Increasing the alkaline protease activity of <i>Bacillus cereus</i> and <i>Bacillus polymyxa</i> simultaneously with the start of sporulation phase as a defense mechanism

Abstract

In this research, the growth curve, curve of sporulation phase and alkaline protease activity of Bacillus cereus and Bacillus polymyxa were compared and examined simultaneously. These examinations showed that, the production of alkaline protease started with the beginning of the log phase in the growth curve simultaneously and after a small stop according to the stationary phase increased and then with the start of the death phase, increased rapidly again. The maximum alkaline protease activities of B. polymyxa and B. cereus were measured at the death phase of the growth curve and at the start of the sporulation phase of the two microorganisms. The mentioned experiments were made in glucose synthetic medium at 30°C with 100 rpm aeration speed for 144 h. The maximum alkaline protease activity of B. cereus and B. polymyxa occurred after 72 h simultaneously with the start of the sporulation phase of the two bacteria and were measured at 383 and 418 u/ml, respectively. The next experiments showed that, the enzyme was very stable in extreme conditions such as freezing, drying and lyophilization. Also, it protected 98 to 100% of its primary activity after 4 months in the mentioned conditions.

Key words: Sporulation phase, alkaline protease, Bacillus cereus, Bacillus polymyxa, extreme conditions.