The cultures namely Brevundimonas olei No.(15),Bacillus subtilis No.(28) and Bacillus cereus No.(32)  which were found to be the most producing of L-aspaginase producing isolates from soil at Fayoum Governorate, has been used in this investigation. Results showed that, the highest enzyme activity was obtained at pH 8.0 for Brevundimonas olei No.15 at incubation temperature 30 ⁰C. Low level of L- asparaginase production by Bacillus subtilis No.28 occur at pH 7.0 at incubation temperature 30⁰C, reached its maximum level at pH 9.0 at incubation temperature 40⁰C. Also, the effects of different carbon sources on enzyme production were studied i.e. dextrose, sucrose, Fructose, Lactose and Mannitol at the concentration of (0.5%) at various incubation period 24, 48 and 72 hrs. Results that, indicated that, Brevundimonas olei No.15 gave the highest enzyme yield being (444.8 IU/ml.) after 24 hrs. fermentation period using mannitol as a sole carbon source followed by dextrose (391.0 IU/ml.), lactose  (390.0 IU/ml.) , sucrose (386.2 IU/ml.) and fructose (379.3 IU/ml.) respectively. Orange and potato peels were examined as a carbon source for production of L-asparaginase. Therefore, orange or potato peels were added to the modified M9 broth medium and substituted glucose. Generally results showed that, potato peels gave the highest L-asparaginase yield than orange peels for all investigated bacterial strains.