Induction of overproducing alkaline protease Bacillus mutants

Bacillus pumilus and Bacillus alvei, among alkaline protease producing strains, were used to examine the changes in alkaline protease gene expression following UV irradiation. Induction of mutation in Bacillus mutant strains was carried out by 0, 5, 10, 15 and 20 min. exposure times of UV irradiation and different distances between the treated bacterial cultures and UV source. Results revealed that alkaline protease activity assayed under submerged culture conditions was more accurate than the relative growth production (C/G) method, because there was no proportional correlation between zone diameter and the ability to produce the enzyme in submerged cultures. No enzyme activity was scored with B. pumilus mutants, while the activity was pronounce, in case of B. alvei mutants. Mutants No.15, 55 and 34 were the most efficient in enzyme production under submerged conditions being 68.8, 81.1 and 99 U/ml, respectively. Their alkaline protease activities were 2.6, 3.02 and 3.7 folds than those of the original strains. The optimal enzyme production was achieved after 48 hr at air: medium ratio of 39: 1. Results also proved that the inoculum size in all tested mutant ranges had no significant effect on the enzyme production.The supplementation with glucose to growth medium gave the highest level of enzyme productivity, while lactose showed the lowest. The addition of arabinose and xylose completely inhibited the enzyme production by both tested strains, while incorporation into the culture medium of sucrose and maltose failed to produce the enzyme in B. alvei, but in mutant No.8, they enhanced high levels of productivity