Improvement in citric acid production by haploidization of Aspergillus niger diploid strains

Kohtaro Kirimura, Pyo Lee Sung Pyo Lee, Iwao Nakajima, Seiichiro Kawabe, Shoji Usami*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

46 Citations (Scopus)


Segregation of diploid strains by a haploidizing agent was used to improve citric acid producing strains of Aspergillus niger. Stable diploid strains were obtained via protoplast fusion between two citric acid-producing strains from different genealogies, one for shaking culture and the other for solid culture. Diploid strains were treated by benomyl as a haploidizing agent, and many segregants were obtained. Prototrophic segregants were selected and their haploidy was confirmed by their conidial size and DNA contents. The prototrophic segregants were very variable in their citric acid productivities, some of them better either in shaking culture or in solid culture than both the parental strains. The presence of methanol stimulated citric acid production by the parental and the diploid strains. However, all prototrophic segregants derived from one diploid strain had higher productivities in solid cultures without methanol than in those with methanol.

Original languageEnglish
Pages (from-to)375-382
Number of pages8
JournalJournal of Fermentation Technology
Issue number4
Publication statusPublished - 1988


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