Effect of trace elements on citric acid fermentation by Aspergillus niger

Area of Science:

• Biotechnology
• Industrial Microbiology
• Biochemical Engineering

Background:

• Citric acid is a vital organic acid with widespread industrial applications.
• Optimizing microbial fermentation processes is crucial for efficient citric acid production.
• Aspergillus niger is a key microorganism for industrial citric acid biosynthesis.

Purpose of the Study:

• To determine the optimal conditions for citric acid production using a mutant strain of Aspergillus niger.
• To evaluate the efficiency of different carbon sources for citric acid fermentation.
• To identify key parameters influencing high yield citric acid fermentation.

Main Methods:

• Utilized a mutant strain (UV-ET-71-15) of Aspergillus niger for fermentation studies.
• Employed shaker flasks with a specifically formulated resin-treated sucrose medium.
• Investigated the impact of various parameters including medium composition, pH, temperature, inoculum, agitation, and fermentation time.

Main Results:

• Achieved a maximum citric acid yield of 98.7% on a sugar consumption basis in shaker flasks.
• Demonstrated successful fermentation using resin-treated clarified syrup (75% yield) and blackstrap molasses (68% yield).
• Identified optimal fermentation conditions: 3% inoculum, pH 4.5, 30°C, 250 rev/min agitation, and 8 days fermentation time.

Conclusions:

• The mutant strain UV-ET-71-15 of Aspergillus niger is highly efficient for citric acid production.
• Optimized medium composition and fermentation parameters significantly enhance citric acid yields.
• The mutant exhibits tolerance to high concentrations of trace elements, suggesting robustness in industrial settings.