Deletion of a Chitin Synthase Gene in a Citric Acid Producing Strain of Aspergillus niger

Journal Article · Mon Jan 29 04:00:00 EST 2007 · Journal of Undergraduate Research, 7:138-139

OSTI ID:1020644

Rinker, Torri E; Baker, Scott E

Citric acid production by the filamentous fungus Aspergillus niger is carried out in a process that causes the organism to drastically alter its morphology. This altered morphology includes hyphal swelling and highly limited polar growth resulting in clumps of swollen cells that eventually aggregate into pellets of approximately 100 microns in diameter. In this pelleted form, A. niger has increased citric acid production as compared to growth in filamentous form. Chitin is a crucial component of the cell wall of filamentous fungi. Alterations in the deposition or production of chitin may have profound effects on the morphology of the organism. In order to study the role of chitin synthesis in pellet formation we have deleted a chitin synthase gene (csmA) in Aspergillus niger strain ATCC 11414 using a PCR based deletion construct. This class of chitin synthases is only found in filamentous fungi and is not present in yeasts. The csmA genes contain a myosin motor domain at the N-terminus and a chitin synthesis domain at the C-terminus. They are believed to contribute to the specialized polar growth observed in filamentous fungi that is lacking in yeasts. The csmA deletion strain (csmAΔ) was subjected to minimal media with and without osmotic stabilizers as well as tested in citric acid production media. Without osmotic stabilizers, the mutant germlings were abnormally swollen, primarily in the subapical regions, and contained large vacuoles. However, this swelling is ultimately not inhibitory to growth as the germlings are able to recover and undergo polar growth. Colony formation was largely unaffected in the absence of osmotic stabilizers. In citric acid production media csmAΔ was observed to have a 2.5 fold increase in citric acid production. The controlled expression of this class of chitin synthases may be useful for improving production of organic acids in filamentous fungi.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1020644
• Report Number(s): PNNL-SA-51517; BM0101020
• Journal Information: Journal of Undergraduate Research, 7:138-139, Journal Name: Journal of Undergraduate Research, 7:138-139 Vol. 7
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
99 GENERAL AND MISCELLANEOUS
ASPERGILLUS
Aspergillus niger
Bioproducts
CELL WALL
CHITIN
CITRIC ACID
COLONY FORMATION
Chitin Synthase
Citric acid
DEPOSITION
FUNGI
Fungi
GENES
MORPHOLOGY
MOTORS
MUTANTS
MYOSIN
NIGER
ORGANIC ACIDS
PELLETS
PRODUCTION
STRAINS
SWELLING
SYNTHESIS
YEASTS