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Background: Fresh milk and natural environmental conditions are used to produce traditional cheeses. Such cheeses are produced by dozens of different types of microbes. Non-starter lactobacilli are the most responsible genus of lactic acid bacteria exhibiting key technological and health promoting traits. The purpose of this study is to isolate Lactobacillus bacteria from conventional Egyptian cheeses and analyse their probiotic potential and technological properties. Results: Lactobacillus isolates (33 isolates) were isolated from different Egyptian cheeses. Our results revealed that 18.18% of the isolates were fast-acidifying, 30.3% were medium-acidifying and 51.5% were slow-acidifying isolates. The results of autolytic activity showed that 24.3% of the isolates were good autolysis, 33.3% were fair autolysis, while 42.4% were poor autolysis. Fifteen isolates produced exopolysaccharides, while 9 isolates exhibited antimicrobial activities against Lactobacillus bulgaricus 340. All the isolates were resistant to pH 3 for 3 h except isolate No. 15 (MR4). The growth rate of the isolates ranged from 42.25 to 85.25% at 0.3% bile salts after 3 h of incubation. The surviving percentage of the Lactobacillus isolates decreased with increasing incubation time or the percentage of bile salts greater than 0.3%. All the isolates grew after incubation in artificial gastric and intestinal fluids. The auto-aggregation of 15 isolates ranged from 43.13 to 72.77%. Lacticaseibacillus paracasei BD3, Lactiplantibacillus plantarum BR4 and Limosilactobacillus fermentum MR2 were sensitive to the majority of the tested antibiotics and showed good bile salt hydrolase activity. Conclusion: L. paracasei BD3, L. plantarum BR4 and L. fermentum MR2 were isolated from Egyptian cheeses and showed probiotic and technological characterization, which are valuable for their practical application as starters, adjunct and protective cultures in cheese making. [ABSTRACT FROM AUTHOR]

Lactococcus lactis subsp. lactis A15 and Enterococcus faecium A15 had antimicrobial activity against Listeria monocytogenes EGDEe 107776. Bacteriocins produced from isolated strains are stable between pH 5 and 8 and stable also until 100C for 10 min. The amount of bacteriocin produced by Lactococcus lactis subsp. lactis A15 reached to the maximum (2560 AU/mL) at the end of logarithmic phase while Enterococcus faecium A15 was observed in logarithmic phase. PCR results revealed the presence of nisin Z structural gene in Lactococcus lactis subsp. lactis A15 and enterocin B gene for Enterococcus faecium A15. Lactococcus lactis subsp. lactis A15 was free from genes of asa1, gelE, espfm, cylA, efaAfs. Otherwise, Enterococcus faecium A15 did not contain an asal, espfm and cylA genes. Tested strains were sensitive to kanamycin, vancomycin and gentamycin. Tested strains were not able to hydrolyze red blood cells. Practical Applications Nowadays, the addition of bacteriocins and/or bacteriocin-producing lactic acid bacteria (LAB) as natural food preservatives to food products (i.e. cheese and yoghurt) has been considered with the aim of increasing the food safety of these products. Bacteriocins have successfully been used to control Listeria monocytogenes. Lactococcus lactis subsp. lactis A15 could be used as starter culture or co-culture in food system for preventing the growth of Listeria monocytogenes and increasing the safety and shelf-life of dairy products. Enterococcus faecium A15 was able to produce gelatinase but not able to hydrolyze red blood cells. On the other hand, the bacteriocin produced from Enterococcus faecium A15 may find application as bio-preservatives for increasing the shelf-life of Egyptian Dairy products. [ABSTRACT FROM AUTHOR]

ABSTRACT Proteolytic activity of Lactobacillus helveticus A75 and effects of caseins hydrolysis by this strain on their immuno-reactivity were studied. Proteases of L. helveticus A75 hydrolyzed both αS1- and β-caseins and were inhibited by serine- and metallo-proteases inhibitors. Polymerase chain reaction amplification revealed the presence of prtH gene, which was 99% identical to prtH gene of L. helveticus CNRZ 32. Effect of proteolysis of αS1- and β-caseins by L. helveticus A75 on their immunoglobulin E (IgE) binding ability was studied by an enzyme-linked immunosorbent assay with the pool of eight sera from cow milk allergy patients. The IgE binding ability of hydrolyzed proteins was lower than that of intact proteins, which indicates that hydrolysis of αS1- and β-caseins by proteases of L. helveticus A75 decreases their recognition by specific IgE. Half maximal inhibitory concentration values were 2.01 and 2.28 µg/mL for αS1- and β-casein, respectively, and increased until 9.08 and 13.65 µg/mL, respectively, after their hydrolysis by L. helveticus A75. PRACTICAL APPLICATIONS The obtained results yield new information about proteolytic activity and potential application of lactobacilli isolated from traditional Azerbaijani cheeses. Isolated strain could represent new adjunct cultures for the dairy industry. [ABSTRACT FROM AUTHOR]

Proteinase activity of Lactobacillus fermentum IFO3956 cells was higher when they were grown on milk-based media than on 10% reconstituted skim milk. The lowest protease activity was observed when cells were grown on milk-free media. The extraction of milk-induced cell-bound proteases from Lb. fermentum IFO3956 was most efficient using 1% Tween 80 while the use of 1% SDS inhibited all proteolytic activity. Two bands of ∼35 and >100 kDa were observed by zymogram, indicating that proteolytic activity corresponded to the presence of at least two types of enzymes or two molecular forms of one enzyme. Mass spectrometry analyses of αS1-casein hydrolysates detected 24 peptides with sizes ranging from 5 to 36 amino acids, including 9 phosphorylated peptides, resulting from the fermentation of Lb. fermentum IFO3956 of αS1-casein. Most of the identified peptides originated from the N-terminal portion of αS1-casein. The studied bacterial strain could hydrolyze αS1-casein in many sites including the epitopes triggering the allergic reactions against αS1-casein e.g. at the positions 23, 30, 41, 71, 91, 98, 126, 179. After hydrolysis of αS1-casein with Lb. fermentum IFO3956 the recognition and the binding of this casein to IgE from the pooled sera of 18 patients with cow's milk allergy was significantly reduced. [ABSTRACT FROM AUTHOR]