BACTERIAL COMMUNITY DYNAMICS DURING START-UP OF A TRICKLE-BED BIOREACTOR DEGRADING AROMATIC-COMPOUNDS

This study was performed with a laboratory-scale fixed-bed bioreactor degrading a mixture of aromatic compounds (Solvesso100), The starter c ulture for the bioreactor was prepared in a fermenter with a wastewate r sample of a car painting facility as the inoculum and Solvesso100 as the sole carbon source, The bacterial community dynamics in the ferme nter and the bioreactor were examined by a conventional isolation proc edure and in situ hybridization with fluorescently labeled rRNA-target ed oligonucleotides, Two significant shifts in the bacterial community structure could be demonstrated, The original inoculum from the waste water of the car factory was rich in proteobacteria of the alpha and b eta subclasses, while the final fermenter enrichment was dominated by bacteria closely related to Pseudomonas putida or Pseudomonas mendocin a, which both belong to the gamma subclass of the class Proteobacteria , A second significant shift was observed when the fermenter culture w as transferred as inoculum to the trickle-bed bioreactor, The communit y structure in the bioreactor gradually returned to a higher complexit y, with the dominance of beta and alpha subclass proteobacteria, where as the gamma subclass proteobacteria sharply declined. Obviously, the preceded pollutant adaptant did not lead to a significant enrichment o f bacteria that finally dominated in the trickle-bed bioreactor, In th e course of experiments, three new 16S as well as 23S rRNA-targeted pr obes for beta subclass proteobacteria were designed, probe SUBU1237 fo r the genera Burkholderia and Sutterella, probe ALBO34a for the genera Alcaligenes and Bordetella, and probe Bcv13b for Burkholderia cepacia and Burkholderia vietnamiensis, Bacteria hybridizing,vith the probe B cv13b represented the main Solvesso100-degrading population in the rea ctor.