Characterization of Electrical Current-Generation Capabilities from Thermophilic Bacterium Thermoanaerobacter pseudethanolicus Using Xylose, Glucose, Cellobiose, or Acetate with Fixed Anode Potentials

<i>Thermoanaerobacter pseudethanolicus</i> 39E (ATCC 33223), a thermophilic, Fe­(III)-reducing, and fermentative bacterium, was evaluated for its ability to produce current from four electron donorsxylose, glucose, cellobiose, and acetatewith a fixed anode potential (+ 0.042 V vs SHE) in a microbial electrochemical cell (MXC). Under thermophilic conditions (60 °C), <i>T. pseudethanolicus</i> produced high current densities from xylose (5.8 ± 2.4 A m^–2), glucose (4.3 ± 1.9 A m^–2), and cellobiose (5.2 ± 1.6 A m^–2). It produced insignificant current when grown with acetate, but consumed the acetate produced from sugar fermentation to produce electrical current. Low-scan cyclic voltammetry (LSCV) revealed a sigmoidal response with a midpoint potential of −0.17 V vs SHE. Coulombic efficiency (CE) varied by electron donor, with xylose at 34.8% ± 0.7%, glucose at 65.3% ± 1.0%, and cellobiose at 27.7% ± 1.5%. Anode respiration was sustained over a pH range of 5.4–8.3, with higher current densities observed at higher pH values. Scanning electron microscopy showed a well-developed biofilm of <i>T. pseudethanolicus</i> on the anode, and confocal laser scanning microscopy demonstrated a maximum biofilm thickness (<i>L</i>_f) greater than ∼150 μm for the glucose-fed biofilm