الفهرس 
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Abstract
The work in this thesis was carried out with the objective to : a) determine the incidence type and species of sporeforming bacteria in UHT milk produced in Egypt b) isolation of psychrotrophic bacteria from cow and buffalo milk.
In the results presented in 3.1 . eighty seven strains of aerobic sporeforming bacteria were isolated from UHT milk manufactured in Egypt by four different dairy plants. Four species of the genus Bacillus were identified, namely B. subtilis, B. megaterium, B. licheniformis and B. pumilus, B. subtilis and B. megaterium were the main two species, they represented 56.32 % and 18.38 % of the total isolates, wheras B. pumilus was the least common species as it represented 9.19 %.
The results of 3.2 showed that maximum protease production by B. subtilis was obtained at the late log phase and early stationary phase when grown in nutrient broth whereas, B. megaterium gave maximum production of protease at the late stage of stationary phase and the early stage of the decline phase of the growth cycle , B. pumilus was found to produce maximum production of the enzyme after three days of the beginning of the stationary phase. Growth and proteolytic activity were quite variable between the isolated Bacillus species