Micro-nano bubbles enhanced biodegradation of n-hexane by a new isolated Pseudomonas sp. ZZH-1

n-Hexane, a recalcitrant volatile organic compound (VOC), poses significant challenges for microbial degradation due to its high volatility and strong hydrophobicity. This study addresses this limitation by isolating a highly efficient degrading bacterium and proposing a novel strategy to enhance n-hexane gas-liquid mass transfer by micro-nano bubbles (MNBs) (generated with compressed air and inorganic salt solution through dissolved air release under 0.4 MPa). The n-hexane degrading bacteria were preliminarily classified as Pseudomonas sp. and named Pseudomonas sp. ZZH-1, utilizing n-hexane as its sole carbon and energy source. ZZH-1 exhibits exceptional environmental adaptability, achieving a maximum cell density (OD₆₀₀) of 0.21 within 21 h and complete degradation (>99 %) of 132 mg·L^-1n-hexane. Critically, MNBs technology was applied and compared with traditional strategies (silicone oil, surfactants) for enhancing n-hexane biodegradation. MNBs emerged as the most effective approach, enabling complete degradation of up to 330 mg·L^-1n-hexane within 38 h and enhancing mineralization efficiency. The kinetic performance was also enhanced with the application of MNBs, yielding a maximum specific growth rate of 0.18 h^-1 and a maximum specific degradation rate of 174.34 h^-1. Furthermore, the effect of MNBs on microbial metabolism was investigated through analyzing soluble microbial products (SMPs), the humification index (HIX), and the biological index (BIX). The results indicated that MNBs can promote the release of SMPs and accelerate aerobic microbial metabolism. The synergistic combination of biodegradation and MNBs demonstrates significant potential for application in biofiltration and bioreactor systems treating high concentrations of n-hexane and other recalcitrant hydrocarbons.