Increased Mevalonate Production Using Engineered Citrate Synthase and Phosphofructokinase Variants of Escherichia coli.

Mevalonate is a biochemical precursor to a wide range of isoprenoids. The mevalonate pathway uses three moles of acetyl-CoA, and therefore native pathways which metabolize acetyl-CoA compete with mevalonate synthesis. Moreover, the final step in mevalonate formation, mediated by hydroxymethylglutaryl-CoA reductase, requires NADPH as a co-substrate.

Production of Esters in Using Citrate Synthase Variants.

Acetate esters comprise a wide range of products including fragrances and industrial solvents. Biosynthesis of esters offers a promising alternative to chemical synthesis because such routes use renewable carbohydrate resources and minimize the generation of waste. One biochemical method for ester formation relies on the gene from , which encodes alcohol-O-acyltransferase (AAT) which converts acetyl-CoA and an exogenously supplied alcohol into the ester.

Citrate synthase variants improve yield of acetyl-CoA derived 3-hydroxybutyrate in Escherichia coli.

Background: The microbial chiral product (R)-3-hydroxybutyrate (3-HB) is a gateway to several industrial and medical compounds. Acetyl-CoA is the key precursor for 3-HB, and several native pathways compete with 3-HB production. The principal competing pathway in wild-type Escherichia coli for acetyl-CoA is mediated by citrate synthase (coded by gltA), which directs over 60% of the acetyl-CoA into the tricarboxylic acid cycle.

variants coding pyruvate dehydrogenase improve the generation of pyruvate-derived acetoin.

Several chromosomally expressed AceE variants were constructed in and compared using glucose as the sole carbon source. These variants were examined in shake flask cultures for growth rate, pyruvate accumulation, and acetoin production via heterologous expression of the and genes from . The best acetoin-producing strains were subsequently studied in controlled batch culture at the one-liter scale.

Nutrient-Limited Operational Strategies for the Microbial Production of Biochemicals.

Limiting an essential nutrient has a profound impact on microbial growth. The notion of growth under limited conditions was first described using simple Monod kinetics proposed in the 1940s. Different operational modes (chemostat, fed-batch processes) were soon developed to address questions related to microbial physiology and cell maintenance and to enhance product formation.