Document Detail

Suppressed acid formation by cofeeding of glucose and citrate in Bacillus cultures: emergence of pyruvate kinase as a potential metabolic engineering site.
MedLine Citation:
PMID:  7654309     Owner:  NLM     Status:  MEDLINE    
Microbial cultures typically produce acids when metabolizing the common carbon source, glucose. Acid production not only represents a waste of carbon, but its accumulation can limit cell concentration and culture stability, thereby reducing productivity. On the basis of prior work, acid production was attributed to be due to a mismatch between glycolytic and tricarboxylic acid (TCA) cycle capacities. To suppress acid production, a strategy entailing adding citrate to glucose minimal medium proved extremely effective. The effect of citrate on in-vivo flux distribution was quantified using a detailed flux-model. When the molar glucose-citrate ratio was varied between 3 and 6, a significant reduction in glycolytic flux and essentially complete suppression of acid formation was found as compared to chemostat cultures grown solely on glucose. Adding other biosynthetic precursors such as glutamine did not invoke the same suppression, thus indicating that citrate's effect is at the regulatory level. We hypothesized that the reduction of glycolytic flux in the presence of citrate results from its transport being coupled with the uptake of divalent metal ions. Citrate transport alters the intracellular balance of metal ions which in turn could trigger a sophisticated series of metabolic events leading to reduction of the activities of the pyruvate kinase and phosphofructokinase (PFK), the regulatory enzymes of glycolysis. On the basis of this scenario and other regulatory information, pyruvate kinase has emerged as a potential metabolic engineering site. It's deactivation in Bacillus subtilis or Escherichia coli strains is expected to yield constructs with a much lower tendency for making acid byproducts.
A Goel; J Lee; M M Domach; M M Ataai
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Biotechnology progress     Volume:  11     ISSN:  8756-7938     ISO Abbreviation:  Biotechnol. Prog.     Publication Date:    1995 Jul-Aug
Date Detail:
Created Date:  1995-10-03     Completed Date:  1995-10-03     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8506292     Medline TA:  Biotechnol Prog     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  380-5     Citation Subset:  B    
Department of Chemical Engineering, University of Pittsburgh, Pennsylvania 15219, USA.
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MeSH Terms
Bacillus / metabolism*
Citrates / metabolism*
Extracellular Space / metabolism
Genetic Engineering
Glucose / metabolism*
Phosphofructokinase-1 / metabolism
Pyruvate Kinase / metabolism*
Reg. No./Substance:
0/Citrates; 50-99-7/Glucose; EC; EC Kinase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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