High-cell-density fermentation for ergosterol production by Saccharomyces cerevisiae

Area of Science:

• Biotechnology
• Industrial Microbiology
• Metabolic Engineering

Background:

• Ergosterol is a vital sterol in yeast cell membranes.
• High-cell-density fermentation is crucial for efficient ergosterol production.
• Optimizing fermentation parameters is key to maximizing ergosterol yield.

Purpose of the Study:

• To investigate direct feedback control of glucose using on-line ethanol monitoring for ergosterol production.
• To analyze key fermentation parameters influencing ergosterol yield.
• To establish effective fed-batch strategies for high-cell-density fermentation.

Main Methods:

• Utilized on-line ethanol concentration monitoring for direct glucose feedback control.
• Implemented fed-batch strategies controlling glucose feeding rate based on ethanol concentration.
• Adjusted pH using ammonia and monitored parameters like dissolved oxygen and respiratory quotient (RQ).

Main Results:

• Achieved a yeast dry weight of 120 g/l and an ergosterol yield of 1500 mg/l.
• Demonstrated that controlling ethanol concentration below 1% and maintaining RQ at approximately 1.0 were effective.
• Fermentation parameters successfully described the overall fermentation process dynamics.

Conclusions:

• Direct feedback control of glucose based on ethanol concentration is an effective strategy for ergosterol production.
• Optimized fermentation conditions (30°C, pH 5.5, 600 rpm, 60 h) significantly enhance ergosterol yield.
• This approach provides a robust method for high-cell-density ergosterol production.