In the present study, the inhibitory effect of nisin-producing Lactococcus lactis during co-culture and pure standard nisin were assessed against selected foodborne pathogenes in growth medium and Iranian UF Feta cheese. In comparison L lactis, not only proves flavor but also plays a better role in microbial quality of Iranian UF Feta cheese as a model of fermented dairy products. L. lactis subsp. lactis as nisin producer strain, Listeria monocytogenes, Escherichia coli and Staphylococcus aureus as pathogenic strains were inoculated in Ultra-Filtered Feta cheese. Growth curve of bacterial strains were studied by colony count method in growth medium and UF Feta cheese separately and during co-culture with L. lactis. Nisin production was determined by agar diffusion assay method against susceptible test strain and confirmed by RP-HPLC analysis method. Counts of L. monocytogenes decreased in cheese sample containing L. lactis and standard nisin, to 103 CFU/g after 7 days and it reached to undetectable level within 2 weeks. S. aureus counts remained at its initial number, 105 CFU/g, after 7 days then decreased to 104 CFU/g on day 14 and it was not detectable on day 28. E. coli numbers increased in both treatments after 7 days and then decreased to 104 CFU/g after 28 days. Despite the increasing number of E. coli in growth medium containing nisin, due to the synergistic effect of nisin and other metabolites produced by Lactococcus lactis and starter cultures, the number of E. coli decreased with slow rate. Discussion and The results showed, L. monocytogenes was inhibited by L. lactis before entering the logarithmic phase during co-culture. S. aureus was also inhibited during co-culture, but it showed less sensitivity in comparison with L. monocytogenes. However, the number of E. coli remained steady in co-culture with L. lactis. Also, we found that, in all cheese samples, E. coli decreased slowly after 28 days which may be due to the synergistic inhibitory effects of nisin and other metabolites produced by L. lactis and starter culture strains. These conditions are compatible to UF Feta cheese making processes. The usage of L. lactis is more effective in terms of pathogenic inhibitory in comparison with free nisin. Using L. lactis as an adjunct starter culture can assist microbial quality improvement and prevent important pathogens, which may survive during food processing, because of the production of beneficial metabolites.

Background and Dairy products often associated with problems such as short shelf life and poor hygiene control. A novel approach is to utilize bacteriocin or bacteriocin producer strains, to control undesirable micro flora as Listeria monocytogenes and Bacillus cereus in foods. Hence, we studied the effect of nisin like producing Lactococcus lactis against Listeria monocytogenes and Bacillus cereus, in order to compare the isolated strain within different countries. In this research we studied the effect of nisin like producing Lactococcus lactis, with producer spot test method. We also used supernatant from 24 h culture of Lactoccus lactis. Moreover, we studied the effect of bacteriocin on Listeria monocytogenes and Bacillus cereus growth curves. The growth of both strains was inhibited by the bacteriocin. According to our results, the bacteriocin could be used in liquid food with bacteriocin added directly or as a starter culture in fermentation. This would inhibit the growth of Listeria monocytogenes furthermore, Bacillus cereus is used to reduce food poisoning for fermented food products.

Nisin is a biological bacteriocin with many functions against food pathogenic bacteria. The disadvantages of chemical preservatives in foods have attracted attention to natural preservatives such as nisin. This study evaluated the antimicrobial properties of nisin extracted from Lactococcus lactis isolated from goat milk. Ten goat milk samples were collected from around Kerman city under sterile conditions, and Lactococcus lactis were isolated in the selected environment of Eliker-trimethoprim. Biochemical tests were used to Strain identification and nisin gene confirm by polymerase chain reaction with specific primers was used. HPLC method was used to confirm the presence of nisin using bacterially extracted proteins. The antibacterial properties of nisin were performed by disk diffusion agar method against Staphylococcus aureus, Bacillus cereus, Acinetobacter baumannii, and Pseudomonas aeruginosa. The minimum inhibitory concentration of bacteriocin was performed by Provide serial dilution in a microtiter plate. One of the four strains of Lactococcus lactis was identified and selected with the best growth conditions for further investigation. The presence of the nisin gene in Lactococcus lactis was confirmed by a specific primer and polymerase chain reaction method. The amount of nisin produced protein was 41.5 mg/kg. The diameter of inhibitory zone for Staphylococcus aureus, Bacillus cereus, Acinetobacter baumannii, and Pseudomonas aeruginosa were 13, 17, 14, and 0, respectively, and minimum inhibitory concentrations for extracted nisin were in dilutions of 10-5, 10-6, 10-5 and 10-1, respectively. Therefore, nisin extracted from Lactococcus lactis in goat milk can be a suitable substitute for chemical preservatives.

