Application of a pH feedback-controlled substrate feeding method in lactic acid production

Area of Science:

• Biotechnology
• Industrial Microbiology
• Fermentation Technology

Background:

• Traditional feeding methods in fed-batch lactic acid fermentation often fail to precisely control substrate concentration.
• This limitation hinders optimal lactic acid production and yield.

Purpose of the Study:

• To develop and evaluate a simple feedback feeding method for synchronous control of pH and substrate concentration.
• To enhance lactic acid production in fed-batch cultures using Lactobacillus lactis-11.

Main Methods:

• A feedback feeding strategy based on pH adjustment was implemented.
• Alkali and substrate were proportionally mixed in the feeding broth, leveraging the linear relationship between alkali consumption and substrate utilization.
• This allowed for automatic substrate concentration control via pH monitoring.

Main Results:

• The developed method maintained residual glucose concentration between 4.1 and 4.9 g L⁻¹.
• Achieved a highest lactic acid concentration of 96.3 g L⁻¹, maximum cell dry weight of 4.7 g L⁻¹, and volumetric productivity of 1.9 g L⁻¹ h⁻¹.
• The yield reached 0.99 g lactic acid per gram of glucose, significantly outperforming batch culture results.

Conclusions:

• The proposed pH-based feedback feeding method is simple, easily operated, and effective for controlling substrate concentration.
• This method offers a feasible and efficient approach for industrial lactic acid production.