Development of a Novel PCB-Degrading Biofilm Enriched Biochar Encapsulated with Sol–Gel: A Protective Layer to Sustain Biodegradation Activity

<i>Paraburkholderia xenovorans</i> LB400 biofilms hold the potential to degrade PCBs in contaminated sediment. Nevertheless, unfavorable environmental conditions (e.g., salinity, temperature, and shear force) can interfere with biofilm stability and affect biodegradation potential. Sol-gel encapsulation has been used to protect planktonic cell function due to high material stability and absence of cell washout but has not been employed for biofilm protection. Our study is the first to develop sol-gel application on biofilm-enriched black carbons and evaluate efficacy for prolonging biodegradation potential. We systematically tuned multiple sol-gel recipes to coat biofilms and measured the impact of the sol-gel coating on cell survival and pollutant degradation. The developed sol-gel completely encapsulated biofilm-enriched black carbons and produced both high porosity and appropriate pore size that allowed pollutant transfer from the surrounding environment to the biofilms. The sol-gel maintained physical integrity under saline conditions (simulating marine and estuary sediments) and continuously applied shear force. Additionally, the encapsulated biofilms degraded benzoate, a proof-of-concept organic molecule, and extended biofilm attachment and cell viability for over three months without a carbon and energy source. Our study demonstrates that sol-gel helps sustain PCB-degrading biofilms under environmentally relevant conditions. This novel sol-gel application can potentially improve the bioaugmentation effectiveness and enhance degradation of environmental pollutants.