DIVERSITY OF PAH-DEGRADING BACTERIA IN AN AIRLIFT-SUSPENSION REACTOR SYSTEM FOR WASTE-WATER CLEANING

Different samples from a reactor system for the cleaning of an emulsif ied waste oil containing approximately 1% of different polycyclic arom atic hydrocarbons (PAH) were studied for the diversity of phenanthrene , anthracene, and acenaphthene-metabolizing bacteria. From more than 2 8 different taxa found in the airlift-suspension reactor, nine were ab le to mineralize at least one of the PAH, belonging to the genera Baci llus, Mycobacterium, Nocardia, Sphingomonas, Alcaligenes, Pseudomonas, and the Flavobacterium/Cytophaga group. In the sludge from the thicke ner of the reactor system, a reduced number of metabolically active gr oups could be detected. The impact of different precultivation substra tes on the degradation capability was investigated with five PAH-degra ding bacterial strains. Four isolates were influenced by the precultiv ation substrates, however, one isolate (Alcaligenes-like) as well as t he mixture of the five strains showed no changes in their degradation capability. The results indicated a strong impact of the precultivatio n methods on the composition of bacterial communities and the activity and the degradation characteristics of bacteria with respect to diffe rent PAH.