Effects of substrate diffusion and anode potential on kinetic parameters for anode-respiring bacteria

Area of Science:

• Microbial electrochemistry
• Biofilm kinetics
• Renewable energy

Background:

• Anode-respiring bacteria (ARB) are crucial for microbial electrolysis/fuel cells, with their substrate-utilization rate directly influencing current density.
• Estimating kinetic parameters like half-maximum-rate concentration (K(s)) and maximum specific substrate-utilization rate (q(max)) is vital for optimizing microbial electrolysis cell performance.

Purpose of the Study:

• To evaluate the impact of substrate diffusion and anode potential on K(s) and q(max) estimations for a mixed-culture biofilm oxidizing acetate in a microbial electrolysis cell.
• To determine the intrinsic kinetic parameters and growth rates of ARB under specific conditions.

Main Methods:

• Utilized a mixed-culture biofilm in a microbial electrolysis cell fed with acetate.
• Analyzed the effects of varying substrate diffusion and anode potentials on kinetic parameter estimations.
• Determined intrinsic K(s), q(max), maximum specific growth rate (μ(max)), and half-saturation anode potential (E(KA)).

Main Results:

• The intrinsic K(s) was determined to be 119 g COD/m³, with substrate diffusion significantly affecting its estimation, while anode potential had a minor impact.
• The intrinsic q(max) was 22.3 g COD/g VS-d, with anode potential influencing q(max) but substrate diffusion having a negligible effect.
• A high maximum specific growth rate (μ(max)) of 3.2/d was observed, along with a very negative half-saturation anode potential (E(KA)) of -0.448 V (vs Ag/AgCl).

Conclusions:

• The studied ARB are fast growers with a low E(KA), minimizing anode potential limitations on current density and substrate utilization.
• Substrate diffusion is a key factor in accurately estimating K(s) for ARB biofilms.
• The findings provide critical insights for optimizing microbial electrolysis cell design and operation for efficient acetate oxidation.