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The effects of Pediiococcus acidilactici and Lactococcus lactis was evaluated on survival rate and some immunological parameters of L. vannamei during three months of cultivations. Treatments included control group, Pediococcus and Lactococcus treatments and probotic treatmentsfed at 1×10⁹ cfu g^-1. The results indicated that probiotics increased the survival rate (P<0.05). The best immune performance was shown in the probiotics treatments; phenoloxidase activity, proteins, and globulin hemolymph showed  significant difference compared to the control treatment (P<0.05), whereas there were no significant influence on lysozyme activity (P≥0.05). In general, pediococcus treatment showed the best performance in enhancing the immune responses and survival rate.  

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  In this research diacetyl production as a buttery flavor in food industries by Lactic Acid Bacteria (LAB), Lactococcus and Leuconostoc genus was investigated. Batch fermentation process accomplished on MRS (De Man, Rogosa and Sharpe medium) broth medium, medium based on whey powder and based on skim milk powder at different conditions of temperature, agitation speed, glucose as carbon source, tri-sodium citrate as precursor of diacetyl production, inoculum, catalase enzyme, bovin blood as heme protein source and CuCl2. Optimum conditions were determined for achivement of highest production yield.  This research indicated that the optimum fermentation conditions for diacetyl production by LAB were:32º C, 180 rpm, glucose 6 g/l,tri-sodium citrate 5g/l, inoculun 5%, catalase enzyme 6 ml/l, bovin blood 4 g/l, CuCl2 15 mg/l. Finally, for production of diacetyl, a fermenter was used with 10 liter volume, inoculum size 5 % (v/v) with working volume of 6.5 liters. Agitation and temprature were maintained at 180 rpm and 32ºC, respectively. Diacetyl concentration under optimized condition in fermenter was obtained as 945 mg/l.

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Molds can be noted as one of the major factors in bread corruption that mainly caused by Aspergillus, Fusarium and Penicillium. In addition to the economic losses caused by mold, types of toxins produced by them can also cause health problems. Chemical preservative such as propionic and sorbic acids are mainly used for preventing mold growth that it is not receptive to consumers. In recent years due to increasing public awareness, Customers demand to reduce the use of chemicals and the use of natural preservatives. Lactic acid bacteria are one of the biological preservatives that because of the antimicrobial properties and in some cases due to the positive effects on organoleptic properties have received much attention. In this project, the effect of spraying the bacterium Lactococcus lactis PTCC 1336 at three concentrations (zero, 10⁴ cfu /cm² and 10⁶ cfu /cm²) and also the combined use of calcium propionate in three levels , zero, 2 and 4 % (w/w) on improving the duration of preservation and its effect on organoleptic properties of bread and also its effect on reducing the amount of calcium propionate was investigated. In those bread, the quantity of pH, acidity, and the amount of mold formation (macroscopic and laboratory observations) were measured. The results showed Spraying bacterium Lactococcus lactis PTCC 1336 on bread Can be more powerful Compared with calcium propionate Compared with calcium propionate reduces the mold. So the least amount of mold at the sample M3P3 (Samples containing 10⁶cfu/cm², 0.4% PC) observed.  as well The results showed concomitant use of Lactococcus lactis PTCC 1336 and calcium propionate Activity on mold synergistic effects are produced.

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The use of genetically engineered probiotics to express specific enzymes has been the subject of considerable attention in poultry industry because of increased nutrient availability and reduced cost of enzyme supplementation. Phytase enzyme is commonly added to poultry feed to improve digestibility and availability of phosphorus from plant sources. To construct a probiotic with potential of phytate degradation, phytase gene (appA) from E. coli was cloned and transformed into two probiotic bacteria Lactobacillus salivarius and Lactococcus lactis. The results showed plasmid instability, unable to express the gene. The expression of appA gene in L. lactis was analyzed by detecting specific RNA and zymography assay. Phytase enzyme was isolated from cellular extracts of recombinant L. lactis, showing a 46 kDa band upon the SDS-PAGE analysis. Zymogram also confirmed the phytase activity of the 46 kDa band corresponding to the enzyme. An enzyme activity of 4.9 U mL^-1 was obtained in cell extracts of L. lactis. The growth of native and recombinant L. lactis was similar in the presence of two concentrations of ox bile.

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In the present research work, the potential probiotic properties of Lactococcus lactis KMCM3 and Lactobacillus helveticus KMCH1 isolated from raw camel milk and traditional fermented camel milk (Chal), respectively, were studied. The probiotic properties of isolates that were investigated included the hemolysis, antibiotic resistance, antibacterial features, resistance to low pH and bile salts, survival under simulated GastroIntestinal Tract (GIT) conditions, adhesion ability to hydrocarbon, and their auto-aggregation and co-aggregation rates. None of isolates exhibited hemolytic activity. They were susceptible against tetracycline, penicillin, ampicillin, chloramphenicol, erythromycin and vancomycin. Lac. lactis KMCM3 and L. helveticus KMCH1 retained their viability at pH 3.0 (8.68 and 8.6 log cfu mL^-1, respectively), 0.3% w/v bile salts (8.23 and 8.58 log cfu mL^-1, respectively) and under simulated GIT conditions (8.31 and 8.46 log cfu mL^-1, respectively). Both of these isolates inhibited the growth of E. coli, S. aureus, L. monocytogenes, B. cereus and S. enterica subsp. enterica serovar Typhimurium with MIC values of 6.25 to 25 mg mL^-1. In addition, They exhibited an ability to adhere to hydrocarbon (xylene), and possessed a high auto-aggregation and co-aggregation rate (more than 40%).
 

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Bread enrichment with fiber-rich leafy vegetables and fermented by-products of milling has gained more attention in recent years. In the present study, the antifungal lactic acid bacterium isolated from Tarkhineh was used as starter culture in controlled wheat germ sourdough in order to improve quality and safety of the white wheat bread containing wheat germ sourdough along with dehydrated spinach puree. The optimized formulation (10% wheat germ sourdough and 20% dehydrated spinach puree, which were replaced by wheat flour) was determined based on the crumb softness of the enriched breads. Then, the quality characteristics of the supplemented breads were studied in terms of textural properties, antioxidant activity, surface moldiness, phytic acid content and organoleptic acceptability. The sequencing of polymerase chain reaction products led to the identification of Lactococcus lactis as the selected antifungal lactic acid bacterium isolate. Texture profile analysis revealed the significant effect (P< 0.05) of wheat germ sourdough and dehydrated spinach puree on crumb hardness and loaf specific volume of the produced breads. Bread containing wheat germ sourdough along with dehydrated spinach puree had the highest radical scavenging activity. Green zone of Asprgillus flavus growth on wheat germ sourdough supplemented bread and phytic acid content of the aforementioned sample were also remarkably lower than the others. Furthermore, there was no significant difference between bread enriched with wheat germ sourdough and wheat germ sourdough along with dehydrated spinach puree in terms of sensory acceptability compared to the control sample.