Phenylalanine products

Wild strains of E. coli are not used for L-phenylalanine production by direct fermentation. 

We can summarise the enzymatic methods of L-phenylalanine production as follows ... 

The elimination of the amino donor, L-aspartic acid, resulted in an almost complete reduction of activity. Neither cell permeabilisation nor cofactor (pyridoxalphosphate) addition were essential for L-phenylalanine production. Maximum conversion yield occurred (100%, 22 g r) when the amino donor concentration was increased. Aspartic add was a superior amino donor to glutamic add 35 g l 1 was used. 

Production of L-phenylalanine proved to be an attractive target for new startup biotechnology companies as well as established companies. However, this opportunity disappeared once the aspartame manufacturers own L-phenylalanine production plant came on stream. 

When an appropriate chiral phosphine ligand and proper reaction conditions are chosen, high enantioselectivity is achieved. If a diphosphine ligand of C2 symmetry is used, two diastereomers of the enamide coordination complex can be produced because the olefin can interact with either the re face or the si face. This interaction leads to enantiomeric phenylalanine products via diastereomeric Rh(III) complexes. The initial substrate-Rh complex formation is reversible, but interconversion of the diastereomeric olefin complexes may occur by an intramolecular mechanism involving an olefin-dissociated, oxygen-coordinated species (18h). Under ordinary conditions, this step has higher activation enthalpies than the subsequent oxidative addition of H2, which is the first... 

Gerigk, M.R., Maass, D., Kreutzer, A., Sprenger, G., Bongaerts, J., Wubbolts, M. and Takors, R. (2002) Enhanced pilot-scale fed-batch L-phenylalanine production with recombinant escherichia coli by fully integrated reactive extraction. Bioprocess and Biosystems Engineering, 25, 43. 

Takors, R. (2004) Model-based analysis and optimization of an ISPR approach using reactive extraction for pilot-scale L-phenylalanine production. Biotechnology... 

In contrast to the various fermentation and bioconversion approaches that have used enzyme stereoselectivity to syntlresize L-phenylalanine as a single isomer, additional methods have been developed that rely on the same stereoselectivity to resolve racemic mixtures of chemically synthesized amino acids. One such general approach, which has been successfully commercialized for L-phenylalanine production, relies on cleavage of the L-isomer of a D,L-a-amino acid amide mixture by an enantiospecific amidase enzyme. The general procedure operated... 

Phenylalanine production from a plasmid harbouring auxotrophic mutant of E. caii has been studied in batch cultures. Phenylalanine is produced in the stationary phase due to the release of feedback inhibition after depletion of tyrosine. The fermentation can be sununarised as ... 

Fig. 15 L-Phenylalanine production using an L-phenylalanine ammonia lyase.

As much as 600000 cycles have been reported for the FDH/formate-driven PEG-NADH-recycling system in the case of L-phenylalanine production (Fig. 2) by reductive amination with phenylalanine dehydrogenase [99]. 

Gerigk, M. et al (2002) Process control for enhanced L-phenylalanine production using different recombinant Escherichia coli strains. Biotechnol. Bioeng., 80, 746-754. 

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