Hyperthermiphile biofilms of Thermotoga neapolitana on different materials and electrostimulated: SEM micrographs and chemical data of the glucose fermentation in electrochemical reactors

Hyperthermophile bacteria were seldom investigated in bioelectrochemical systems although they allow more effective control of the inoculum in comparison with mesophilic bacteria. Biofilm formed in hyperthermophilic conditions (>60 °C) also rarely was documented (d'Ippolito et al., 2020; Belkin et al., 1986, Pysz et al., 2004). Scanning Electron Microscopy (SEM) micrographs documenting biofilms formed by the Hyperthermophile bacterium Thermotoga neapolitana on different solid materials (ceramic carrier, stainless steel mesh, carbon felt, carbon paper, expanse graphite, and carbon cloth) are shown in this report. Also, micrographs of the biofilm formed on electrodes of carbon cloth under a dynamic polarization oscillating around ±1 V (±0.8 V and ±1.2 V) are reported. Two procedures of sample preparation for SEM analyses are described and used: 1) a fast drying of samples, which is enough to underline the biofilm shape that covers solids, and 2) a chemical treating of the samples with glutaraldehyde, which better preserves the shape of bacterial cell components in the biofilm, although this treatment might cause the detachment of pieces of the biofilm. The different effect of potentiostatic and potentiodynamic polarizations on the glucose metabolism of T. neapolitana has been screened and discussed in the associated article [1]. Here, data of Optical Densities (O.D.) of culture media are provided, indicating the presence or absence of bacteria growth in the bulk of the media. Data have been collected every 24 h from the differently polarized bioreactors. The electrodes set-up of small bioreactors is also illustrated. Chemical data, optical data and SEM images, accordingly, document a retard in the glucose fermentation process due to a settlement of T. Neapolitana in a stationary phase. The polarization of electrodes can modify the stationary condition, inducing a possible change of the bacteria metabolism.