Isolation and Characterization of a Bacterial Population from a Biofilter Treating Waste Gases

Biofiltration units are microbial ecosystems for the treatment of low-concentration, biodegradable waste gases. The aim of this work was to isolate and characterize an appropriate microbial culture for inoculation of a rockwool biofilter that treats waste gases from a fast-food restaurant using rape-seed oil in its frying process. Batch cultures from three various bacterial sources were studied under different chemical and physical conditions and compared to the growth of Bacillus sp. All cultures were able to degrade rape-seed oil and its oxidation products, with a simultaneous pH decrease in the batch cultures. It was necessary to add a salt medium containing, for example, phosphorus and nitrogen to obtain maximum growth. An exponential growth phase during a period of 3 to 8 days, with generation times of 9 to 33 h, was followed by slower growth. After a stationary phase of 25 to 40 days, the bacterial number started to decrease, probably due to substrate and/or oxygen depletion, or unfavorable pH. The rockwool biofilter material did not inhibit the growth of the bacterial cultures, and seemed to have a buffering capacity, which could prevent acidification of a future biofilter. The isolated bacteria from the mixed culture were found to be mesophilic, aerobic, Gram-negative rods.