Bacterial community response to modified-biochar and exogenous fungi inoculation during degradation of oil-contaminated clayey sediment in slurry phase

Abstract

Abstract Bioremediation strategies for oil-contaminated clayey sediment are still a major environmental concern due to their reluctance to conventional treatment techniques. The main objective of this study was to evaluate the sequential application of modified biochar and exogenous fungus in slurry phase degradation of crude oil-contaminated clayey sediment. Biochar modification using acid and rhamnolipid increased its surface area from 2.544 to 25.378 m2g-1, followed by a corresponding increase in the hydrogen-carbon and oxygen-carbon ratio, indicating improved stability, polarity, and oxygen contents. The maximum TPH removal efficiency of 82.4% was achieved in treatments with the acid-rhamnolipid-treated biochar, followed by a corresponding increase in FDA hydrolysis activity. Furthermore, high-throughput 16S RNA gene sequencing was employed to identify changes in the bacterial community structures of the original sediment and treatments before and after fungal inoculation. This highlighted Proteobacteria as the dominant phylum, followed by Campilobacterota, Bacteroidota, Actinobacteriota, and Desulfobacterota. In addition, it was observed that fungal inoculation promoted the proliferation of some specific TPH-degraders. Specifically, ASVs associated with Hyphomonas adhaerens and Marinobacter mobilis accounted for 77% and 5% of the total degrading populations in treatments where TPH removal was highest. Findings in this study provide valuable insights into the effect of biochar in the treatment of crude oil-contaminated marine sediments, and a better understanding of the fundamental role of exogenous fungus in the proliferation of efficient TPH-degraders towards effective degradation.