الفهرس 
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Abstract
Alternative substrates to produce useful bioactive agents such as enzymes have been attractive and important. Rice straw and corn cobs considered as the most abundant lignocelluloses wastes by-products in Egypt which can be used for this purpose. The present study was aimed to produce xylanase by B. subtilis and S. cervisiae which cultivated on treated alkalinity rice straw and corn cobs using solid state fermentation technique. Results indicated that, the highest yield of xylanase enzyme was obtained from B. subtilis and S. cervisiae cultivated on substrate consists of mixture from rice straw and corn cobs 0:5 and 1:4 of rice straw : corn cobs that incubated for 3 days at 37°C ± 2°C, which lead to produce 13.51 mmol enzyme. The properties of the produced xylanase were studied. However, the optimum pH values of xylanse derived from B. subtilis were 4 to 5 and 6-7 for xylanase of S. cervisiae and the best stability for the enzyme of incubated for 30,60 and 120 min for the two strains was at pH 6 and 37°C. Meanwhile, the activity of xylanase derived from both S. cervisiae and/or B. subtilis increased gradually by raising the temperature between 50 and 60°C then declined by rising the temperature over 60°C.Results also showed that, the best stability of xylanase was at 60°C for incubated enzyme at 30, 60 and 120 min. On the other hand, the gradually increasing of the velocity for the reaction of xylanase obtained from the two tested strains up to 1ml of enzyme concentration. Moreover, the present study was carried out to prepare fiber gel from some the tested cereal wastes (Rice straw and Corn cobs) and used them as flour replacer in the production of high dietary fiber and low caloric cookies and beef burger.