In industrial biotechnology, fermentation processes are used for the microbial conversion of organic substrates into target products such as ethanol, yeast, enzymes, organic acids or biogas.

Causes of Foam Formation in Fermentation Processes

The substrates used often contain carbohydrates, proteins, hydrolysates and ancillary components that are released or biochemically transformed during fermentation. In addition, microbial metabolism generates amino acids, proteins and cellular components that further intensify foam formation.

Additional foam-promoting factors include:

• Gas release (CO₂ in anaerobic processes)
• Air injection in aerobic fermentations
• High agitation intensity and shear forces
• Increasing biomass concentrations
• Changes in the viscosity of the medium

Different Foam Loads in Aerobic and Anaerobic Fermentation

In anaerobic processes (e.g. alcohol or biogas fermentation), foam formation is mainly caused by the release of CO₂ in combination with foam-active components present in the medium.

In aerobic fermentations (e.g. yeast, enzyme or antibiotic production), process air is introduced to supply oxygen. The resulting gas bubbles, together with proteins and biomass, lead to particularly stable foam structures. In practice, aerobic processes are therefore generally much more foam-intensive.

Defoamer Dosing

Without targeted foam control, fermentation processes may suffer from fermenter overflow, product losses, contamination and fouling of equipment. Modern fermentation plants therefore rely on demand-driven, automated defoamer dosing.

Typical dosing strategies include:

• Continuous or sensor-based addition
• Pre-dosing into the fermentation medium
• Demand-based re-dosing during critical process phases

Selection of Suitable Defoamers

For fermentation processes, defoamers are required that:

• Provide high defoaming efficiency at low dosage
• Do not inhibit microorganisms
• Have minimal impact on oxygen transfer
• Are compatible with process requirements and food regulations

KEBO defoamers for fermentation, such as KEBOSPUM HES, KEBOSPUM FES or KEBOSPUM FEZ, are specifically designed to meet these requirements. They support stable, controlled production conditions while ensuring high process yields. Please refer to our overview of the key defoamers.