Microbial exopolymeric substances and biosurfactants as 'bioavailability enhancers' for polycyclic aromatic hydrocarbons biodegradation

Bacterial cells dwelling in the Polycyclic Aromatic Hydrocarbons (PAH) contaminated ecosystem occur as an eco-community or biofilms having biosurfactants and exopolymeric substances (EPS) producing capacity. Bacteria have developed several mechanisms to utilize the low accessible PAH compounds by modifying their structural and physiological process. EPS provides an adsorption site for PAH binding and acts as an emulsifier, enhancing PAH uptake in bacterial cells. Biosurfactants aid in the solubilization of the low-bioavailable carbon sources by reducing the interfacial surface tension between the aqueous phase and PAH-sorbent matrix, solubilizing PAHs thus making them bioavailable. Mining of exopolysaccharides synthesizing key genes (priming Glycosyltransferase) and biosurfactant producing genes (synthetases) in PAH degrading bacteriomes established their concomitant involvement in PAH solubilization and uptake. The transcriptional and translational regulators (secondary messenger cyclic-di-GMP, quorum sensing molecules, small ribosomal RNAs, two-component signaling molecules) control the synthesis of these 'bioavailability enhancers' towards PAH utilization and have been elucidated explicitly in the current review.