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

Thermoanaerobacter pseudethanolicus 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 degrees C), T. pseudethanolicus 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 T. pseudethanolicus on the anode, and confocal laser scanning microscopy demonstrated a maximum biofilm thickness (L-f) greater than similar to 150 mu m for the glucose-fed biofilm.