http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Tryptophan biosynthesis by genetically engineered Escherichia coli utilizing different carbon sources
(Pck), and phosphoenolpyruvate synthase (Pps) in a suitable
(TktA) activity on aromatics production in Escherichia coli
2-keto-3-deoxy-D-arabinoheptulosonate-7-phosphate (DAHP)
acid for animal species and humans, depends largely on
additional nitrogen source was studied: glutamine was not
biosynthesis. We also compared the efficiency of glucose,
Biotransforrnation of chemically synthesized precursors or
both of these processes due to expensive precursors in the
can be used more efficiently than glucose with overexpression
E. coli host cell. While overexpression of AroG alone with
former and low yield in the latter hamper the expected large
found to improve neither plasmid stability, nor tryptophan
glycerol as carbon sources for L-tryptophan biosynthesis.
However, very few attempts were made to optimize precursor
improve the yield in fermentative processes have focused on
in nature as a major component of lignocellulosic biomass,
increased to 14% when xylose was used. In the overexpression
level obtained from TrpAE overexpression only, overexpression
levels in vivo . While investigation along this line was in
market of L-tryptophan. Most of the previous studies to
medium increased by 28% in xylose compared to glucose.
medium. Use of 0.3% xylose+0.7% pyruvic acid and 0.3%
microbial processes due to drawback of chemical synthesis:
negative effect on L-tryptophan biosynthesis in xylose
nitrogen sources are the major microbial production
of TktA together with AroG and TrpAE showed a 90% increase
of TrpAE only, the specific uwtophan concentration in the
of TzpAE only. On the other hand, TktA and AroG can be
over the basal level. The overexpression of neither Pps, nor
overexpressed together with TrpAE to get higher yields of
Overexpression of either AroG or AroG with TktA had a
Pck did not improve Ltryptophan biosynthesis either with
production by fermentation from inexpensive carbon and
progress in our laboratory, positive effects of transketolase
synthase (AroG), TktA, phosphoenolpyruvate carboxykinase
techniques used. Unfortunately, high production costs of
The commercial production of L-uWtophan, an essential ainino
the effects of overexpressing the tryptophan operon (TrpAE),
The experimental yield obtained from glucose, of 10%
the formation of a racemic mixture of DL-tryptophan.
TrpAE improved L-tryptophan biosynthesis 28% over the basal
TrpAE or AroG and TktA. The effect of glutamine as an
tryptophan biosynthesis, in order to optimize production.
tryptophan biosynthesis. We conclude that xylose, abundant
tryptophan where glucose is favored as a carbon source.
varying the specific activity of key enzymes involved in L-
was reported by Draths et. al. In this study, we investigate
xylose, 0.3% xylose+0.7% pyruvic acid and 0.3% xylose+0.7%
xylose+0.7% glycerol as carbon sources did not improve