Isolation and Identification of an Alkaline Protease Producing Bacillus from Soil

Document Type : Brief Report


1 Biology Department, Faculty of Science, Shahid Beheshti University, Chamran Highway, Evin, Tehran, Iran.

2 Biology Department, Alzahra University, Vanak Deh, Vanak Square, Tehran, Iran.


Soil samples were screened for alkaline protease producing bacteria on alkaline agar plates containing casein. Alkaline protease production was identified by clear zones of casein hydrolysis around colonies. Such colonies were grown in an alkaline broth for 48-72 h and the enzyme activity of the culture supernatants was  determined by measuring the amount of tyrosine released from casein after 10 min at 35ºC, at a pH of 10.5. A spore forming Gram positive aerobic Bacillus sp. which showed the best enzyme production was chosen  (strain L2). The production medium was optimized for this strain. The best developed medium contained:
1% glucose, 0.5 % peptone, 1% yeast extract, 0.1% KH2PO4 and 0.02 % MgSO4. 7H2O. Alkaline protease activity was highest at pH 11 and 45ºC. Biochemical tests tentatively identified the organism as Bacillus licheniformis.