Biodegradation and phytotoxicity assessment of phenanthrene by biosurfactant-producing Bacillus pumilus 1529 bacteria

ABSTRACT

Phenanthrene is a toxic and mutagenic pollutant that can cause severe environmental and human health issues. The bioremediation of these polyaromatic hydrocarbons (PAHs) is possible with a biosurfactant by enhancing hydrophobicity. In this study, the production of a biosurfactant by Bacillus pumilus 1529 and its effects on the phenanthrene biodegradation pathway were examined. Biosurfactant production was determined using hemolytic activity, emulsification index, and surface tension. For phenanthrene metabolite detection, samples at 0, 7, 14, and 21 incubation days were analysed by gas chromatography-mass (GC-mass) spectrometry. The results showed that Bacillus pumilus 1529 can reduce surface tension to 22.83 ± 1.1 mN m⁻¹. Furthermore, the GC-mass spectrometry analysis showed that 1-hydroxy-2-naphthoic acid, benzaldehyde, o-phthalic acid, and phenylacetic acid were notable phenanthrene metabolites produced during phenanthrene biodegradation. Biodegraded phenanthrene and its metabolites have a less toxic effect on the germination of safflower seeds than non-biodegraded phenanthrene. The IC50 of phenanthrene on seed germination after biodegradation was increased to approximately 113 mg L⁻¹. In general, biodegradation aided by biosurfactant producing bacteria contributed to turning the toxic phenanthrene into less harmful metabolites with lower phytotoxicity effects, indicating that its application in the bioremediation of PAHs is promising.

KEYWORDS:

• Bioassays
• germination
• metabolites
• PAH
• phthalic acid

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes on contributors

Shila Khajavi-Shojaei is a graduated Ph.D. student of soil science (soil chemistry and fertility) at Department of Soil Science, Shahid Chamran University of Ahvaz, Ahvaz, Iran. She achieved her Bachelor's and Master's degrees in soil science from the Shahid Chamran University of Ahvaz, Ahvaz, Iran.

Abdolamir Moezzi is an Associate Professor at Department of Soil Science, Shahid Chamran University of Ahvaz, Ahvaz, Iran.

Naeimeh Enayatizamir is an Associate Professor at Department of Soil Science, Shahid Chamran University of Ahvaz, Ahvaz, Iran.

Babak Mokhtari is an Associate Professor at Department of Chemistry, Shahid Chamran University of Ahvaz, Ahvaz, Iran.

Additional information

Funding

This work was supported by Shahid Chamran University of Ahvaz [grant number 92/04/04/874095].