الفهرس 
Introduction and Aim of the WorOnly 14 pages are availabe for public view
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Abstract
The food companies are interested currently to select starter and protective LAB cultures for food fermentation . this is due to the ability of such LAB cultures to produce organic acids, diacetyl , H2O2 , and antimicrobial proteins ( bacteriocins ). The LAB are used also as probiotics to improve human nutritional and physiological function since they decrease pH value to acidity in stomach, degrade lipids and other polymers including polysaccharides and proteins , inhibit pathogenic bacteria in stomach and decrease or prevent lactose intolerant cases in old men ( ≥ 45 years ).
Consequently , this thesis was focused to select and identify some LAB cultures which could be used as starter and protective bacteria for food fermentations and to be exploited as probiotic cultures .
A total of about 33 LAB isolates were isolated from zabady , sausage , pickles , cheese and honey bee samples. These isolate were surveyed for their ability to produce antimicrobial substance(s) against some food_borne pathogens including E . coli , St . pyogenes , S. aureus, B . cereus and L . monocytogenes . Almost 40 % of LAB cultures showed inhibitory activity . Two isolates namely : PO24 & CK28 isolated from pickles , kareesh cheese samples respectively showed the higher antibacterial activity against E . coli , St . pyogenes , S . aureus and L . monocytogenes . In addition , the CK28 isolate inhibited B. cereus .
The PO24 and CK28 isolates decreased pH of the medium from pH 7.0 to pH 3.6 – 4.0 with in 24 h ; this is interested property for any LAB isolate since it can consume media sugars and ferment it , giving lactic acid . This enable the LAB cultures to be used as ideal starter culture for food fermentations .