrease of allergic symptoms, inhibition of pathogenic microorganisms etc. Lactic acid bacteria (LAB), are the most common bacteria introduced as probiotics.
 
Materials and methods: In this research, a strain of Lactobacillus planetarium LZ95 was utilized and its probiotic potential was evaluated. This strain had been isolated from a traditional Iranian fermented food known as Ash-Kardeh and had been identified using culture-dependent methods and molecular techniques. Lactobacillus planetarium, is one of the known LAB bacteria. The aim of this study was to evaluate the probiotic potential of Lactobacillus plantarum LZ95 in relation to its resistance to acid (pH 2.5, 3.5 and 5.5), its ability to grow in different bile salt concentrations (0.2, 0.5, 0.8, 1.2 and 3%), its resistance against chloramphenicol, tetracycline, penicillin and gentamycin antibiotics, and its antimicrobial activity against Listeria innocua, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli by using “Lawn on the spot” method.
 
Results and discussion: Results shown that the viability of Lactobacillus plantarum ranged from 0 to 97.69 percent. The highest and the lowest bacteria viability were determined at pH=5 and 2, respectively. The results revealed that Lactobacillus plantarum was able to grow at all tested bile salt concentrations (0.2, 0.5, 0.8, 1.2 and 3%), and the lowest and the highest viability was found at 0.2 and 3 percent of bile salt levels, respectively. Lactobacillus plantarum was susceptible to all tested antibiotics. Results also shown that chloramphenicol with an inhibition zone diameter of 30.10 mm had the highest anticipation effect on the strain. Antimicrobial activity of Lactobacillus plantarum against Staphylococcus aureus (gram positive) and Escherichia coli (gram negative) with inhibition zone diameters of 11.30 and 7 mm was the highest and the lowest, respectively. The inhibition zone diameter around the strain of Lactobacillus plantarum revealed its ability to inhibit the growth of selected pathogenic bacteria. Based on results, the inhibition zone diameter against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Listeria innocua were 11.30, 7.00, 10.70, and 8.90 mm, respectively. In general, the isolated strain of Lactobacillus planetarium LZ95 had an acceptable probiotic potential such as resistance to bile salt and acidic conditions, susceptibility to some commonly antibiotics, and appropriate antimicrobial activity against food pathogenic bacteria. Therefore, this strain can be used in food industry to produce functional food products.

Abstract Introduction: Probiotics are live microorganisms, if consumed in enough quantity, they exert beneficial effects on human health owing to improvement of intestinal microbiota balance. In addition to the impact on gut microbiota, probiotics have important role on human physical and mental health. This matter demonstrates the increasing emphasis on the consumption of diet based on probiotics in order to treat and prevent of different chronic diseases, particularly those related to stress and inflammation cases. Lactic acid bacteria (LAB) are the most common strains used as probiotics. They are useful member of gut microbiota and belong to generally regarded as safe (GRAS) microorganisms. Because of the numerous benefits of LAB, the probiotic potential of different strains of this group of bacteria has been assessed broadly. Although various commercial species of probiotics are available in the market, determination of new strains with individual properties is noteworthy. Therefore, this research was aimed to investigate the probiotic and antimicrobial potential of Lactobacillus fermentum isolated from fermented food.
 
Materials and methods: In the study,the probiotic potential of Lactobacillus fermentum including its resistance to acid (pH 2.5, 3.5 and 5.5) and bile salts (0.2, 0.5, 0.8, 1.2 and 3%) was studied. To evaluate the bile salts resistance, 100 μl of prepared microbial suspension was cultured on MRS Agar media containing bile salts. Plates were incubated at 37 ᵒC for 24 hrs under anaerobic condition. After incubation period, the plates were inspected for bacterial colonies observed by naked eyes. The antimicrobial activity was measured using “Lawn on the spot” method against Listeria innocua, Staphylococcus aureus and Pseudomonas aeruginosa. The resistance of Lactobacillus fermentum was also assessed against commonly used antibiotic drugs (chloramphenicol, tetracycline, penicillin and gentamycin).
 
Results and discussions: Results shown that although Lactobacillus fermentum was not able to grow at pH 2.5, its viability in the pH 3.5 and 5.5 was 92 and 99%, respectively. This strain had also adequate resistance against different bile salt concentrations. In the present research, the growth rate of the examined strains was gradually reduced as the bile salt concentration was increased; so that  the higher and the lower growth rate was observed at 0.2 and 3% bile salt concentrations, respectively. Results shown that the tested Lactobacillus fermentum had acceptable bacteriostatic effect on the selected pathogenic bacteria. The inhibition zone diameter for Listeria innocua, Staphylococcus aureus and Pseudomonas aeruginosa was 12.6, 20 and 11.1 mm, respectively. The maximum diameter of inhibition zone was found on gram positive Staphylococcus aureus. Lactobacillus fermentum was susceptible to chloramphenicol, tetracycline and penicillin and was semi-resistant to gentamycin (comparison with table CLSI).
Based on the obtained results in this study, it may be illustrated that Lactobacillus fermentum had capability to tolerate the lower pH and different bile salt concentrations. This strain showed the proper proficiency to inhibit pathogenic bacteria. Furthermore, it was susceptible to commonly used antibiotic drugs and therefore there is no concern about the transfer of antibiotic resistant gens into pathogenic bacteria. Consequently, this strain may be used as a probiotic and a natural preservative in production of functional food products.