UV mutagenesis for the overproduction of xylanase from Bacillus mojavensis PTCC ۱۷۲۳ and optimization of the production condition

Objective(s):[p۱]  This study highlights xylanase overproduction from Bacillus mojavensis via UV mutagenesis and optimization of the production process. Materials and Methods:Bacillus mojavenis PTCC ۱۷۲۳ 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 [AGA۲] wastes was designed with Minitab software for the best overproducer mutant. Results: H/C ratio of ۳.۱ was measured in mutant number ۱۷ in comparison with the H/C ratio of the parental strain equal to ۱.۶. Selected mutant produced ۳۳۰.۵۶ IU/ml xylanase. It was ۳.۴۵ times more enzyme than the wild strain with ۹۵.۷۳ IU/ml xylanase. Optimization resulted ۵۷۵ 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 ۷, after ۴۸ hr incubation at ۳۷°C, and the shaking rate of ۲۳۰ rpm. Optimum xylanase activity was assayed at pH ۷ and ۴۰°C. Enzyme stability pattern shows it retains ۶۲% of its initial activity at pH ۹ after ۳ hr. It also maintains up to ۶۶% and ۵۹% of its initial activity after ۱ hr of pre-incubation at ۷۰°C and ۸۰°C. Conclusion: Mutation and optimization caused ۵.۹ times more enzyme yield by mutant strain. Also this enzyme can be categorized as an alkali-tolerant and thermo-stable xylanase.

Keywords:

Bacillus mojavensis , H/C ratio , optimization , Random mutagenesis , Xylanase