This is a study aimed to investigate the effect of lactic acid bacteria including Lactobacillus acidophilus and Sterptococcus thermophilus (as thermophilic culture), Lactococcus lactis subsp. lactis, cremoris and diacetylactis, Leuconostoc citrovorum (as mesophilic culture), Lactobacillus acidophilus, Lactobacillus casei, Bifidobacterium lactis and a mixed culture of L.acidophilus, L. casei and B. lactis on fatty acid profile, conjugated linoleic acid (CLA) and atherogenic index (AI) of butter. Fatty acid analysis with gas chromatography indicated that application of thermophilic and mixed culture decreased the ratio of saturated to unsaturated fatty acid; whereas, the butters made with L. acidophilus had the highest content of CLA. Moreover, AI in the samples prepared with thermophilic cultures was the least. Sensory evaluation of the treatments revealed no significant differences (p> 0/05) in appearance and color. However, the butters prepared with thermophilic and mesophilic cultures had more desirable taste in comparison with the samples made with L. acidophilus, L. casei and B. lactis. From the nutritional point of view, the adverse effect of butter could be diminished via the application of selected lactic acid bacteria.

Phytic acid is a main compound in all plant seeds and contains 60 to 70% of total phosphorus in plant. Monogastric animals cannot use phytatephosphorus because of low phytase activity in their digestive tract. Thus in addition to unabsorbed mineral phosphorus, phytate phosphorus in fecal ofmonogastric animals may affect water and environment pollution. It is suggested to use of phytase enzyme for resolving of this problem. Phytase activity was showed in some bacteria like pseudomonas, bacillus subtilis and amyloliquefaciens. Few strain of lactic acid bacteria order showed phytase activity or were different for this activity. On the other hand these bacteria order are important as probiotic strains. There are numerous studies to use probiotic bacteria with specific enzyme activity for increasing nutrient availability to animals. This experiment was aimed to study of a recombinant Lactococcuslactis performance to degrade of phytate phosphorus in broiler chicken diets.
Lactococcuslactis was supplemented to a phosphorus deficient diet (50% of available phosphorus recommended by NRC) lonely or with two other lactobacillus bacteria (lactobacillus crispatusand lactobacillus salivarus) in rate of 108 CFU/g diet. Diets were also formulated with recommended available phosphorus by NRC with or without probiotic supplementation. Two hundred eighty eight one day old male Ross broiler chicks were subjected to 6 experimental treatment in 4 replicates and 12 chicks in each replicate. Growth performance, bone characteristics, intestinalmicroflora, and blood metabolites were measured. Apparent phytate digestibility was estimated by chromic oxide marker method. The chromic oxide was added in rate of 0.3% ofthediets. Phytate phosphorus was measured by the method of wheeler et al (1971). On day37, level of calcium, phosphorus and cholesterol of serum were measurement by bleeding from wing vein. Left thigh bone was isolated on 42 days and its dimensions and strength were measurement by Caliper and Instron instruments respectively.
Body weights of deficiency phosphorus treatments showed significant decrease evenin presence of recombinant probiotic (P Based on this study, it is suggested to develop of phytase gene expression in Lactococcuslactisby supplemental study and use of probiotic lactobacilli as same time.

In this study, milk fermentation capability by 6 isolates of lactic acid bacteria, proteolytic activity of lactic acid bacteria in milkby ortho-phthaldialdehyde (OPA)reagentand antifungal property of lactic acid bacteria in MRS broth and skim milk against Aspergillus flavus and Candida albicanswere studied. L. brevis KMJC1, L. acidipiscis KMJC2, L. curvatus KMJC3 and L. plantarum KMJC4 isolated from Jug cheese, L. helveticus KMCH1 isolated from camel doogh (Chal) and Lac. lactis KMCM3 isolated from camel milk were used. The results showed thatamong the isolates,L. plantarum KMJC4after 48 h, Lac. lactis KMCM3 after 16 hand L. helveticus KMCH1 after 60 hhad milk fermentation capability. The measurement of proteolysis rate performed infermented milk by mentioned isolates using OPA reagent indicated that the proteolytic activity of L. helveticus KMCH1, Lac. lactis KMCM3 and L. plantarum KMJC4 were 0.34, 0.26 and 0.22 mg/ml, respectively. In study of the antifungal effect of supernatant resulting from the activity of lactic isolates, it was found that supernatant obtained from culture in MRS broth had a more inhibitory effect (MIC= 25 and 50 mg/ml) than the supernatant obtained from the culture in the skim milk, as the MIC was not observed for the supernatant obtained from fermented milk. In the end, it can be concluded that Lac. lactis KMCM3 was able to ferment lactose in milk in comparisonwith other isolates in shorter time (16 h). The highest proteolytic activity of the isolates in milk was related to the isolate of L. helveticus KMCH1 (0.34 mg/ml). L. plantarum KMJC4 isolated from Jug cheese was as the best isolate for the preparation of supernatant resulting from MRS broth with the antifungal property.

