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J Bacteriol. 1972 November; 112(2): 856-860
Copyright © 1972 American Society for Microbiology. All Rights Reserved.

High-Level Production of ß-Galactosidase by Escherichia coli Merodiploids

Department of Biological Chemistry, UCLA School of Medicine, University of California, Los Angeles, California 90024

ABSTRACT

Two merodiploids of Escherichia coli that contain genes for the lac operon on both chromosome and episome were tested for production of lac enzymes after growth on various carbon sources. The specific activity of ß-galactosidase (and of thiogalactoside transacetylase) was about twice that from haploid cells when grown on glycerol. With succinate as carbon source, the specific activity increased by an additional factor of 3. Up to 25% of the soluble cell protein is ß-galactosidase in these strains, one of which is inducible and the other constitutive. The enzyme is purified easily in high yield by ammonium sulfate fractionation and electrophoresis.

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