Influence of biosurfactant-producing strain Bacillus subtilis BS1 on the mycoremediation of soils contaminated with phenanthrene

In the present study, the biocompatibility between a biosurfactant-producing bacterial strain Bacillus subtilis BS1 and arbuscular mycorrhizal fungi Glomus etunicatum was investigated. Inoculation of BS1 could significantly increase the germination rate and hyphal development of G. etunicatum in vitro, although its metabolic biosurfactant, surfactin, displayed inhibitory effect at high concentrations. Exposed to the stress of phenanthrene inhibited the spore germination and hyphal development of G. etunicatum in vitro, but inoculation of BS1 was found to alleviate the stress of phenanthrene and remarkably promote the mycelium growth of germinated spores. The effect of B. subtilis BS1 on the mycoremediation of soils artificially contaminated with different levels of phenanthrene (0, 50 and 250 mg kg−1) was investigated in pot experiments. Mycorrhizal colonization or BS1 inoculation improved the tolerance to stress of phenanthrene and increased the plant biomass. Biosurfactant secreted by BS1 strain considerably enhanced the solubility of phenanthrene, favoring its enrichment in rhizosphere soil and plant roots. The co-inoculation of BS1 and G. etunicatum significantly decreased the residual concentrations of phenanthrene in soil, and resulted in higher soil enzyme activities of catalase and polyphenol oxidase. Therefore, the inoculation of biosurfactant-producing strain to the mycorrhizosphere could be a potential biotechnological approach for the remediation of soil polluted with polycyclic aromatic hydrocarbons.

► Establishing a new mycoremediation method with biosurfactant-producing bacteria BS1.
► Evaluating the biocompatibility between AMF and BS1 under in vitro condition.
► Determining BS1 could alleviate the stress of phenanthrene on AMF in vitro.
► Co-inoculation of AMF and BS1 could improve the phytoremediation of phenanthrene.