On-line monitoring of CO2 production in Lactococcus lactis during physiological pH decrease using membrane inlet mass...

Area of Science:

• Biotechnology
• Analytical Chemistry
• Microbiology

Background:

• Monitoring dissolved carbon dioxide (CO2) production is challenging due to its chemical behavior and pH-dependent volatility.
• Existing methods struggle with systems experiencing rapid pH fluctuations, limiting quantitative analysis.

Purpose of the Study:

• To develop and validate a method for direct, continuous, and quantitative monitoring of dissolved CO2 concentration and production rates.
• To overcome limitations posed by rapid pH changes (approx. 2 units in 15 min) in monitoring CO2.

Main Methods:

• Utilized membrane inlet mass spectrometry (MIMS) for CO2 measurement.
• Integrated on-line pH analysis to correct MIMS data for pH dependency.
• Developed an experimentally established calibration model valid for pH ranges of 3.5 to 7.

Main Results:

• The method accurately quantifies CO2 production during Lactococcus lactis fermentations with pH drops up to 3 units.
• Achieved an accuracy of approximately 5% in CO2 production measurements.
• Demonstrated that increasing initial extracellular pH from 6 to 6.8 significantly increases CO2 production rate during anaerobic glucose fermentation.

Conclusions:

• The presented method enables reliable, real-time monitoring of CO2 production in dynamic pH environments.
• This advancement is critical for studying microbial metabolism and fermentation processes.
• The findings highlight the significant impact of initial pH on CO2 generation in Lactococcus lactis.