Sodium lauryl ether sulfate (SLES) degradation by nitrate-reducing bacteria

Area of Science:

• Environmental microbiology
• Wastewater treatment
• Biodegradation

Background:

• Sodium lauryl ether sulfate (SLES) is a common detergent ingredient found in wastewater.
• Aerobic degradation of SLES is understood, but its fate in anoxic environments is largely unknown.
• Denitrification tanks in wastewater treatment plants (WWTPs) represent a key anoxic environment.

Purpose of the Study:

• To investigate the anoxic biodegradation of SLES in wastewater.
• To isolate and identify nitrate-reducing bacteria capable of SLES degradation under anoxic conditions.
• To characterize the SLES degradation capabilities and tolerance of isolated bacterial strains.

Main Methods:

• Enrichment and isolation of nitrate-reducing bacteria using SLES as the sole carbon source at varying concentrations (50-1000 mg L⁻¹).
• Isolation of specific bacterial strains: Aeromonas hydrophila S7, Pseudomonas stutzeri S8, and Pseudomonas nitroreducens S11.
• Assessing SLES degradation rates and bacterial tolerance to high SLES concentrations (up to 40 g L⁻¹).

Main Results:

• Pseudomonas strains S8 and S11 demonstrated rapid SLES degradation (500 mg L⁻¹ in <1 day) under denitrifying conditions.
• Strains S8 and S11 exhibited high tolerance to SLES, growing at concentrations up to 40 g L⁻¹.
• Pseudomonas nitroreducens S11 was the most effective anoxic SLES degrader, breaking down 41% of 500 mg L⁻¹ SLES, likely using both ester and ether cleavage pathways.

Conclusions:

• Specific Pseudomonas strains can effectively degrade SLES in anoxic environments, contributing to its removal in WWTPs.
• The high SLES tolerance of strains S8 and S11 suggests their potential for application in specialized bioremediation strategies.
• Anoxic SLES degradation by P. nitroreducens S11 differs from aerobic pathways, involving distinct cleavage mechanisms.