title: Improvement in bioreactor productivities using free radicals: HOCl-induced overproduction of xanthan gum from Xanthomonas campestris and its mechanism.
abstract: Free-radical induction has been employed as a novel strategy to improve bioreactor productivity and, more specifically, the quality and productivity of xanthan gum from Xanthomonas campestris cultures. A 210% increase in xanthan yield and a 20% increase in viscosity (quality) resulted from HOCl (oxidant) treatment. The acetate mass fraction in xanthan gum decreased by 42% and its pyruvate mass fraction increased by 63% as a result of HOCl treatment. The growth rate was almost unaffected by HOCl treatment. A hypothesis to explain the mechanism of xanthan gum overproduction by free-radical induction has been formulated. The significant aspects of the hypothesis, such as SoxS protein binding to the promoter region of the gum gene and the consequent increase in mRNA concentrations, have been experimentally verified.
authors.affiliation: Biochemical Engineering Group, Department of Chemical Engineering. Indian Institute of Technology, Bombay, Powai, Mumbai 400 076, India.
authors.forename: Y M
authors.initials: YM
authors.lastname: Rao
authors.forename: G K
authors.initials: GK
authors.lastname: Sureshkumar
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D019149:Bioreactors; D001709:Biotechnology / Q000379:methods; D004578:Electron Spin Resonance Spectroscopy; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics; D029968:Escherichia coli Proteins; D005609:Free Radicals; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006997:Hypochlorous Acid / Q000494:pharmacology*; D007700:Kinetics; D005810:Multigene Family; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D011401:Promoter Regions, Genetic; D015534:Trans-Activators; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D016959:Xanthomonas campestris / Q000187:drug effects / Q000235:genetics* / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D005609:Free Radicals; D011135:Polysaccharides, Bacterial; D015534:Trans-Activators; D014157:Transcription Factors; C070725:SoxS protein, E coli; D006997:Hypochlorous Acid; C002563:xanthan gum