Nanobubbles promote microbial degradation of polycyclic aromatic hydrocarbons: Enhanced detoxification & optimized degradation pathway

Polycyclic aromatic hydrocarbons (PAHs) are a prevalent type of recalcitrant pollutant that poses significant risks to both the environment and human health. The inherent bio-toxicity of PAHs frequently impedes microbial remediation. This study investigated the capacity of nanobubbles to overcome toxicity limitations and enhance the biodegradation of PAHs through experiments conducted in both solution-phase and soil-phase systems. In liquid systems, the addition of nanobubbles increased the degradation rates of five typical PAHs (pyrene, anthracene, phenanthrene, fluoranthene and benzo[a]pyrene) by 32.3 %-111.5 % compared to control groups during 14 days. Multiple effects of nanobubbles on microbial detoxification were identified, including the bacterial characterization, extracellular polymeric substance (EPS) secretion, and antioxidant production during degradation. It revealed the multifaceted detoxification mechanisms of nanobubbles against PAH toxicity. By preserving cellular integrity, modulating transmembrane transport, and stimulating the secretion of detoxifying substances, nanobubbles effectively regulated metabolic processes in degrading microorganisms. In soil systems, nanobubbles achieved 81 % pyrene degradation within 28 days, representing a 108 % increase over systems without nanobubbles, with bacterial abundance doubling. These results demonstrate the universal enhancement efficacy of nanobubbles across various environmental matrices. Soil metagenomic analysis indicated an increase in functional genes associated with PAHs degradation, particularly those linked to the least-step degradation pathway, suggesting optimization of microbial metabolic processes. The nanobubbles significantly accelerated PAHs degradation while maintaining cell viability, presenting an eco-friendly and cost-effective bioaugmentation strategy for soil remediation.