Relationship between energy substrate utilization and specific growth rate in Aspergillus nidulans

Area of Science:

• Microbiology
• Biochemistry

Background:

• Understanding microbial metabolism is crucial for industrial biotechnology.
• Aspergillus nidulans is a model organism for fungal research.
• Accurate determination of maintenance coefficients is essential for optimizing fungal growth.

Purpose of the Study:

• To determine the maintenance coefficients for glucose and oxygen in Aspergillus nidulans chemostat cultures.
• To investigate the impact of melanin production on biomass calculations.
• To explore the relationship between growth rate, substrate utilization, and enzyme activity.

Main Methods:

• Chemostat cultivation of Aspergillus nidulans at 30°C.
• Measurement of glucose and oxygen consumption rates.
• Determination of dry weight and melanin content.
• Assay of specific enzyme activities at different growth rates.

Main Results:

• Approximate maintenance coefficients for glucose and oxygen were determined.
• Biomass-corrected maintenance coefficient for glucose was calculated.
• A nonlinear relationship between growth rate and glucose utilization was observed at high growth rates.
• Oxidative capacity increased with growth rate, suggesting enhanced enzyme synthesis.
• Reduced nicotinamide adenine dinucleotide phosphate: (acceptor) oxido-reductase activities were highest at low growth rates.

Conclusions:

• Melanin production complicates direct dry weight measurements for maintenance coefficient calculations.
• Metabolic activity in Aspergillus nidulans undergoes a qualitative change at high growth rates.
• Enzyme synthesis is upregulated at higher growth rates, except for specific oxido-reductases.