الملخص

The study was conducted in order to create the best conditions (physical and chemical factors) that necessary for the growth of the Bacillus subtilis and its production of the Xylanase enzyme. The results include isolation and diagnosis of (40) isolates of bacteria: Bacillus subtilis obtained from (30) soil samples and study the effect of some physical factors (period and temperature of incubation, pH of the medium, ventilation) on bacterial growth and its production of an Xylanase enzyme. The results showed that best growth and its production of the enzyme was obtained when the incubation is (48) hours and the temperature (30) Co , pH of the medium (7) and incubation with shaking at (200) rpm where the optical density value of bacterial growth was reached (0.25) and activity of the enzyme product was (3.41) unit / ml. The effect of some chemical agents (carbon and nitrogen source for medium) on bacterial growth and its production of an Xylanase enzyme and the results revealed that the carbon source (Xylan) gave the best growth and production of the enzyme compared with other of carbon sources (Starch, Cellulose, Xylose, Glucose, Sucrose, Maltose, Lactose), where the optical density value of growth was (0.25) and the enzyme activity (3.41) unit / ml. Regarding the effect of the nitrogen source (organic and inorganic) in medium on growth and production of the enzyme, the results showed that the best bacterial growth and the production of an Xylanase enzyme occur when organic nitrogen sources (Peptone, Beef extract, Yeast extract, Casien) were supplemented in the medium compared with inorganic nitrogen sources (KNO3, (NH4) 2SO4, NH4NO3, NaNO3). Peptone and Yeast extract were the best nitrogen sources for stimulation of bacterial growth and the production of the enzyme with optical density value of growth reached (0.29 , 0.286) and the enzyme activity was (3.92 , 3.9) unit / ml.