Continuous ethanol production by flocculating yeast in the fluidized bed bioreactor

Area of Science:

• Biotechnology
• Biochemical Engineering
• Industrial Microbiology

Background:

• Continuous fermentation processes are crucial for efficient ethanol production.
• Saccharomyces cerevisiae is a key microorganism in industrial fermentation.
• Fluidized-bed bioreactors offer advantages for cell retention and high cell densities.

Purpose of the Study:

• To investigate continuous fermentation of Saccharomyces cerevisiae in a tower fluidized-bed bioreactor.
• To evaluate the impact of dilution rates on ethanol productivity and cell density.
• To assess the role of aeration in maintaining yeast viability and bioreactor operation.

Main Methods:

• Utilized a highly flocculant Saccharomyces cerevisiae strain.
• Conducted continuous fermentation in a tower fluidized-bed bioreactor.
• Employed synthetic and molasses media with 17% sugar concentration.
• Tested various dilution rates and aeration conditions.

Main Results:

• Achieved stable cell densities of 50 kg m-3 (dry weight) across tested dilution rates.
• Demonstrated a linear increase in ethanol productivity with dilution rates, reaching 15-20 kg m-3 h-1.
• Confirmed that aeration stabilized yeast flocculating activity and viability.
• Enabled long-term, stable operation of the bioreactor.

Conclusions:

• Tower fluidized-bed bioreactors are effective for continuous ethanol fermentation with Saccharomyces cerevisiae.
• Optimizing dilution rates and employing aeration are key for maximizing ethanol productivity and process stability.
• Aeration is critical for maintaining yeast performance and enabling sustained bioreactor operation.