Microbial composition and structure of a multispecies biofilm from a trickle‐bed reactor used for the removal of volatile aromatic hydrocarbons from a waste gas

The microbial composition and structure of a multispecies biofilm of a laboratory‐scale trickle‐bed bioreactor for the treatment of waste gas was examined. The model pollutant was a volatile organic compound‐mixture of polyalkylated benzenes called Solvesso 100 ® . Fluorescent in‐situ hybridization (FISH) and confocal laser scanning microscopy (CLSM) were applied. Two new Solvesso 100 ® ‐degrading Pseudomonas sp strains were isolated from the multispecies biofilm. Corresponding isolate‐specific oligonucleotide probes were designed and applied successfully. A major finding was that the fraction of Solvesso 100 ® ‐degrading bacteria in the biofilm was low (about 3–6% during long‐term operation). The majority of the active cells were saprophytes which utilized intermediates and cell lysis products. The measured fraction of extracellular polymeric substances of the mature biofilm was 89–93% of the total biomass. The CLSM examinations of a 3‐days‐old approx 10 µm thick biofilm revealed highly heterogeneous structures with distinguished three‐dimensional matrix‐enclosed microcolony bodies spread across the substratum surface. The 28‐days‐old 80–960 µm thick biofilm exhibited voids, cell‐free channels, and pores of variable sizes. In both cases, an even distribution of active cells and pollutant‐degrading bacteria throughout the biofilm cross‐section as well as through the biofilm depth was observed. Copyright © 2003 Society of Chemical Industry