Native and modified lactate dehydrogenase expression in a fumaric acid producing isolate Rhizopus oryzae 99-880

Curr Genet. 2007 Jul;52(1):23-33. doi: 10.1007/s00294-007-0135-0. Epub 2007 Jun 6.


Rhizopus oryzae is subdivided into two groups based on genetic and phenotypic differences. Type-I isolates accumulate primarily lactic acid when grown in the presence of a fermentable carbon source and contain two lactate dehydrogenase genes, ldhA and ldhB. Type-II isolates synthesize predominantly fumaric acid and only have an ldhB gene. In this study, we determined that ldhB transcript is only minimally expressed in the Type-II isolate R. oryzae 99-880. LdhB enzyme purified from gene clones isolated from the Type-I isolate R. oryzae NRRL 395 and the Type-II isolate R. oryzae 99-880 each showed reductive LDH activity (pyruvate to lactate), while no oxidative LDH activity (lactate to pyruvate) was detected in either preparation. A transformation system was then developed for the first time with R. oryzae 99-880, using a uracil auxotrophic isolate that could be complemented with an orotate phosphoribosyltransferase gene, pyrF, isolated in this study. Transformation of this Type-II isolate with the ldhA gene from R. oryzae NRRL 395 resulted in reductive LDH activity between 1.0 and 1.8 U/mg total protein. Additionally, transformed isolates grown with glucose accumulated up to 27 g lactic acid/l with a concurrent decrease in fumaric acid, ethanol, and glycerol compared with the untransformed and vector-transformed control strains.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • DNA, Fungal / isolation & purification
  • Fumarates / metabolism*
  • Glucose / metabolism
  • Isoenzymes / genetics
  • Isoenzymes / metabolism
  • L-Lactate Dehydrogenase / genetics
  • L-Lactate Dehydrogenase / metabolism*
  • Lactate Dehydrogenase 5
  • Lactic Acid / metabolism
  • Orotate Phosphoribosyltransferase / metabolism
  • Plasmids
  • RNA, Messenger / analysis
  • Recombination, Genetic
  • Rhizopus / enzymology*
  • Rhizopus / genetics
  • Transcription, Genetic
  • Transformation, Genetic


  • DNA, Fungal
  • Fumarates
  • Isoenzymes
  • RNA, Messenger
  • Lactic Acid
  • fumaric acid
  • L-Lactate Dehydrogenase
  • Lactate Dehydrogenase 5
  • lactate dehydrogenase 1
  • Orotate Phosphoribosyltransferase
  • Glucose