ISSN:
1476-5535
Keywords:
Acetate
;
ppc
;
Pyruvate
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
Summary Isogenic strains ofEscherichia coli were grown aerobically in minimal medium in a 2-liter airlift fermentor to determine whether appc (phosphoenolpyruvate carboxylase) mutation had the effect of directing glucose carbon into phenylalanine synthesis. Two host strains, YMC9 (ppc +) and KB285 (ppc −) were used, either with (Phec) or without (Phe0) a plasmid which determines constitutive phenylalanine production. Carbon consumption and metabolic products were monitored. Phenylalanine production occurred only in strains carrying the Phec plasmid.ppc − strains produced less cell mass and more acetate, pyruvate, and phenylalanine (in the Phec strains) than did isogenicppc + strains. Lactate and ethanol production were not detected in any of the strains. Phec strains produced less acetate and pyruvate than their Phe0 homologs. Importantly,ppc −/Phec produced at least six times as much phenylalanine (0.32 g phenylalanine/g dry weight cells) asppc +/Phec. Even in this case, however, phenylalanine was produced at ten-fold lower levels than acetate. Thus, although theppc − mutation stimulates phenylalanine production, it also stimulates the production of unwanted by-products such as acetate and pyruvate.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01569421
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