4. Conclusion
P. putida F1 was successfully preloaded onto CCFs and applied for airborne toluene degradation. Studies showed that the P. putidaF1 was able to grow on the CCF support and eventually formed mature biofilms under feeding with gaseous toluene. The CCF-supported P. putida F1 biofilms can grow at the RH range from 40 to 80% and the biomass grow faster at higher humidity levels. The optimal specific growth rate of P. putida F1 in gas phase was actually comparable to that in liquid phase. The CCF-supported P. putida F1 enable both growth-associated and non-growth associated biodegradation activities. Operated without any bulk liquid medium phase, the biofilm achieved direct degradation of gas phase VOC at rates of about one-order of magnitude higher than what has been previously reported for liquid culturing or immobilized cells. These results suggest that liquid phase mass transfer is a significant limiting factor for traditional biodegradation reactions, and biofilms operated in gas phases can promote efficient substrate-cell interactions and thus intensifying biotransformation reactions.