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Techniques for the Evolution of Robust Pentose-fermenting Yeast for Bioconversion of Lignocellulose to Ethanol
Published on: October 24, 2016
Parameter oscillation attenuation and mechanism exploration for continuous VHG ethanol fermentation.
F W Bai1, X M Ge, W A Anderson
1Department of Bioscience and Bioengineering, Dalian University of Technology, Dalian 116023, China. fwbai@dlut.edu.cn
Biotechnology and Bioengineering
|October 25, 2008
Summary
Continuous ethanol fermentation using Saccharomyces cerevisiae in a very high gravity medium showed oscillations. Packing bioreactors with Intalox ceramic saddles attenuated these oscillations, improving fermentation performance by supporting viable, immobilized yeast cells.
Area of Science:
- Biotechnology
- Biochemical Engineering
- Fermentation Technology
Background:
- Continuous ethanol fermentation in very high gravity media can exhibit oscillations in glucose, ethanol, and biomass.
- These oscillations negatively impact overall fermentation performance.
- Understanding factors that stabilize continuous fermentation is crucial for industrial applications.
Purpose of the Study:
- To investigate methods for attenuating oscillations in a continuous ethanol fermentation system.
- To evaluate the effect of packing materials in tubular bioreactors on fermentation stability.
- To determine the role of yeast cell immobilization and viability in oscillation attenuation.
Main Methods:
- Established a bioreactor system with a stirred tank and three series tubular bioreactors.
- Conducted continuous fermentation using Saccharomyces cerevisiae in a 280 g L(-1) glucose medium.
- Packed tubular bioreactors with various materials (Intalox ceramic saddles, wood chips, porous polyurethane, Raschig rings) to assess immobilization effects.
- Analyzed residence time distribution and yeast cell viability.
Main Results:
- Sustainable oscillations were observed at a dilution rate of 0.027 h(-1).
- Packing with Intalox ceramic saddles and wood chips attenuated oscillations and improved performance.
- Porous polyurethane packing, despite high immobilization, did not attenuate oscillations due to low cell viability.
- Raschig rings without immobilization effect did not alter oscillatory behavior.
Conclusions:
- Yeast cell immobilization with moderate effects, ensuring cell viability, is key to attenuating oscillations in continuous ethanol fermentation.
- Packing materials that support viable, renewable immobilized yeast populations enhance fermentation stability and performance.
- The packing's physical properties (e.g., backmixing reduction) were less critical than biological factors for oscillation attenuation.
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