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Levan production by Zymomonas mobilis in batch and continuous fermentation systems
Selim Silbir1, Seval Dagbagli, Sirma Yegin
1Ege University, Faculty of Engineering, Department of Food Engineering, 35100 Bornova, İzmir, Turkey.
Carbohydrate Polymers
|November 27, 2013
Summary
Zymomonas mobilis efficiently produces levan, a biopolymer, using sucrose. Optimal conditions in batch fermentation yielded 40.2 g/L levan, while continuous fermentation achieved high productivity.
Area of Science:
- Biotechnology
- Microbial Fermentation
- Biopolymer Production
Background:
- Levan is a microbial exopolysaccharide with diverse industrial applications.
- Zymomonas mobilis is known for its efficient carbohydrate metabolism.
- Optimizing levan production is crucial for its commercial viability.
Purpose of the Study:
- To investigate levan production by Zymomonas mobilis in batch and continuous fermentation systems.
- To determine optimal conditions for maximizing levan yield and productivity.
- To evaluate the impact of different nitrogen sources and fermentation parameters.
Main Methods:
- Batch fermentation using Zymomonas mobilis B-14023 with sucrose and various organic nitrogen sources.
- Response surface methodology to optimize initial substrate concentration, incubation time, and initial pH for batch cultures.
- Continuous fermentation in a packed bed bioreactor with Ca-alginate immobilized cells.
- Analysis of levan concentration and volumetric productivity at different dilution rates.
Main Results:
- Yeast extract was identified as the optimal nitrogen source for levan production.
- Maximum levan concentration of 40.2 g/L was achieved in batch culture at 299.1 g/L initial substrate, 42.3 h incubation, and pH 6.0.
- Continuous fermentation yielded a maximum levan concentration of 31.8 g/L at a dilution rate of 0.14 h(-1).
- Maximum volumetric productivity of 6.556 g/(Lh) was obtained at a dilution rate of 0.22 h(-1) in continuous fermentation.
- Higher dilution rates decreased levan concentration and increased residual sugar.
Conclusions:
- Zymomonas mobilis is a promising microorganism for efficient levan biosynthesis.
- Optimized batch fermentation parameters significantly enhance levan yield.
- Continuous fermentation with immobilized cells offers a viable strategy for high-productivity levan production.
- Further research can explore scale-up and downstream processing for industrial applications.
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