الفهرس 
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Abstract
Bacteriocins are natural antimicrobial peptides which can be used as food preservatives or in pharmaceutical fields, but it is faced with restrictions such as low yield and limited antibacterial activity. Nanotechnology has lately been used as a promising solutions to combat these problems.
Our aim was to synthesize bacteriocin incorporated nanoparticles to overcome some of the hurdles that natural bacteriocin faces. To accomplish this, the present study was planned to investigate the bacteriocin–producing Lactic acid bacteria (LAB) strains from raw milk and traditional dairy products of Luxor province-Egypt. The second step was to define these strains at the species level and to determine their bacteriocins-encoding genes using molecular techniques (PCR). Finally synthesis bacteriocin-incorporated nanoparticles and comparing its antibacterial activity with the natural one.
The results of this study indicated that 30 LAB isolates were found to be antimicrobial producers. These isolates exhibited a potential antibacterial activity against all tested indicators, except for Listeria monocytogenes. Additionally, it was revealed that 22 of isolates were identified as Lactobacillus plantarum, while 8 were Leuconostoc mesenteroides. Beside plnEF gene was recognized at 9 Lb. plantarum genome, some of which also had plnA gene. Whereas, the MesY gene has been detected in Lc. mesenteroides strain-No.16. Strains No.7 (LPL.7) and No.13 (LPL.13) were chosen for further investigation based on their antibacterial activities. PlnEF EG.LP.7 and PlnEF EG.LP.13 genes encoding plantaricin EF, were sequenced and deposited under accession No. MN172265 and MN172264 respectively.
Abstract
In addition, LPL.7 plantaricin A encoding gene ”plnA Egypt 2018” sequence was deposited under accession No. ”MN172266”.
Bacteriocins extracted from both selected strains were used for synthesizing different bacteriocin (plantaricin)-incorporated nanoparticles. Bacteriocin-incorporated silver nanoparticles (B-SNPs) have exhibited a remarkable inhibitory effect against Staph. aureus. Through comparing the antibacterial activity, the total antibacterial activity of natural bacteriocin for strain LPL.7 and LPL.13, were 80 and 160 AU/ml, whereas it became 10240 and 20240 Au/ml for B-SNPs, respectively. One of the significant finding that B-SNPs displayed inhibitory activity against Listeria monocytogenes. Another significant observation has been to increase the stability of natural bacteriocins obtained from LPL.7 and LPL.13, which was five days and reached to 60 days at 4ºC for the B-SNPs, respectively. In conclusion, this study is the first in Luxor province, upper Egypt to describe plantaricin- incorporated silver nanoparticles. Which is more effective at lower concentrations, has a wider range of susceptibility and also a more stability than natural one.