Composite of PAH-degrading endophytic bacteria reduces contamination and health risks caused by PAHs in vegetables.

Vegetables accumulate polycyclic aromatic hydrocarbons (PAHs) at high concentrations when grown in contaminated sites. Inoculation with PAH-degrading endophytic bacteria (EB) has been recognized as one of the most promising ways to remove PAHs from plant bodies; however, the performance of single endophytic bacteria is generally limited. This investigation used a composite of eight EB to reduce the contamination and health risk posed by 16 EPA priority PAHs in vegetables including Chinese cabbage (Brassica chinensis L.) and pakchoi (Brassica campestris L.). Composite EB have strong PAH degradation abilities, and more than 65% of ∑PAH were degraded after 10-day insuspension with composite EB. Vegetable were contacted with composite EB by seed soaking (SS) and leaf painting (LP) with an EB cell incubation at OD=0.2-1.5. Compared with those in non-inoculated controls, the ∑PAH concentrations in edible parts of Chinese cabbage and pakchoi colonized by composite EB via SS and LP with bacterial suspension at OD=0.2-1.5 were 42.07-70.77% and 15.79-53.20% lower, and the incremental lifetime cancer risk (ILCR) values for males and females were 31.78-84.08% and 26.60-83.40% smaller, respectively. SS was the optimal inoculation method for reducing PAH concentrations and ILCR values. Our results indicate that inoculating plants with composite EB can lower the health risk posed by vegetables contaminated with PAHs, and may be used to mitigate plant PAH contamination.