Biochar-Immobilized Bacterial Consortium Pdc for Enhanced Polycyclic Aromatic Hydrocarbons Degradation: A Study on Optimization and Microbial Analysis

Abstract

This study examines the biodegradation of PAHs (Phenanthrene (PHE), fluoranthene (FLT), and pyrene (PYR)) in a Sequential Batch Reactor (SBR) utilizing sludge obtained from a coking plant. By incrementally increasing pollutant concentrations, we observed a corresponding rise in degradation rates, indicating the presence of PAHs-resistant bacteria. The sludge was subsequently extracted, and the bacterial consortium PDC was domesticated based on a synergistic mechanism involving intermediate metabolites. Optimal degradation conditions were determined to be 30°C, 150 rpm, and a 5% PDC, with PAH concentrations of 100 mg/L for PHE, FLT, and PYR. We embedded the efficient PAH-degrading consortium PDC in biochar-sodium alginate (SA) composite beads to create immobilized microspheres (IMS). The optimal preparation conditions for IMS were identified as follows: 1.25% SA, 0.6% biochar, 7% PDC, a solution of 6% CaCl2, and a crosslinking time of 12 hours. The biochar immobilization technique promoted an increased abundance of Achromobacter and Ochrobactrum within the PDC flora. Additionally, PICRUSt2 predicted an enhanced relative abundance of enzymes associated with PAH degradation in IMS - particularly those involved in the breakdown of PHE, FLT, and PYR (e.g.: naphthalene-1,2-dioxygenase ferredoxin component; alcohol dehydrogenase; salicylate hydroxylase; among others. This study provides valuable insights into the potential application of biochar immobilization technology for bioremediation efforts targeting PAH-contaminated environments.

Keywords: biochar, Immobilized Microspheres, Polycyclic Aromatic Hydrocarbons, Biodegradation, Microbial analysis