Surface analysis reveals biogenic oxidation of sub-bituminous coal by Pseudomonas fluorescens

Direct analysis of the colonised surface on coal using attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR) revealed the nature of bacteria-mediated oxidation at the coal surface. Unique oxidation peaks generated by the presence of Pseudomonas fluorescens on coal was shown through ATR-FTIR measurements, and ATR-FTIR imaging illustrated that this peak was only observed within the region of coal colonised by bacteria. Contact angle measurements and surface free energy of adhesion calculations showed that the adhesion between P. fluorescens and coal was thermodynamically favourable, and scanning electron microscopy (SEM) exhibited individual cell or monolayer cluster attachment on coal. Furthermore, Gaussian peak fitting of peroxidase-treated coal ATR-FTIR spectra revealed that peroxidase or related enzymes produced by P. fluorescens may be responsible for coal oxidation. This study demonstrated the usefulness and practicality of ATR-FTIR for analysing coal oxidation by P. fluorescens and may well be applied to other microbe-driven modifications of coal for its rapidity and reliability.