Substrate availability in phenanthrene biodegradation: transfer mechanism and influence on metabolism

Area of Science:

• Environmental microbiology
• Bioremediation

Background:

• Polycyclic aromatic hydrocarbons (PAHs) like phenanthrene are environmental pollutants.
• Bacterial biodegradation is a key process for removing PAHs from contaminated environments.

Purpose of the Study:

• To investigate the mechanism of phenanthrene transfer to bacteria during biodegradation.
• To determine if substrate transfer limits the rate of phenanthrene degradation by Pseudomonas.

Main Methods:

• Utilized a respirometric technique (Sapromat equipment) for quasi-continuous oxygen consumption monitoring.
• Studied phenanthrene biodegradation using crystalline solid and solutions in silicone oil and heptamethylnonane.
• Conducted abiotic experiments to quantify phenanthrene transfer rates to the aqueous phase.

Main Results:

• Bacterial growth rate was consistent across different phenanthrene supply methods.
• Biodegradation rates were limited by the rate of phenanthrene transfer to the aqueous phase.
• A model based on phase-transfer laws accurately predicted biodegradation rates.
• The silicone oil system showed high transfer and biodegradation rates, leading to more metabolite production and less mineralization.

Conclusions:

• Phenanthrene biodegradation is fundamentally dependent on its prior transfer into the aqueous phase.
• The rate of substrate transfer dictates the overall biodegradation kinetics.
• Understanding transfer mechanisms is crucial for optimizing bioremediation strategies for hydrophobic compounds.