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A microfluidic system was developed to study the metabolic activity of a Geobacter sulfurreducens biofilm, identifying bottlenecks in electron transfer through extracellular cytochromes as a major metabolic bottleneck.

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Abstract

Abstract To target development of bioelectrochemical systems, we developed an advanced microfluidic method to identify reaction bottlenecks in the metabolic activity of a pure‐culture Geobacter sulfurreducens electroactive biofilm (EAB). The microfluidic system was devised to include perpendicular flow orientation for improved boundary layer uniformity and was combined with an embedded 3‐electrode system to accurately apply a constant potential during the entire experimental duration which lasted se. A 3‐sensor temperature control system provided the basis of accurate temperature pulsing, which modified the EAB metabolic activity over short time intervals relative to the bacterial doubling rate. The system, together with the unique ability to control hydrodynamic, electrochemical, and thermal conditions, was used as the basis for an Arrhenius approach to obtain activation energy barrier values at different growth times, acetate concentrations, and flow rates. The results indicated that bottlenecks in the overall metabolic activity after 1 month of growth time were related to electron transfer through extracellular cytochrome c. After the EAB further matured to 4 months old, the bottleneck appeared to switch to enzyme‐driven acetate oxidation. Based on this hypothesis, we observed after 4‐months, that strong increases in effective enzyme concentration were primarily obtained by increasing flow rate, and secondarily by increasing acetate concentration

Key findings

  • Electron transfer through extracellular cytochromes is a major metabolic bottleneck in Geobacter sulfurreducens biofilms.
  • The Arrhenius equation was used to determine activation energy barrier values at different growth times, acetate concentrations, and flow rates.
  • The results indicate that metabolic bottlenecks are related to electron transfer and are influenced by temperature, substrate concentration, and flow rate.

Keywords

Geobacter sulfurreducensArrhenius equationMicrofluidicsElectrochemistryActivation energyBiological system

Identifiers

DOI
10.1002/cctc.202401102
Journal
ChemCatChem
Year
2024