Microbial degradation for bioremediation

The Ala Wai Canal was built as a conduit for runoff from major watersheds and functions as a drainage canal and a sediment basin. Due to sediment accumulation, periodic maintenance dredging is required. Contaminants such as polycyclic aromatic hydrocarbons (PAHs), heavy metals, and pesticides, as well as microbial pathogens, may be present in the sediment. Microbes utilize organic compounds for energy and/or growth, either producing new organic compounds as side products or carbon dioxide and water. The objective of this study was to determine if indigenous microbes could utilize potentially carcinogenic PAHs, specifically phenanthrene, as a carbon source. In previous studies, microbes present in the dredged sediment were isolated and identified. Since these microbes have been thriving in contaminated sediment for years, we hypothesize that these microbes may have potential for bioremediation. To determine the phenanthrene degradation capabilities of the four selected indigenous microbes, each strain was inoculated into three different media: 25ppm phenanthrene in basal Bushnell-Haas medium, basal Bushnell-Haas medium (negative control), and Marine Broth (positive control). The growth of these microbes was monitored through a series of turbidity tests and cell counts using a hemocytometer. The degradation activity of phenanthrene was studied using gas chromatography and calorimetry. The results of this study showed that the four microbial strains are able to grow in the presence of phenanthrene and cause a decrease of phenanthrene. Therefore, these microbes are promising candidates for bioremediation of the contaminated sediments.