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Decrease of citric acid produced by Aspergillus niger through disruption of the gene encoding a putative
Kohtaro Kirimura1, Keiichi Kobayashi1, Isato Yoshioka1
1a Department of Applied Chemistry, Faculty of Science and Engineering , Waseda University , Tokyo , Japan.
Bioscience, Biotechnology, and Biochemistry
|February 6, 2019
Summary
The citrate-oxoglutarate shuttle protein, encoded by the cocA gene, is crucial for citric acid (CA) production in Aspergillus niger. Disrupting cocA significantly reduces CA yield, highlighting its role in microbial organic acid fermentation.
Area of Science:
- Biochemistry
- Molecular Biology
- Microbial Biotechnology
Background:
- Citric acid (CA) production in *Aspergillus niger* relies on efficient transport of CA from mitochondria to the cytosol.
- Identifying key genes involved in this transport is essential for optimizing CA fermentation.
Purpose of the Study:
- To clone and identify the gene responsible for mitochondrial citrate export in *A. niger*.
- To elucidate the role of this gene in citric acid production through gene disruption and complementation.
Main Methods:
- Gene cloning and identification of *cocA* in *A. niger* WU-2223L.
- Construction and characterization of *cocA* disruptant strains.
- Complementation studies to validate gene function.
Main Results:
- The *cocA* gene encodes a putative mitochondrial citrate-oxoglutarate shuttle protein.
- A *cocA* disruptant produced significantly less CA (35 g/L) compared to the wild-type strain (63 g/L) after 12 days.
- Complementation of the disruptant restored wild-type CA production levels and phenotypes.
Conclusions:
- The *cocA* gene and its protein product are critical for substantial citric acid production in *A. niger*.
- This finding provides significant insight into the mechanisms of microbial organic acid production via fermentation.
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