Microbial succession in a compost-packed biofilter treating benzene-contaminated air.
Air artificially contaminated with increasing concentrations of benzene was treated in a laboratory scale compost-packed biofilter for 240 days with a removal efficiency of 81-100%. The bacterial community in the packing material (PM) at different heights of the biofilter was analysed every 60 days. Bacterial plate counts and ribosomal intergenic spacer analysis (RISA) of the isolated strains showed that the number of cultivable aerobic heterotrophic bacteria and the species diversity increased with benzene availability. Identification of the isolated species and the main bands in denaturing gradient gel electrophoresis (DGGE) profiles from total compost DNA during the treatment revealed that, at a relatively low volumetric benzene load (1.2< or =VBL< or =6.4 g m(-3) (PM) h(-1)), besides low G+C Gram positive bacteria, originally present in the packing compost, bacteroidetes and beta- and gamma-proteobacteria became detectable in the colonising population. At the VBL value (24.8 g m(-3) (PM) h(-1)) ensuring the maximum elimination capacity of the biofilter (20.1 g m(-3) (PM) h(-1)), strains affiliated to the genus Rhodococcus dominated the microflora, followed by beta-proteobacteria comprising the genera Bordetella and Neisseria. Under these conditions, more than 35% of the isolated strains were able to grow on benzene as the sole carbon source. Comparison of DGGE and automated RISA profiles of the total community and isolated strains showed that a complex bacterial succession occurred in the reactor in response to the increasing concentrations of the pollutant and that cultivable bacteria played a major role in benzene degradation under the adopted conditions.
Borin
Sara
S
Dipartimento di Scienze e Tecnologie Alimentari e Microbiologiche, Università degli Studi di Milano, Milano, Italy.
Marzorati
Massimo
M
Brusetti
Lorenzo
L
Zilli
Mario
M
Cherif
Hanene
H
Hassen
Abdennaceur
A
Converti
Attilio
A
Sorlini
Claudia
C
Daffonchio
Daniele
D
D000393:Air Pollutants / Q000378:metabolism*; D001554:Benzene / Q000378:metabolism*; D020562:Betaproteobacteria / Q000235:genetics / Q000378:metabolism; D001673:Biodegradation, Environmental; D004275:DNA, Ribosomal / Q000235:genetics; D015180:Electrophoresis, Gel, Two-Dimensional / Q000379:methods; D005374:Filtration; D007218:Industrial Microbiology / Q000295:instrumentation / Q000379:methods*; D012240:Rhodococcus / Q000235:genetics / Q000378:metabolism; D012987:Soil
D000393:Air Pollutants; D004275:DNA, Ribosomal; D012987:Soil; D001554:Benzene