Diversity of the microflora of a compost-packed biofilter treating benzene-contaminated air

摘要

A laboratory scale compost-packed upflow biofilter was fluxed with benzene contaminated air over a period of 240 days with a progressive increase of concentration, resulting in an efficiency of benzene removal of 95-100%. Samples of compost from different depths of the biofiltering column were analysed for total bacterial counts and eubacterial diversity with ARISA fingerprinting, showing that the treatment established a rich bacterial community adapted to increasing benzene concentrations. Identification of the strains cultured from the compost showed that besides low G + C Gram positives and actinomycetes, typical of compost, during the treatment new strains appeared, belonging to β- and γ-proteobacteria, and high G + C Gram+. Among benzene-degraders strains affiliated to Neisseria and Bordetella genera known to include pathogenic species were identified. 37.5% of the strains were able to use benzene as a substrate, and several resulted to have a toluene dioxygenase-like gene. Several peaks of cultivatable benzene users, mainly represented by Rhodococcus sp. were present in the ARISA fingerprint, which described the total bacterial diversity of the biofilter, showing that they constituted a significant part of the microflora.