The function of a toluene-degrading bacterial community in a waste gas trickling filter

The function of a community of toluene-degrading bacteria in a biofilm syst em was investigated with regard to growth and toluene degradation in order to investigate substrate interactions in the community. This was done by th e combination of experimental observations using a specific oligonucleotide 16S ribosomal RNA probe targeting the toluene-degrading species Pseudomona s putida, and by computer simulations (AQUASIM) of the biofilm growth based on a food web model. Biofilms were taken from a lab-scale trickling filter for treatment of toluene-polluted air. The biofilm growth and the activity of P. putida, a representative of the toluene-degrading species in the bio film which have been described previously (Pedersen et al., 1997) were simu lated. The simulation indicated that the volume fraction of the toluene deg raders in the biofilm decreased from 12% to only 2% (11% of dry weight) dur ing two weeks. In spite of the low fraction in the biofilm, the toluene deg raders supported growth of the dominating part of non-toluene-degrading het erotrophs in the biofilm, as toluene was the sole carbon source supplied to the system. The maximum intrinsic growth rate of P. putida in the biofilm was only 20% of the maximum growth rare determined in a batch experiment wi th suspended P. putida cells. (C) 1999 IAWQ Published by Elsevier Science L td. All rights reserved.