Role of filamentous fungi to remove petroleum hydrocarbons from the environment

Abstract

Excessive use of petroleum hydrocarbons is causing many problems in the ecosystem. Practically speaking, injudicious use and inappropriate discharge of all forms of hydrocarbons compounds are harmful for the ecosystem. On the other hand, hydrocarbon components like polyaromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) and their biodegradation products are known for their carcinogenic behavior. The reason of persistence of carbon-based compounds (petroleum hydrocarbons) for a long time in the ecosystem depends on many factors such as the physical factors, type of soil, type of microbes in that particular environment, water and sediment of that area, and above all the chemical nature of the petroleum hydrocarbon. The degradation rate of any hydrocarbon product depends upon the chemical nature of the compound, influence of physical factors (here temperature plays a significant role), and accessibility of hydrocarbon as carbon source for microbes, especially the extracellular enzymes secreted by the microbes. The hydrocarbon compounds released in the soil sediments are easy to degrade compared to the aquatic system; since the diversity of microbes in soil and sediment is more, therefore, released hydrocarbon compounds are easily degraded into simple and nontoxic components. Filamentous fungi are a very important biodegrader, owing to their greater biomass compared to bacterial cell. The fungi have more surface area for biosorption and enzyme secretion for efficient biodegradation of petroleum hydrocarbons. In addition to fungi, other organisms such as bacteria and algae have also been employed as an efficient hydrocarbon biodegrader. The main problem with petroleum hydrocarbon biodegradation is that owing to the recalcitrant nature of petrochemicals, the process is complicated, and it also takes a long time for mineralization. Environmental factors also determine the fate of petroleum hydrocarbons in aquatic and terrestrial ecosystem and also rely on several climatic conditions such as temperature, light, aerobic and anaerobic conditions, pH, wind, availability of nitrogen compounds, presence of humic acids, and salinity. There are several methods and approaches used all over the globe to remove or biodegrade the unwanted hydrocarbons using physical and chemical means, but these approaches are not efficient, and moreover they are not cost-effective. The use of biological means by applying potential microbes for bioremediation is an efficient, eco-friendly, and cost-effective tactic without addition of any unwanted load on the environment.