Oxalic acid production by citric acid-producing Aspergillus niger overexpressing the oxaloacetate hydrolase gene oahA

Keiichi Kobayashi, Takasumi Hattori, Yuki Honda, Kohtaro Kirimura

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

The filamentous fungus Aspergillus niger is used worldwide in the industrial production of citric acid. However, under specific cultivation conditions, citric acid-producing strains of A. niger accumulate oxalic acid as a by-product. Oxalic acid is used as a chelator, detergent, or tanning agent. Here, we sought to develop oxalic acid hyperproducers using A. niger as a host. To generate oxalic acid hyperproducers by metabolic engineering, transformants overexpressing the oahA gene, encoding oxaloacetate hydrolase (OAH; EC 3.7.1.1), were constructed in citric acid-producing A. niger WU-2223L as a host. The oxalic acid production capacity of this strain was examined by cultivation of EOAH-1 under conditions appropriate for oxalic acid production with 30 g/l glucose as a carbon source. Under all the cultivation conditions tested, the amount of oxalic acid produced by EOAH-1, a representative oahA-overexpressing transformant, exceeded that produced by A. niger WU-2223L. A. niger WU-2223L and EOAH-1 produced 15.6 and 28.9 g/l oxalic acid, respectively, during the 12-day cultivation period. The yield of oxalic acid for EOAH-1 was 64.2 % of the maximum theoretical yield. Our method for oxalic acid production gave the highest yield of any study reported to date. Therefore, we succeeded in generating oxalic acid hyperproducers by overexpressing a single gene, i.e., oahA, in citric acid-producing A. niger as a host.

Original languageEnglish
Pages (from-to)749-756
Number of pages8
JournalJournal of Industrial Microbiology and Biotechnology
Volume41
Issue number5
DOIs
Publication statusPublished - 2014 May

Keywords

  • Aspergillus niger
  • Citric acid
  • Metabolic engineering
  • Oxalic acid production
  • Oxaloacetate hydrolase

ASJC Scopus subject areas

  • Biotechnology
  • Bioengineering
  • Applied Microbiology and Biotechnology

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