Production of alkaline protease by Bacillus cereus and Bacillus polymixa in new industrial culture mediums and its immobilization

Abstract

After amylases, proteases are the most useful industrial enzymes that are produced 500 tones annually. In industry, proteases are produced from bacteria and fungi. The alkaline proteases, with an optimum activity in pH: 9 - 11, have numerous applications in daily life of peoples such as food complementary of beast and poultry, confectionary, bakery, fermentation industries, leathering, detergent industry, biotransformation and so on. In this research a wild strain of Bacillus cereus andBacillus polymixa, isolated from the soils of Isfahan (Iran), showed the best alkaline protease activity in industrial mediums such as sweet sorghum extract and molasses. The maximum alkaline protease activity in productive culture mediums after 72 h in 30°C and with100 R.P.M. were measured. The results with B. polymixawere 46.7 (u/ml) in T.S.B, 57 (u/ml) in N.B, 60.22 (u/ml) in peptone solution, 67 (u/ml) in sweet sorghum solution, 216 (u/ml) in yeast extract solution, 358 (u/ml) in glucose solution, 413 (u/ml) in casamino acid solution, 418 (u/ml) in whey, 470.5 (u/ml) in casein solution, 490.5 (u/ml) in molasses, 525 (u/ml) in sweet sorghum extract and 580.5 (u/ml) in milk and with B. cereus were 34.72 (u/ml) in T.S.B, 39.85 (u/ml) in N.B, 39.1 (u/ml) in peptone solution, 58 (u/ml) in sweet sorghum solution, 200.65 (u/ml) in yeast extract solution, 363 (u/ml) in glucose solution, 191.5 (u/ml) in casamino acid solution, 302.5 (u/ml) in whey, 455.5 (u/ml) in casein solution, 485.5 (u/ml) in molasses, 510.5 (u/ml) in sweet sorghum extract and 535.5 (u/ml) in milk. The fixation experiments with alkaline protease from B. polymixa showed that this enzyme after 3 month in sawdust, perlit and silica has protected its stability and has 50, 100 and 100% of its primary activity respectively. In the case of immobilization with the same enzyme and the same bacterium, the examinations showed that the alkaline protease activity on perlit after one, two and three washing treatment were 52, 30 and 20% of its primary activity but in the case of silica were 93, 90 and 84% of its primary activity. Key words: Alkaline-protease, Bacillus polymixa, Bacillus cereus, sweet-sorghum, immobilization.