Degradation of Crude Oil by Microbial Populations of Lagos Lagoon Water Microcosms ^†

Petroleum hydrocarbon pollution (PHP) poses a significant environmental threat and affects both marine and terrestrial ecosystems. This study focused on the isolation and screening of indigenous petroleum-degrading microorganisms from Mile 2 Lagoon, Lagos, Nigeria. This study aimed to investigate the biodegradability of crude oil and analyse the petroleum–hydrocarbon degradation characteristics of microbial consortia on a laboratory scale. Physicochemical analysis of the lagoon water revealed a neutral pH and high nitrate and phosphate concentrations, indicating minimal prior oil pollution. A continuous enrichment method was employed to cultivate microorganisms, using Ecravos light crude oil as the sole carbon and energy source. The enumeration of total heterotrophic microorganisms and hydrocarbon-utilising microorganisms, along with microbial characterisation, was conducted. This study identified three hydrocarbon-utilising bacteria (THUB-1-3) and two fungal strains (THUF-1-2) and demonstrated their ability to degrade crude oil. The growth profile of these isolates showed exponential growth, with the bacterial consortium achieving a maximum concentration of 9.9 × 10⁶ cfu/ml on day 28. Petroleum degradation kinetics showed that the microbial consortium degraded 93% of the crude oil over 42 days, with variations observed in different hydrocarbon fractions. This study provides valuable insights into the potential of indigenous microbial strains to mitigate the ecological impact of oil spills on aquatic environments.