[Improving ergosterol production from molasses by Saccharomyces cerevisiae]

Area of Science:

• Biotechnology
• Microbial Fermentation
• Metabolic Engineering

Background:

• Ergosterol is a vital yeast metabolite with significant economic value.
• Saccharomyces cerevisiae is a key organism for ergosterol production.
• Molasses presents a cost-effective and sustainable substrate for yeast fermentation.

Purpose of the Study:

• To enhance ergosterol production by Saccharomyces cerevisiae YEH56 (pHXA42) using molasses.
• To optimize fermentation medium composition and conditions for maximal ergosterol yield.
• To evaluate the effectiveness of different fermentation strategies, including pH control and feeding, in a bioreactor setting.

Main Methods:

• Statistical experimental designs (Plackett-Burman and central composite) were employed to identify optimal fermentation medium components.
• Shake-flask cultures were used to determine initial ergosterol yields with the optimized medium.
• A 5-L bioreactor was utilized to implement pH-controlled fermentation and molasses feeding strategies.
• Ergosterol yield and production rate were measured as key performance indicators.

Main Results:

• The optimized fermentation medium increased ergosterol yield by 29.5% in shake-flask cultures.
• A pH-control strategy in a bioreactor resulted in a 62.1% increase in ergosterol yield.
• Molasses feeding strategy further boosted ergosterol yield to 1,953.85 mg/L, a 3.2-fold increase over batch fermentation.
• Ergosterol production rate improved by 42.7% with the feeding strategy.

Conclusions:

• Optimized fermentation medium and advanced bioreactor strategies significantly enhance ergosterol production in Saccharomyces cerevisiae.
• The combination of pH control and molasses feeding is highly effective for maximizing ergosterol yield and production rate.
• This study demonstrates a scalable and efficient method for producing ergosterol from molasses, improving its industrial viability.