TOLUENE DEGRADATION KINETICS FOR PLANKTONIC AND BIOFILM-GROWN CELLS OF PSEUDOMONAS-PUTIDA 54G

Toluene degradation kinetics by biofilm and planktonic cells of Pseudo monas putida 54G were compared in this study. Batch degradation of C-1 4 toluene was used to evaluate kinetic parameters for planktonic cells . The kinetic parameters determined for toluene degradation were: spec ific growth rate, mu max = 10.08 +/- 1.2/day; half-saturation constant , K-s = 3.98 +/- 1.28 mg/L; substrate inhibition constant, K-I = 42.78 +/- 3.87 mg/L. Biofilm cells, grown on ceramic rings in vapor phase b ioreactors, were removed and suspended in batch cultures to calculate C-14 toluene degradation rates. Specific activities measured for plank tonic and biofilm cells were similar based on toluene degrading cells and total biomass. Long-term toluene exposure reduced specific activit ies that were based on total biomass for both biofilm and planktonic c ells. These results suggest that long-term toluene exposure caused a l arge portion of the biomass to become inactive, even though the biofil m was not substrate limited. Conversely, specific activities based on numbers of totuene-culturable cells were comparable for both biofilm a nd planktonically grown cultures. Planktonic cell kinetics are often u sed in bioreactor models to model substrate degradation and growth of bacteria in biofilms, a procedure we found to be appropriate for this organism. For superior bioreactor design, however, changes in cellular activity that occur during biofilm development should be investigated under conditions relevant to reactor operation before predictive mode ls for bioreactor systems are developed. (C) 1997 John Wiley & Sons, i nc.