title: UV mutagenesis of Cupriavidus necator for extracellular production of (R)-3-hydroxybutyric acid.
abstract: OBJECTIVE
  Ultraviolet (UV) mutagenesis was carried out to obtain mutant strains of Cupriavidus necator that could produce (R)-3-hydroxybutyric acid [(R)-3-HB] in the culture supernatant.
  
  
  RESULTS
  C. necator (formerly known as Ralstonia eutropha) was subjected to UV radiation to generate mutants that are capable of producing (R)-3-HB in the culture supernatant. Results indicated that UV mutagen disrupted the phbB (phbB knock-out) and thus, promoted production of (R)-3-HB in mutant strains. Inclusion of acetoacetate esters (carbonyl compounds) in the culture broth led to increased production of (R)-3-HB. Thus, acetoacetyl-CoA (an intermediate of the PHB synthetic pathway) might have been converted to acetoacetate, which in the presence of (R)-3-HB dehydrogenase and NADPH/NADP(+), resulted in extracellular production of (R)-3-HB.
  
  
  CONCLUSIONS
  UV mutagenesis proved to be a satisfactory method in generating interesting mutants for extracellular production of (R)-3-HB. Extracellular production of (R)-3-HB upon addition of acetoacetate esters would suggest a likely (R)-3-HB biosynthetic pathway in C. necator.
  
  
  CONCLUSIONS
  Mutants obtained in this study are very useful for production of (R)-3-HB. For the first time, the production of (R)-3-HB by C. necator via acetoacetate is reported.
authors.affiliation: Institute of Life Sciences and Bioengineering, Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba City, Ibaraki, Japan.
authors.forename: C U
authors.initials: CU
authors.lastname: Ugwu
authors.forename: Y
authors.initials: Y
authors.lastname: Tokiwa
authors.forename: H
authors.initials: H
authors.lastname: Aoyagi
authors.forename: H
authors.initials: H
authors.lastname: Uchiyama
authors.forename: H
authors.initials: H
authors.lastname: Tanaka
mesh_terms: D020155:3-Hydroxybutyric Acid / Q000032:analysis / Q000378:metabolism*; D019149:Bioreactors / Q000382:microbiology; D002851:Chromatography, High Pressure Liquid; D020118:Cupriavidus necator / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects*; D007218:Industrial Microbiology / Q000379:methods*; D016296:Mutagenesis; D013053:Spectrophotometry; D014466:Ultraviolet Rays
chemical_list: D020155:3-Hydroxybutyric Acid