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Production of alkaline
protease and larvicidal biopesticides by an Egyptian
Bacillus sphaericus isolate
Abd El-Moneim M. R. Afify1, Mourad A. M.
Aboul-Soud2, Mohammed S. Foda3,
Mahmoud W. A. Sadik4, Tarek Kahil3;
Amira R. Asar3 and Abdulaziz A. Al-Khedhairy2
1Biochemistry
Department, Faculty of Agriculture, Cairo University, 12613
Giza, Egypt.
2DNA
Research Chair, College of Science, King Saud University,
P.O. BOX 2455, Riyadh 11451, Kingdom of Saudi Arabia.
3Microbial
Chemistry Department, National Research Center, Giza, Egypt.
4Microbiology
Department, Faculty of Agriculture, Cairo University, 12613,
Giza, Egypt.
*Corresponding author.
E-mail:
maboulsoud@ksu.edu.sa.
Accepted 27 August, 2009 |
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One strain, isolated from Egyptian soil, was identified as
Bacillus sphaericus with powerful larvicidal toxicity
against C. pipiens and extra-cellular production of
alkaline protease (AP) in the growth medium. The pH
adjustment of the growth medium between 6.0 and 7.5 resulted
in the highest AP activity, peaking at pH 6.5. AP crude
preparations exhibited optimum activity at pH 10 and at
temperature range of 65 - 70ºC. Interestingly, the highest
AP activity was observed with 3% fodder yeast, as the sole
component of the medium. Moreover, optimal AP yield was
attained by using strong aeration at 9:1 (air : medium)
ratio. Similarly, the highest AP enzyme level was
consistently achieved 3-day after aerobic growth in shake
flasks at 30ºC, without significant decrease in AP yield
upon extended incubation periods up to 6 days. Notably,
maximum proteolytic activity was achieved with casein as a
substrate followed by skim milk, gelatin and bovine serum
albumin. The crude AP enzyme activity exhibited quasi-linear
response with enzyme concentrations up to 0.25 mg ml-1.
The isolated B. sphaericus might be employed for the
economic production of important products such as
biopesticides and proteolytic enzymes.
Key
words:
Biopesticides, Larvicidal activity, Alkaline protease,
Bacillus sphaericus, Fodder yeast. |
