رسائل ماجيستير
English
2022
Isolation And Characterization Of Active Bacteria Degrading Coronene, An Overly Complex Polycyclic Aromatic Hydrocarbon
Alexis Nzila , أجيبولا حكيم اوكيودي
كلية الكيميائيات والمواد-جامعة الملك فهد للبترول والمعادن · السعودية
Petroleum pollutants have been a major concern in recent years. Among the most important petroleum pollutants are polycyclic aromatic hydrocarbons (PAH). Generally, PAHs are cyclic aromatic hydrocarbons with fused benzene rings ranging from 2 rings and above. Coronene, one of the most complex PAHs is the least studied probably due to its high recalcitrance. In this study, we focus on isolating bacteria that can actively degrade coronene using bioremediation. A bacterial strain, capable of degrading coronene as the only source of carbon was isolated by enrichment of soil-contained inoculum, in a mineral culture medium, in the presence of coronene as the only source of carbon, and salinity at 10% NaCl. This enrichment led to the isolation of the 10SCRN4D strain, and 16S RNA gene sequencing and homology analyses have indicated that this strain belongs to the Halomonas caseinilytica species. The growth rate of this bacterial strain in the presence of coronene was carried out at varying temperatures (30oC, 37 oC and 50 oC), concentrations (5ppm, 25ppm and 50ppm) and pH (3.0, 7.0 and 10.0), salinity (0.5, 10, 20% w/v of NaCl), and the data presented as doubling time (dt). The results indicate pH 7, 30oC and 0.5 % NaCl is the optimum growth condition, characterized by the lowest dt (thus highest growth) of 8.78 hrs. As expected, an increase in coronene concentration led to an increase in doubling time (decrease in growth), from 11.13hrs at 10ppm to 15.71 hrs at 50 ppm. The effect of time variation on the bacterial degradation of coronene was also investigated for a period of 80 days. More than 45% of coronene was degraded on day 40 while 75% of coronene was degraded on day 80, which attests to the fact that the degradation rate increases with the increased duration of the experiment. Thus, the 10SCRN4D strain is a unique halotolerant halophilic bacterium that can grow and degrade in the presence of 7-ring PAH coronene with up to 75% degradation as demonstrated by our study