Semi-continuous detection of toxic hexavalent chromium using a sulfur-oxidizing bacteria biosensor

Area of Science:

• Environmental Science
• Microbiology
• Analytical Chemistry

Background:

• Toxicity testing is crucial for environmental risk assessment.
• Sulfur-oxidizing bacteria (SOB) possess metabolic properties exploitable for biosensing applications.
• Monitoring water quality requires sensitive and rapid detection methods for toxic chemicals.

Purpose of the Study:

• To develop and evaluate a biosensor for detecting toxic chemicals in water.
• To utilize the metabolic activity of SOB for detecting hexavalent chromium (Cr(6+)).
• To establish a rapid, early warning system for environmental protection.

Main Methods:

• A biosensor was engineered utilizing the aerobic oxidation of elemental sulfur by SOB.
• The oxidation process, producing sulfuric acid, was monitored via changes in electrical conductivity (EC) and pH.
• The biosensor was operated in a semi-continuous mode, involving rapid feeding and batch reaction cycles.
• Hexavalent chromium (Cr(6+)) was introduced to assess the biosensor's response to toxicity.

Main Results:

• Exposure to Cr(6+) resulted in decreased effluent EC and increased pH (from 2-3 to 6) within five hours.
• These observed changes in EC and pH are indicative of Cr(6+) toxicity impacting SOB metabolic activity.
• The SOB biosensor demonstrated sensitivity to toxic levels of Cr(6+).

Conclusions:

• The SOB biosensor offers a simple and effective method for detecting toxic Cr(6+) in water.
• The detection time scale, ranging from minutes to hours, is suitable for early warning systems.
• This biosensor technology contributes to environmental risk assessment and protection strategies.