The antibacterial effect of mixed culture of Lactococcus lactis subsp. lactis and Lactobacillus delbrueckii subsp. bulgaricus against some food borne pathogenic organisms were investigated. Much amount of acidity was produced by lactic acid bacteria and increased gradually with the fermentation time. Lating of reaching pathogens to milk lead to the over increasing of acidity produced by lactic acid bacteria. Over production of acidity aod reduction of pH level and other substances not determined lead to prevent or inhibit the growth of all pathogens. These factors clearly showed the inhibition effect of lactic acid bacteria against pathogens. The count of all pathogenic, organisms decreased sharply with fermentation time until it disappeared completely after 3 days. This shows the importance of the consumption of fermented milks. Cell-free extract of lactic acid bacteria shows clearly an inhibitory activity against all pathogenic organisms used. But, non-boiled extract was highly active than those of boiled ones. This means that, lactic acid bacteria produced thermolabile substances inhibit or prevent the growth of pathogens. Finally all these observations show the hygienic and nutritional importance of the consumption of fermented milks.

Xanthan gum is a biopolymer heteropolysaccharide used in wide variety of foods / feed and other applications such as pharmaceuticals, cosmetic, petroleum production and other industries. Therefore, this study was aimed to produce highest amount of xanthan by Xanthomonas campestris grown on some industrial wastes and the results are summarized as follow: xanthan gum was maximized on the fourth day of fermentation with Garcia -Ochoa's medium supplemented with 3% sucrose + 5% corn steep liquor, which they stimulated the production of xanthan by tested organism. The addition of molasses such as sugar cane or beet as well as sugar cane juice and whey to the fermentation medium reduced greatly the production of xanthan, but the addition of whey plus whey hydrolyzed enzyme and sucrose to Garcia -Ochoa's medium enhanced the production of xanthan. Potato starchy waste reduced the production of xanthan with much more amount, but xanthan production was enhanced greatly with the addition of glucose syrup to the production media. Also, glucose syrup at 0.6% plus potato starchy waste (3%) gave over production of xanthan by Xanthomonas campestris. This means that, some available low price industrial wastes and raw materials may be used for highest production of an important product from microbes such as xanthan gum.

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The inhibition of some undesirable microorganisms namely Escherichia coli, Staphylococcus aureus, Salmonella typhimurium, Listeria monocytogenes and Bacillus cereus in fermented milk (Zabady) by mixed cultures of yoghurt (Streptococcus salivarius subsp. thermophilus and Lactobacillus delbreuckii subsp. bulgaricus) was studied. Results of this study revealed that acidity of Zabady treatments increased, while pH values decreased throughout storage period. The rates of increasing acidity and decreasing pH values were higher in treatments stored at room temperature than those stored at 5-7C. Counts of target organisms declined sharply in the presence of lactic starter. The rate of disappearance at room temperature was higher than that at 5-7C. The inhibition zone varied with the different target organisms. Supernatant obtained from the harvest of lactic culture incubated at room temperature had higher inhibitory effect than that at 5-7C. Non boiled fluid had greatest effect than boiled extracts.