A review on biosurfactant producing bacteria for remediation of petroleum contaminated soils

Abstract

The discharge of potentially toxic petroleum hydrocarbons into the environment has been a matter of concern, as these organic pollutants accumulate in many ecosystems due to their hydrophobicity and low bioavailability. Petroleum hydrocarbons are neurotoxic and carcinogenic organic pollutants, extremely harmful to human and environmental health. Traditional treatment methods for removing hydrocarbons from polluted areas, including various mechanical and chemical strategies, are ineffective and costly. However, many indigenous microorganisms in soil and water can utilise hydrocarbon compounds as sources of carbon and energy and hence, can be employed to degrade hydrocarbon contaminants. Therefore, bioremediation using bacteria that degrade petroleum hydrocarbons is commonly viewed as an environmentally acceptable and effective method. The efficacy of bioremediation can be boosted further by using potential biosurfactant-producing microorganisms, as biosurfactants reduce surface tension, promote emulsification and micelle formation, making hydrocarbons bio-available for microbial breakdown. Further, introducing nanoparticles can improve the solubility of hydrophobic hydrocarbons as well as microbial synthesis of biosurfactants, hence establishing a favourable environment for microbial breakdown of these chemicals. The review provides insights into the role of microbes in the bioremediation of soils contaminated with petroleum hydrocarbons and emphasises the significance of biosurfactants and potential biosurfactant-producing bacteria. The review partly focusses on how nanotechnology is being employed in different critical bioremediation processes.

Keywords: Bioremediation; Biosurfactants; Microorganisms; Nanoparticles; Petroleum hydrocarbons; Soil contamination.

Fig. 1

Basic principle of aerobic hydrocarbon breakdown by microorganisms. Adapted and redrawn from: Das and Chandra (2011). NH4+ Ammonium ion, PO43- Orthophosphate, SO42- Sulfate, Ferric iron; CO2 carbon dioxide, H2O water, O2 Oxygen, TCA Tricarboxylic acid cycle

Fig. 2

Mechanisms of biosurfactant-assisted microbial breakdown of hydrophobic compounds. Adapted and redrawn from: Bami et al. (2022)

Fig. 3

Schematic diagram of biosynthetic pathway for synthesis of biosurfactant. Adapted and redrawn from: Karlapudi et al. (2018)