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Related Experiment Video

Updated: Jul 4, 2026

Techniques for the Evolution of Robust Pentose-fermenting Yeast for Bioconversion of Lignocellulose to Ethanol

Techniques for the Evolution of Robust Pentose-fermenting Yeast for Bioconversion of Lignocellulose to Ethanol

Published on: October 24, 2016

Competitive yeast fermentation with selective flocculation and recycle.

R H Davis¹, C S Parnham

¹Department of Chemical Engineering, University of Colorado, Boulder, Colorado 80309-0424, USA.

Biotechnology and Bioengineering

|February 5, 1989

Summary

This summary is machine-generated.

Selective recycle in continuous fermentation allows slower-growing, flocculent yeast to dominate over faster-growing, nonflocculent strains. This method uses cell sedimentation and recycling to maintain desired microbial populations.

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Area of Science:

Biotechnology
Microbial Ecology
Chemical Engineering

Background:

Continuous fermentations often face challenges with faster-growing strains outcompeting slower ones.
Maintaining specific microbial populations, like those with desirable traits (e.g., flocculation), can be difficult in chemostat systems.

Purpose of the Study:

To investigate a method for maintaining a slower-growing, flocculent Saccharomyces cerevisiae strain in continuous fermentation against a faster-growing, nonflocculent competitor.
To develop and validate a bioreactor-settler system with selective recycle for microbial population control.

Main Methods:

Utilized a chemostat system with two Saccharomyces cerevisiae strains differing in growth rate and flocculation.
Implemented an inclined settler to separate flocculent cells based on sedimentation rate.
Recycled concentrated, flocculent cells from the settler underflow back to the chemostat.

Main Results:

Without recycle, the nonflocculent, faster-growing strain dominated the culture.
With selective recycle, the slower-growing, flocculent yeast was successfully maintained as the dominant species.
Theoretical modeling supported the experimental observations of strain competition in the bioreactor-settler system.

Conclusions:

Selective recycle, exploiting flocculation and sedimentation, is an effective strategy for maintaining slower-growing yeast strains in continuous culture.
This approach offers a viable method for sustaining unstable recombinant microorganisms in continuous fermentation processes.
The bioreactor-settler system provides a robust platform for managing microbial population dynamics.