Improving biodegradation of benzo(Ghi)perylene in soil: Effects of bacterial co-culture, agrowaste and biosurfactant supplementation

Abstract

The feasibility of achieving high biodegradation of benzo(ghi)perylene (BghiP), one of the most recalcitrant and carcinogenic PAHs, was investigated in soil samples. Microorganisms used were Bacillus licheniformis STK 01, Bacillus subtilis STK 02, and Pseudomonas aeruginosa STK 03, with Bacillus licheniformis STK 01 being the primary B(ghi)P biodegrader. The effects of co-culturing the isolates, biosurfactant augmentation, and using phenanthrene (Phe) and Beta vulgaris as co-metabolic substrates were investigated in a 60 day trial experiment. B(ghi)P concentrations were determined by a GC-FID while degradation levels were estimated by mass balance analysis. At the end of the experiment, 52.70%, 40.50%, and 58.36% B(ghi)P were degraded by B. licheniformis STK 01, B. subtilis STK 02, and P. aeruginosa STK 03 respectively, in mono-septic cultures without supplementation. However, the co-culturing of B. licheniformis and B. subtilis improved the degradation of B(ghi)P to 60.76%, B. licheniformis supplementation with Beta vulgaris waste increased the degradation to 58.36%, whereas biosurfactant addition to B. licheniformis increased the degradation to 60.90%. Moreover, B(ghi)P degradation kinetics observed for another 60 days, using B. licheniformis culture with biosurfactant supplementation, showed a further increased to 61.37%. Overall, the biological systems used, achieved a significant degradation efficiency of B(ghi)P in all the cultures studied, while first-order rate kinetics succinctly described the experimental kinetic data (R = 0.9878).