A Non-Contact Electronic Nose System Based on Off-Gas Response for Real-Time NH₄⁺ Monitoring in Fermentation

Area of Science:

• Biotechnology
• Chemical Engineering
• Sensor Technology

Background:

• Real-time monitoring of ammonium nitrogen (NH4+) concentration is crucial for optimizing biological fermentation processes.
• Traditional offline methods like spectrophotometry suffer from monitoring lag and contamination risks due to contact sampling.

Purpose of the Study:

• To develop an intelligent electronic nose system for non-contact, real-time monitoring of NH4+ concentration in fermentation broth.
• To establish a quantitative relationship between fermentation off-gas signals and NH4+ concentration.
• To provide a novel method for monitoring key fermentation parameters.

Main Methods:

• Development of an electronic nose system utilizing fermentation off-gas signals.
• Implementation of a five-phase gas switching strategy to mitigate sensor drift in metal-oxide-semiconductor (MOS) sensors.
• Application of a light neural network for intelligent prediction of NH4+ concentration.

Main Results:

• The developed system achieved non-contact, real-time monitoring of NH4+ concentration during gentamicin fermentation.
• Experimental results showed high accuracy, with a coefficient of determination (R²) of 0.9871 and a root mean square error (RMSE) of 0.0317 g/L compared to offline measurements.
• The system demonstrated improved prediction speed and accuracy.

Conclusions:

• The electronic nose system offers a viable alternative to traditional offline monitoring methods for fermentation processes.
• This non-contact monitoring technique can be applied to optimize various biological fermentation processes beyond gentamicin production.
• The study highlights the potential of off-gas analysis combined with intelligent systems for industrial bioprocess monitoring.