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Design and Use of Multiplexed Chemostat Arrays

Design and Use of Multiplexed Chemostat Arrays

Published on: February 23, 2013

Stable competitive coexistence in a continuous fermentor with size-selective properties.

B H Davison¹, K Y San, G Stephanopoulos

¹Dept. of Chemical Engineering, California Institute of Technology Pasadena, CA 91125.

Biotechnology Progress

|June 23, 2010

Summary

A novel reactor design enabled stable coexistence of Escherichia coli (E. coli) and Saccharomyces cerevisiae (yeast) in continuous culture by exploiting size differences for selective cell retention and removal.

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Area of Science:

Biotechnology and Bioprocessing
Microbial Ecology
Chemical Engineering

Background:

Achieving stable coexistence of microbial species with different growth rates in continuous culture is challenging.
Traditional continuous culture systems often lead to the washout of slower-growing species.
Size-based separation offers a potential strategy for managing mixed microbial populations.

Purpose of the Study:

To develop and evaluate a size-selective reactor for enabling stable coexistence of Escherichia coli and Saccharomyces cerevisiae.
To investigate the mechanisms of size-based cell retention and removal in a mixed culture.
To analyze the stability conditions for microbial coexistence in the developed reactor system.

Main Methods:

Construction of a continuous culture reactor with an inclined side-arm for enhanced cell sedimentation and recycling.
Utilizing differential cell size between Saccharomyces cerevisiae (larger) and Escherichia coli (smaller) for separation.
Performing stability analysis based on net removal rates as a function of cell concentration.
Experimental measurement of the net removal rate function using a separate system.

Main Results:

The size-selective reactor successfully maintained a stable mixed culture of E. coli and S. cerevisiae.
Larger yeast cells were preferentially retained and recycled, while smaller, faster-growing bacteria were removed.
Stability was achieved when the net yeast removal rate function was concave up, observed with growth in the settler at low biomass.

Conclusions:

Size-selective reactors can effectively manage mixed microbial cultures with different characteristics.
Enhanced sedimentation in an inclined side-arm facilitates preferential retention of larger cells.
Microbial growth within the settler can contribute to the stability of coexistence steady states in continuous culture.