Diffusion coefficients of metabolites in active biofilms

Area of Science:

• Biochemistry
• Microbiology
• Chemical Engineering

Background:

• Diffusion coefficients are crucial for understanding metabolite transport in biofilms.
• Accurate measurement in active biofilms is challenging due to microbial activity.
• Existing methods often require detailed knowledge of microbial kinetics.

Purpose of the Study:

• To develop a new concept for determining diffusion coefficients in active biofilms.
• To establish conditions for constant microbial biofilm activity.
• To validate the method using oxygen and glucose diffusion in immobilized microbial systems.

Main Methods:

• Applying a concept based on constant local activity within the biofilm.
• Monitoring concentration steps with a microelectrode inside the biofilm.
• Calculating diffusion coefficients without prior knowledge of microbial kinetics.
• Formulating conditions using Thiele modulus and bulk substrate concentration.

Main Results:

• Successfully determined diffusion coefficients for oxygen and glucose in immobilized microbial systems.
• Demonstrated that concentration steps transmit unattenuated under constant activity.
• Observed that oxygen diffusion was more affected by immobilized cells than glucose due to partitioning.

Conclusions:

• The proposed method provides a reliable way to measure diffusion coefficients in active biofilms.
• Constant microbial activity is a key condition for simplified diffusion measurements.
• Solute partitioning between microbial cells and the aqueous phase influences diffusion dynamics.