Community fingerprinting of dominant populations in hydrogen-producing bioreactors

Biological H₂ production in engineered reactors was studied and the microbial communities responsible by molecular biology techniques were characterized. Ribosomal intergenic spacer analysis (RISA) fingerprints were obtained from bacterial communities in continuous-flow bioreactors inoculated with heat-treated soil and operated at 30° and 37°C. DNA bands from fingerprints consistently yielded Clostridia spp. belonging to Cluster I (Stackebrandt and Hippe, 2001). Subcluster Ib populations were closely related to the solventogenic Clostridium acetobutylicum and Ic populations to C. acidisoli, an acid-tolerant isolate from forest litter. Using subsamples of the same heat-treated soil inoculum, independent reactor trials exhibited different N₂ production rates and efficiencies when glucose concentrations were from 1-10 g/L. Only populations belonging to Clostridiaceae were detected in all RISA fingerprints. Clostridium acidisoli relatives (Cluster Ic clostridia} were detected with greatest frequency at lower glucose concentrations, while Cluster Ib clostridia were most frequently detected at higher glucose concentrations. This is an abstract of a paper presented at the 228th ACS National Meeting (Philadelphia, PA 8/22-26/2004).