Étude de la biodégradation de composés phénoliques par le microbiote des effluents de la raffinerie de pétrole de Skikda.

Abstract

This study was conducted to evaluate the capacity of microorganisms present in wastewater from an oil refinery (Sonatrach, Skikda / Algeria) to degrade (alkyl)phenols; a collection of bacterial strains has been obtained, some of which may also degrade other aromatic compounds (BTEX, PAHs and other substituted phenols). Based on the 16S rRNA gene sequences, the isolates were mainly affiliated with the following genera: Achromobacter, Aeromonas, Bacillus, Brevibacillus, Brevibacterium, Brevundimonas, Enterobacter, Escherichia, Kocuria, Macrococcus, Pseudomonas, Rhizobium and Serratia. Kinetic experiments showed that two strains belonging to the genus Kocuria and Macrococcus had the highest rate of phenol degradation. For most strains, growth and biodegradation were inhibited at phenol concentrations above 0.2g.l-1 except for four isolates able to tolerate and grow on phenol or p-cresol up to 1g.l-1. On these four strains, two belonged to the genus Bacillus, one to the genus Comamonas and the last to the genus Lysinibacillus. Strains of Bacillus and Lysinibacillus have shown promising potential for biotechnological applications because of their high tolerance and rapid degradation of alkylphenols. On the other hand, molecular approaches have been used to explore the potential for degradation of wastewater bacteria when incubated in microcosms with phenol, p-cresol or 3,4-dimethylphenol. Monitoring of CO2 released in the gas phase by GC/MS indicated that all three substrates were rapidly mineralized. To analyze changes in microbiological diversity induced by phenol, p-cresol or 3,4-dimethylphenol, metagenomic DNA was extracted from wastewater samples incubated with each of these components. For each phenol hydroxylase family (LmPH and pheA1), sets of primers were used to amplify by PCR genes encoding the large subunit of this enzyme. After cloning and sequencing the obtained gene fragments, sequence analysis revealed that the diversity of hydroxylases observed depended on the alkylphenol provided as a carbon source. The results suggest that bacteria belonging to the group Actinobacteria, Betaproteobacteria and Gammaproteobacteria contribute predominantly to biodegradation. Many PH sequences are not related to those of known bacteria, suggesting that the degradation of (alkyl)phenols in situ has been mainly carried out by non-cultivable bacteria. The results obtained and the tools developed in this study can be used to develop methods for diagnosing and monitoring the biodegradation of pollutants, for example in the context of bioremediation operations for sites polluted by phenols.