Threonine, improved production

Recombinant DNA techniques were employed to improve the L-threonine producer. A threonine-deficient mutant of E. coli was transformed by the genes of threonine operon obtained from a-amino-/ -hydroxyvaleric acid (AHV)-resistant and feedback-insensitive mutants to amplify the expression of enzymes and to increase the amount of L-threonine. E. coli mutant strain was also constructed to have amplified genes of threonine operon obtained from AHV-resistant and feedback-insensitive mutant by the action of Mu phage on the chromosomal DNA. This strain is used in France in the practical production of L-threonine. The productivity of bacterial strains developed as the L-threonine producer is summarized in Table 2 [14]. L-Threonine hyperproducing E. coli mutant, which can produce 100 g/1 of L-threonine in 77 h, was constructed by Okamoto et al. who suggested that the strain has some impairment in L-threo-nine uptake function [15]. 

Ketone donors bearing a-heteroatoms are particularly useful donors for the enamine-catalyzed aldol reactions (Scheme 18). Both anti and syn aldol products can be accessed in remarkably high enantioselectivities using either proline or proline-derived amide, sulfonamide, or peptide catalysts. The syn selective variant of this reaction was discovered by Barbas [179]. Very recently, Luo and Cheng have also described a syn selective variant with dihydroxyacetone donors [201], and the Barbas group has developed improved threonine-derived catalysts 71 (Scheme 18) for syn selective reactions with both protected and unprotected dihydroxyacetone [202]. 

E. coli The effect of biotin and air condition on L-threonine production was investigated Supply of biotin and oxygen-enriched air improved 80.2 Lee et al. [52]... 

Ishida M, Kawashima H, Sato K et al (1994) Factors improving L-threonine production by a three L-threonine biosynthetic genes-amplified recombinant strain of Brevibacterium lacto-fermentum. Biosci Biotech Biochem 58 768-770... 

Shimizu E, Oosumi T, Heima H et al (1995) Culture conditions for improvement of L-threonine production using a genetically self-cloned L-threonine hyperproducing strain of Escherichia coli K-12. Biosci Biotech Biochem 59 1095-1098... 

Masuda M, Takamatsu S, Nishimura N et al (1992) Improvement of nitrogen supply for L-threonine production by a recombinant strain of Serratia marcescens. Appl Biochem Biotechnol 37 255-265... 

Lee MH, Lee HW, Park JH et al (2006) Improved L-threonine production of Escherichia coli mutant by optimization of culture conditions. J Biosci Bioeng 101 127-130... 

The principle of mutation to feedback resistance was recently combined with that of reducing end product concentration in the development of an improved threonine fermentation. Shiio and Naka-mori (1969) isolated a threonine-excreting (1.9 g/liter) mutant of E. coli... 

Azetidinyl-4-ketones are closer than azetidinyl-4-carboxylic esters to the target 4-acyloxy derivatives 11, 29, 36. Thus, Hanessian s version of the threonine route [29], utilizing a-keto anions, can be considered an improvement over Shiozaki s a-carboxyanion strategy, especially when its aptitude for being scaled-up for industrial production is considered. The key-step, cyclization of amide 68a (prepared from epoxyacid 64 and fV-anisylphenacylamine) to azeti-dinone 28a, is carried out by simple treatment with K2CO3 at ambient temperature silylation, CAN-mediated cleavage and oxidation with mono-perphthalic acid complete the sequence to synthon 29b. 

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