The protease produced by a Bacillus pumilus CN8 strain was purified by DEAE-Cellulose-52 ion exchange. It has a molecular weight of approximately 96,920 Dalton. In the present study, this protease showed strong activity over a broad range of pH (6.5-9.5) and temperature from 40℃ to 60℃, and the protease performed the maximal activity at pH 7.3 at 42℃. The effect of metal ions on protease activity showed that K+ could slightly increase the protease activity, and other ions such as Zn²+, Fe²+, Na+, Ca²+, Mg²+ had no significant activation or inhibition to the protease (P > 0.05), and the more important is that Cu²+, Mn²+, Sn²+, Cd²+ had a strong inhibitory effect on the protease activity.

Background : The purpose of the present investigation is to enhance extracellular acidic protease production by subjecting a protease producing strain Cordyceps pruinosa DK-01 to random mutagenesis by UV irradiation after ethidium bromide treatment. Methods and Results : Mutants were screened as protease producers on the basis of zone of clearance and relative proteolytic activity (RPA) on skimmed milk agar plates. In addition, mutants showed strong pink-red color intensity and different RAPD profiling compared with wild type control. Four mutants were randomly selected and their extracellular enzyme activities were investigated. In liquid culture without casein, 2.2-, 2.9-, 5.2- and 4.4-fold higher acid protease activity was achieved from mutants DK-m9, -m11 and -m12, respectively, than that of wild type strain (11.13 ± 1.60 U/ml). In liquid culture with casein, 1.1-, 1.3-, 1.3 and 1.3-fold higher acid protease activity was achieved with those mutants were found to produce, respectively, than that of wild type strain (93.95 ± 12.84 U/ml). Maximum acid protease activity was noticed from a mutant DK-m11 in liquid culture with casein (121.18 U/ml) and without casein (57.65 U/ml). The extracellular acid protease produced from DJ-m11 that was active in the pH range 4.5-6.5 and optimum temperature for the activity was 37°C. Furthermore, we found a deformed, shorten structure of setae on the elytron surface of dynastid beetles treated with culture supernatant of the DK-m11. Conclusion : These findings have more impact on enzyme economy for biotechnological and insecticidal applications of fungal proteases.

우리나라 전통발효식품의 하나인 청국장으로부터 고 비활성 세포외 protease 생산능이 우수한 균주를 분리하고 그 특성을 조사하였다. 분리된 균주 중 D14 균주 배양 상징액의 protease 활성이 15.2 U/mL로서 가장 강하였으며 비활성 또한 40.0 U/mg protein으로서 가장 강하게 나타났다. 이 균주의 특성을 조사한 후 Berge's Manual of Systematic Bacteriology에 준하여 Bacillus subti