Effect of environmental and nutritional conditions on protease production by a Bacillus sp. isolated from soil sample of Lavizan jungle park

Soil samples of Tehran parks were screened for proteolytic Bacilli. 40 isolates were obtained from 5 soil samples، of which 18 isolates had the potential of producing proteases based on screening on skim milk agar. By comparing the diameter of clear zones، one of the isolates obtained from Lavizan park، in north east of Tehran، was selected for further experimental studies. This isolate was identified as Bacillus sp. CR-179 based on cellular morphology، gram staining، biochemical test، and finally partial sequence of 16S rDNA. Various nutritional and environmental parameters affected protease production by Bacillus sp. Protease production by this Bacillus cultivated in liquid cultures containing 1% starch as a carbon source and 0. 4% corn steep liquor as a nitrogen source reached a maximum at 24 h، with levels of 340. 908U/mL. Starch and maltose were the best substrates for enzyme production while some pure sugars such as fructose، glucose and sucrose could not influence production of protease. Among various organic nitrogen sources corn steep liquor، which is commercial، was found to be the best substrate followed by yeast extract، whey protein and beef extract. Bacillus sp. CR-179 Could not utilize urea as an inorganic nitrogen source to grow and produce protease. The optimal pH and optimal temperature of enzyme production were 8. 0 and 45°C، respectively. Studies on enzymatic characterization revealed that crude protease showed maximum activity at pH 9. 0 and 60°C، indicating the enzyme to be thermo-alkaline protease.