In vitro removal of polycyclic aromatic hydrocarbons by lactic acid bacteria

Area of Science:

• Environmental Microbiology
• Food Science
• Toxicology

Background:

• Polycyclic Aromatic Hydrocarbons (PAHs) are persistent organic pollutants found in various food matrices.
• Lactic Acid Bacteria (LABs) are known for their probiotic properties and potential in bioremediation.
• Investigating LABs' ability to remove PAHs is crucial for food safety and human health.

Purpose of the Study:

• To evaluate the efficacy of different LAB strains in removing four specific PAHs (BaP, BaA, Chr, BbF) from aqueous solutions.
• To determine the influence of PAH concentration, bacterial population, and pH on the removal efficiency.
• To assess the role of bacterial cell viability in the PAH binding process.

Main Methods:

• Selected LAB strains were incubated with phosphate buffer saline (PBS) contaminated with varying concentrations of four PAHs.
• The impact of initial PAH concentrations (5-20 μg/ml), bacterial populations (10^7-10^10 CFU/ml), and pH (3, 5, 7) on PAH removal was investigated.
• Bacterial cells were subjected to different treatments (acid, heat, ultrasonic) to assess the necessity of viability for binding.

Main Results:

• All tested LAB strains demonstrated the ability to remove BaA, Chr, BbF, and BaP, with removal order generally BaP > Chr > BaA > BbF.
• Lactobacillus acidophilus LA-5 exhibited the highest PAH binding ability, while Bifidobacterium lactis BB-12 showed the lowest.
• Bacterial cell viability was not essential for PAH binding; inactivated cells (acid-treated, heat-treated, ultrasonic-treated) displayed enhanced binding capabilities, forming irreversible complexes.

Conclusions:

• PAH removal by LABs is significantly influenced by media pH, bacterial strain, and PAH type and concentration.
• Both live and inactivated LAB strains can effectively remove PAHs from aqueous environments, presenting novel strategies for reducing food contamination.
• Findings support future research into the use of probiotic supplements, including dead strains, for mitigating PAHs in humans.