Proline excretion by Escherichia coli K12
D E Rancourt1, J T Stephenson, G A Vickell
1Guelph-Waterloo Centre for Graduate Work in Chemistry, University of Guelph, Guelph, Ontario, Canada, N1G 2W1.
Biotechnology and Bioengineering
|January 1, 1984
Summary
Proline overproducing E. coli strains only excrete proline when uptake or breakdown is impaired. Genetic defects blocking active transport enhance metabolite excretion for chemical production.
Area of Science:
- Microbiology
- Metabolic Engineering
- Biotechnology
Background:
- Proline overproduction in E. coli K12 was investigated as a model for chemical production.
- Uncontrolled synthesis alone does not lead to proline excretion.
Purpose of the Study:
- To determine the conditions necessary for proline excretion from overproducing E. coli strains.
- To explore the use of genetic lesions to enhance metabolite excretion.
Main Methods:
- Isolation of proline overproducing E. coli mutants.
- Introduction of mutations affecting L-proline transport and catabolism.
- Dansyl derivatization and chromatographic analysis of culture supernatants.
- Batch culture experiments in amino acid production medium.
Main Results:
- Proline excretion occurs only when active uptake and/or catabolism of L-proline are impaired in overproducing strains.
- Proline is the sole amino acid excreted.
- Excreting strains produced 1 g/L proline, while non-excreting overproducing strains produced none.
Conclusions:
- Genetic lesions that eliminate active uptake can specifically enhance metabolite excretion.
- Impaired transport or catabolism is crucial for achieving significant proline excretion in engineered E. coli.
