Hydrocarbon degrading bacteria vs microbial consortia in the degradation of Policyclic Aromatic Hydrocarbons

Abstract

The Harbor of Priolo Gargallo is a chronically polluted area in Sicily (Italy). Bioremediation is an alternative friendly strategy to reduce environmental risks that relies on microorganisms that play a key role in the biodegradation of hydrocarbon contaminants. In this study, sediment samples were collected in 6 stations inside the area indicated. Analysis of total hydrocarbons, microbial abundance (DAPI, CFU and MPN), and total bacterial diversity (DGGE) were carried out. Enrichment cultures and isolation of hydrocarbon-degrading bacteria were carried out in the mineral medium ONR7a with a mix of Polycyclic Aromatic Hydrocarbons [PAHs-Mix; Methylnaphtalene, Byphenile, Phenantrene, Dibenzothiophene, Pyrene, Benzo(α) pyrene, final concentration 60 ppm]. A total of 77 isolates were obtained from enrichments. 74 isolates were identified by taxonomic 16S rDNA analysis and were affiliated to mainly obligate hydrocarbonoclastic bacterial genera (e.g. Alcanivorax) and to genera of generalist HC-degraders (e.g. Vibrio, Thalassospira, Marinobacter, Rhodococcus, Pseudomonas, Roseovarius). The object of this study was the selection of a microbial isolate/consortium with better efficiency in the degradation of PAHs. Therefore, 7 hydrocarbon degrading bacteria and 2 microbial consortia were selected, and incubated in ONR7a mineral medium with PAHs – Mix at 25° in a shaker for 10 days. At the end the results of degradation of PAHs Mix showed better efficiency in the microbial consortia in respect to the single isolates.