Effect of physical and chemical mutagenesis on the ability of locally isolated bacillus stearothermophilus in protease production

الملخص EN

Ninety three soil samples were collected from different locations in Basra governorate.

From these samples, 53 bacterial isolates of a thermophilic Bacillus spp.

were obtained, all these isolates were identified according to their morphological and cultural characteristics and biochemical tests.

Results showed that 6 of these isolates are identified as Bacillus stearothermophilus.

These isolates were screened according to their ability of protease production, and it was found that all these isolates were protease producers, among them B.

stearothermophilus B17 was the most efficient in protease production.

Specific activity of protease in crude filtrate of this isolate was 36.4 U/mg protein.

Ability of B17 in protease production developed by mutagenesis using physical and chemical mutagens.

Results showed that physical mutagenesis using UV irradiation caused to obtain two over producer mutants out of 45 (13.3%) increased in their ability in protease production.

Specific activity of protease in crude filtrate of these two mutants are 54.4 and 80.08 U/mg protein respectively in comparison with 36.4 U/mg protein for the wild-type, while chemical mutagenesis by using MNNG was also lead to obtain one over producer mutant out of thirty two (3.1%) increased in its ability in protease production.

Specific activity of protease in culture filtrate of this mutant was 99 U/mg protein in comparison with 36.4 U/mg protein for the wild-type.