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Lactic acid fermentation in a recycle batch reactor using immobilized Lactobacillus casei.
A Senthuran1, V Senthuran, B Mattiasson
1Department of Biotechnology, Center for Chemistry and Chemical Engineering, Lund University, PO Box 124, S-221 00 Lund, Sweden.
Biotechnology and Bioengineering
|July 19, 2008
Summary
Immobilized Lactobacillus casei cells efficiently produced lactic acid in a recycle batch fermentation system. Optimizing yeast extract reduced free cells, increasing fermentation cycles and maintaining high productivity.
Area of Science:
- Biotechnology
- Industrial Microbiology
Background:
- Lactic acid is a valuable chemical produced via fermentation.
- Immobilization of microbial cells can enhance fermentation efficiency and productivity.
- Lactobacillus casei subsp. rhamnosus is a key microorganism for lactic acid production.
Purpose of the Study:
- To investigate lactic acid production using immobilized Lactobacillus casei subsp. rhamnosus in a recycle batch fermentation.
- To optimize fermentation conditions for enhanced productivity and yield.
- To evaluate the impact of cell immobilization and medium composition on fermentation performance.
Main Methods:
- Immobilization of Lactobacillus casei subsp. rhamnosus on polyethyleneimine-coated foam glass particles (Pora-bact A).
- Recycle batch fermentation in a system combining a packed column and a stirred tank reactor for pH control.
- Optimization of culture medium composition, including whey, yeast extract, and Mn(2+) ions.
- Investigation of substrate concentration and medium volume effects on fermentation kinetics.
Main Results:
- Achieved average reactor productivity of 4.3–4.6 g/L·h with complete substrate utilization and >90% product yield.
- Maintained sugar consumption and lactate yield with increased medium volume up to 10 times the biocatalyst volume.
- Reducing yeast extract concentration decreased suspended biomass, increasing fermentation cycles and maintaining productivity.
- Ion-exchange adsorption was used for lactic acid recovery from the clarified broth.
Conclusions:
- Recycle batch fermentation with immobilized Lactobacillus casei subsp. rhamnosus is a viable method for efficient lactic acid production.
- Optimizing yeast extract concentration is crucial for maximizing fermentation cycles by minimizing suspended biomass.
- The developed system demonstrates high productivity and yield, with potential for industrial application.
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