Anaerobic biodegradation ofPara-cresol under three reducing conditions

Area of Science:

• Environmental microbiology
• Biogeochemical cycles

Background:

• p-Cresol is an aromatic organic compound found in various environments.
• Understanding its anaerobic degradation is crucial for environmental remediation.
• Microbial communities play a key role in the breakdown of organic pollutants.

Purpose of the Study:

• To investigate the anaerobic degradation pathways of p-cresol.
• To compare degradation under different redox conditions: denitrifying, sulfidogenic, and methanogenic.
• To identify intermediate metabolites and elucidate the microbial metabolic routes.

Main Methods:

• Incubation of sediment microcosms with p-cresol under controlled anaerobic conditions.
• Monitoring of p-cresol and metabolite concentrations over time.
• Analysis of gaseous end products (N2, CH4, CO2) and sulfate reduction.

Main Results:

• p-Cresol was completely degraded under all tested anaerobic conditions (denitrifying, sulfidogenic, methanogenic).
• Acclimation significantly increased the degradation rate of p-cresol.
• Metabolism proceeded via p-hydroxybenzaldehyde and p-hydroxybenzoate, with benzoate detected only in methanogenic cultures.

Conclusions:

• The initial anaerobic degradation pathway of p-cresol is conserved across different electron-accepting conditions.
• Oxidation of the methyl group to form p-hydroxybenzaldehyde and p-hydroxybenzoate is a common initial step.
• The degradation pathway may diverge after p-hydroxybenzoate formation based on the available electron acceptor.