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.
