Previous Article | Next Article ![]()
Appl. Environ. Microbiol., 10 1996, 3687-3696, Vol 62, No. 10
U Sauer, V Hatzimanikatis, HP Hohmann, M Manneberg, AP van Loon and JE Bailey
Continuous cultivation in a glucose-limited chemostat was used to determine
the growth parameters of wild-type Bacillus subtilis and of a recombinant,
riboflavin-producing strain. Maintenance coefficients of 0.45 and 0.66 mmol
of glucose g-1 h-1 were determined for the wild-type and recombinant
strains, respectively. However, the maximum molar growth yield of 82 to 85
g (cell dry weight)/mol of glucose was found to be almost identical in both
strains. A nonlinear relationship between the specific riboflavin
production rate and the dilution rate was observed, revealing a coupling of
product formation and growth under strict substrate-limited conditions.
Most prominently, riboflavin formation completely ceased at specific growth
rates below 0.15 h-1. For molecular characterization of B. subtilis, the
total amino acid composition of the wild type was experimentally determined
and the complete building block requirements for biomass formation were
derived. In particular, the murein sacculus was found to constitute
approximately 9% of B. subtilis biomass, three- to fivefold more than in
Escherichia coli. Estimation of intracellular metabolic fluxes by a refined
mass balance approach revealed a substantial, growth rate- dependent flux
through the oxidative branch of the pentose phosphate pathway. Furthermore,
this flux is indicated to be increased in the strain engineered for
riboflavin formation. Glucose catabolism at low growth rates with reduced
biomass yields was supported mainly by the tricarboxylic acid cycle.
Copyright © 1996, American Society for Microbiology
Physiology and metabolic fluxes of wild-type and riboflavin-producing Bacillus subtilis
Institute of Biotechnology, Eidgenossische Technische Hochschule Zurich, Switzerland.
This article has been cited by other articles:
| J. Bacteriol. | Microbiol. Mol. Biol. Rev. | Eukaryot. Cell | All ASM Journals |
|---|