Effect of biofilm parameters and extracellular polymeric substance composition on polycyclic aromatic hydrocarbon degradation

Abstract

Marine bacterial biofilms were studied under different physicochemical conditions for enhanced bioremediation of polycyclic aromatic hydrocarbons (PAHs). Molecular characterization of ten environmental isolates was done by 16S rRNA gene sequencing. The effect of different physicochemical parameters, such as pH, salt concentration, temperature, carbon source on their biofilm production capability was monitored. Various topological parameters of the biofilms such as total biomass (EPS and cells content), thickness, roughness coefficient, diffusion distance and surface to biovolume ratio were studied using a confocal scanning laser microscope (CSLM). Among the various strains studied, the total biomass was maximum for P. aeruginosa N6P6 (106.64 μm³ μm⁻²) followed by S. acidaminiphila NCW702 (26.92 μm³ μm⁻²) indicating the formation of dense biofilm. Significant negative correlation (P < 0.05) was observed between the roughness coefficient of the biofilm and PAH degradation, whereas a significant positive correlation (P < 0.05) was observed between PAH (phenanthrene and pyrene) degradation and total biomass, thickness and diffusion distance of the biofilms. PAH degradation was studied both in planktonic and biofilm modes of growth. Biofilm facilitated degradation of the two PAHs was higher than the planktonic cells. This work demonstrates that the attached phenotypes of the marine bacteria showed noticeable variation in biofilm architecture and, in turn, biodegradation of PAHs.