Promoter engineering with programmable upstream activating sequences in Aspergillus Niger cell factory.

Area of Science:

• Molecular Biology
• Metabolic Engineering
• Industrial Biotechnology

Background:

• Aspergillus niger is a key industrial fungus for producing organic acids and enzymes.
• Precise control over gene expression, especially using strong promoters, is crucial for optimizing yields in A. niger.
• Limited knowledge of promoter function hinders efficient strain engineering in A. niger.

Purpose of the Study:

• To construct and characterize a synthetic promoter library for fine-tuning gene expression in A. niger.
• To identify and utilize functional upstream activation sequences (UAS) to enhance promoter strength.
• To apply the synthetic promoter library to improve citric acid production in A. niger.

Main Methods:

• Identification of two functional upstream activation sequences (UAS) in A. niger.
• Construction of a synthetic promoter library by combining UAS elements with the PgpdA promoter.
• Characterization of promoter activity and application in regulating cexA expression for citric acid production.

Main Results:

• A synthetic promoter library with a wide dynamic range was successfully created.
• The strongest synthetic promoter showed 5.4-fold higher activity than previously reported strong promoters.
• Citric acid production increased by 1.6-2.3 fold, reaching a maximum titer of 145.3 g/L.

Conclusions:

• The synthetic promoter library is an effective tool for precise transcriptional control in A. niger.
• Promoter engineering holds significant potential for improving fungal cell factories.
• This approach enables enhanced yields of valuable compounds in industrial fermentation.