title: UV mutagenesis for the overproduction of xylanase from Bacillus mojavensis PTCC 1723 and optimization of the production condition.
abstract: OBJECTIVE
  This study highlights xylanase overproduction from Bacillus mojavensis via UV mutagenesis and optimization of the production process.
  
  
  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 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Microbiology, Tehran Science and Research Branch, Islamic Azad University, Tehran, Iran.
authors.forename: Shokoofeh
authors.initials: S
authors.lastname: Ghazi
authors.affiliation: Department of Microbiology, College of Basic Science, Islamic Azad University, Tehran North Branch, Tehran, Iran.
authors.forename: Abbas Akhavan
authors.initials: AA
authors.lastname: Sepahy
authors.affiliation: Department of Biotechnology, Iranian Research Organization for Science and Technology, Tehran, Iran.
authors.forename: Mehrdad
authors.initials: M
authors.lastname: Azin
authors.affiliation: Department of Biotechnology, College of Basic Science, Tarbiyat Modares University, Tehran, Iran.
authors.forename: Khosro
authors.initials: K
authors.lastname: Khaje
authors.affiliation: Department of Microbiology, Tehran Science and Research Branch, Islamic Azad University, Tehran, Iran.
authors.forename: Ramazanali
authors.initials: R
authors.lastname: Khavarinejad
keywords: Bacillus mojavensis; H/C ratio; Optimization; Random mutagenesis; Xylanase