UV mutagenesis for the overproduction of xylanase from Bacillus mojavensis PTCC 1723 and optimization of the production condition

Objective(s):[p1]  This study highlights xylanase overproduction from Bacillus mojavensis via UV mutagenesis and optimization of the production process. Materials and Methods:Bacillus mojavenis PTCC 1723 underwent UV radiation. Mutants’ primary screening was based on the enhanced Hollow Zone Diameter/ Colony Diameter Ration (H/C ratios) of the colonies in comparison with the wild strain on Xylan agar medium. Secondly, enzyme production of mutants was compared with parental strain. Optimization process using lignocellulolytic [AGA2] wastes was designed with Minitab software for the best overproducer mutant. Results: H/C ratio of 3.1 was measured in mutant number 17 in comparison with the H/C ratio of the parental strain equal to 1.6. Selected mutant produced 330.56 IU/ml xylanase. It was 3.45 times more enzyme than the wild strain with 95.73 IU/ml xylanase. Optimization resulted 575 IU/ml xylanase, with wheat bran as the best carbon source, corn steep liquor as the best nitrogen source accompanied with natural bakery yeast powder, in a medium with pH 7, after 48 hr incubation at 37°C, and the shaking rate of 230 rpm. Optimum xylanase activity was assayed at pH 7 and 40°C. Enzyme stability pattern shows it retains 62% of its initial activity at pH 9 after 3 hr. It also maintains up to 66% and 59% of its initial activity after 1 hr of pre-incubation at 70°C and 80°C. Conclusion: Mutation and optimization caused 5.9 times more enzyme yield by mutant strain. Also this enzyme can be categorized as an alkali-tolerant and thermo-stable xylanase.