UV mutagenesis of Cupriavidus necator for extracellular production of (R)-3-hydroxybutyric acid.
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.
Ugwu
C U
CU
Institute of Life Sciences and Bioengineering, Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba City, Ibaraki, Japan.
Tokiwa
Y
Y
Aoyagi
H
H
Uchiyama
H
H
Tanaka
H
H
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
D020155:3-Hydroxybutyric Acid