In this study, acidification and proteolysis in reconstituted skim milk fermented using proteolytic lactic acid bacteria were investigated during fermentation and after 7 days of cold storage. Also, antibacterial activities of crude peptide extracts obtained from the fermented samples were evaluated. Lactobacillus delberueckii subsp. bulgaricusL. reuteri and Lactococcus lactis subsp. lactis were used as starter in single or co-culture. Lactococcus lactis subsp. lactis and lactobacillus reuteri showed the fastest and slowest acidification, respectively, and the co-cultures were intermediate. During fermentation, the highest proteolytic activity was found in single culture of Lactococcus lactis subsp. lactis and triple co-culture(peptide content of 1.30 and 1.35 mg/ml) which was followed by a reduction after 7d storage. Peptide content from Lactobacillus reuteri fermentation was not significantly different from that of acidified control milk (ACM). ACM showed no antibacterial activity at the tested concentrations (5-40 mg/ml), while all the fermented milk samples showed antibacterial activities against all five tested pathogens at 40 mg/ml. After fermentation (day 0), the minimum inhibitory concentration of the most of fermented samples was calculated as 20 mg/ml, except for that of triple co-culture-fermented milk which was 40 mg/ml. The antibacterial activity of peptide extracts after 7d storage were varying and starter culture dependent. In overall, in spite that proteolysis resulted in antibacterial activity in the product, no positive correlation was found between proteolytic activity and antibacterial activity.

Probiotics have several advantages for human health. Since most of the probiotic foods are dairy products, they cannot be consumed by humans who are allergic to milk proteins or have severe lactose intolerance. While looking for alternative food matrices, the suitability of carrot juice as a raw material for the production of probiotic food with Lactococcus strain (L. lactis) isolated from local cheese was investigated. Pasteurization of freshly prepared carrot juice at 85°C for 5 min decreased the microbial population and enzymes are disabled (In particular peroxidase). The initial Lactococcus strain concentrations was 109 cfu/5ml of carrot juice, and were kept viable up to the end of fermentation (30 days).Tested Lactococcus lactis strain were capable of growing well on pure carrot juice without nutrient supplementation. Due to intense metabolism of the bacteria strain, carrot juice media were acidified to a pH level of less than 4.During fermentation, the amounts of sugars decreased significantly so that about 50% of which was taken after 24 hours. Degradation of carotenoids was less than 2%. In the case of phenolic compounds the reduction was minimal so that more than 80% of the total phenolic content of Carrot juices was retained in the final product.

Milk، curd، fresh (1-day old) and ripened (90-days old) Lighvan cheese (10 samples from each one) have been investigated for lactic flora as one the most well-known starter free sheep raw milk cheeses. MRS، MRS+vancomycin، M17 and KAA media were used for determining of Lactobacilli and Pediococci، Leuconostocs، Lactoccoci and Enterococci genera، respectively. Isolated strains were identified up to genus level with gram staining and catalase test، morphology، colony pigmentation،gas production from glucose،growth in 10°C and 45°C،salt tolerance،growth at pH9. 6، argenine hydrolysis and citrate utilization. Random colonies were selected from each medium and confirmatory tests showed Enterococcus (33. 68%)، Lactobacillus (33. 68%) and Lactococcus (26. 31%) as the most common genera during the all stages. Finally، these isolated colonies were subjected to carbohydrate fermentation with API 50 CH and API 20 STREP methods and were determined up to species and sub species level. Totally،95 strains were isolated and identified during all production stages. API system results showed the following species: Lactobacillus plantarum، Lb. brevis، Lb. paracasei ssp. paracasei، Lb. delbrueckii ssp. delbreuckii، Lb. fructivorans، Lac. lactis. ssp. lactis، Enterococcus. faecalis، Ent. faecium، Ent. durans، P. pentosaceus، Leu. lactis، Leu. mesenteroides. The lactic acid bacteria changes revealed the pattern that Lactococcus and Lactobacillus were predominant at the first stages and replaced by Enterococcus at the end of production and ripening stage. The most dominant species during all satages follows as: Lac. Lactis ssp. lactis (25. 26%)، Lb. plantarum (20%)، Ent. Faecalis (15. 78%)، Ent. faecium (15. 78%). Thus، we expect that these species may play an important role in ripening and production of Lighvan cheese and also have potential application in industrial scale.

Bovine tuberculosis (TBB) is a zoonotic disease distributed worldwide and is of great importance for public health and the livestock industry. Several experimental vaccines against this disease have been evaluated in recent years, yielding varying results. An example is the Bacillus Calmette-Guérin (BCG) vaccine, which has been used extensively in humans and tested in cattle showing mixed results related to protection (0-80%) against Mycobacterium bovis. In this study, we used the food-grade bacterium Lactococcus lactis as an expression system for production of mycobacterial protein Hsp65. For this purpose, the construction of a replicable plasmid in strain NZ9000 L. lactis (pVElepr) was conducted, which expressed the Mycobacterium leprae Hsp65 antigen, and was recognized by traded anti-Hsp65 antibodies. The strain NZ9000-pVElepr was applied to calves that were negative to tuberculin test and the immune response was monitored. The results showed that immune response was not significantly increased in calves with NZ9000-pVElepr with respect to control groups, and no injury was observed in any lung or lymph of the calves. Finally, this study suggest that the recombinant NZ9000 strain of L. lactis may protect against the development of M. bovis infection, although studies with longer exposure to this pathogen are necessary to conclude the matter.