Aeration strategy: a need for very high ethanol performance in Saccharomyces cerevisiae fed-batch process

Area of Science:

• Biotechnology
• Fermentation Science
• Metabolic Engineering

Background:

• Simultaneous management of growth and production is crucial for intensifying bio-fuel ethanol processes.
• High ethanol concentrations pose challenges for Saccharomyces cerevisiae fermentation kinetics.
• Aeration strategy is a key factor in optimizing yeast performance.

Purpose of the Study:

• To quantify the effect of aeration conditions (micro-aerobic vs. aerobic) on Saccharomyces cerevisiae behavior.
• To identify an optimal aeration strategy for intensifying bio-fuel ethanol production.
• To evaluate fermentation parameters and kinetics at high ethanol concentrations (up to 147 g/L).

Main Methods:

• Cultivation of Saccharomyces cerevisiae in very high ethanol performance fed-batch cultures.
• Comparison of oxygen-limited (micro-aerobic) versus non-limited (aerobic) aeration conditions.
• Quantification of fermentation parameters, kinetics, cell mass, and by-product formation.

Main Results:

• Aerobic cultures achieved higher ethanol titres (147 g/L vs. 131 g/L) and productivity (3.3 g/L/h vs. 2.6 g/L/h).
• Full aeration increased viable cell mass by 23% due to higher growth rate and yield, with reduced ethanol inhibition.
• Glycerol production, a major by-product, was significantly reduced from 12 g/L to 4 g/L under aerobic conditions.

Conclusions:

• Aeration strategy is a critical determinant for achieving highly competitive, very high ethanol performance.
• Non-limited oxygen supply optimizes Saccharomyces cerevisiae fermentation for increased ethanol yield and reduced by-products.
• Aeration management is as important as vitamin feeding for maximizing ethanol production efficiency.