Screening of L-isoleucine producers among ethionine resistant mutants of L-threonine producing bacteris.

Threonine production by ethionine-resistant mutants of Serratia marcescens.

Ethionine reduced both the growth rate and the final growth level of Serratia marcescens Sr41. Growth inhibition was completely reversed by methionine. Strain D-315, defective in homoserine dehydrogenase I, was more sensitive to ethionine-mediated growth inhibition than was the wild-type strain. Ethionine-resistant mutants were isolated from cultures of strain D-316, which was derived from stra...

Use of Feedback-Resistant Threonine Dehydratases of Corynebacterium glutamicum To Increase Carbon Flux towards l-Isoleucine.

The biosynthesis of l-isoleucine proceeds via a highly regulated reaction sequence connected with l-lysine and l-threonine synthesis. Using defined genetic Corynebacterium glutamicum strains characterized by different fluxes through the homoserine dehydrogenase reaction, we analyzed the influence of four different ilvA alleles (encoding threonine dehydratase) in vectors with two different copy ...

Selection and characterization of L-ethionine resistant mutants of Trichosporon cutaneum.

Trichosporon cutaneum R57 and its L-ethionine resistant mutant NZ94 strain were investigated. The amino acid analyses of cell content of both strains were carried out. The pool of free methionine in the mutant strain is enhanced 16.5 times. The total amount of sulphur-containing amino acids in the mutant cells was significantly increased from 36.8 in the wild strain to 113.4 mg/g protein in the...

The feedback control mechanisms of biosynthetic L-threonine deaminase by L-isoleucine.

Production of L-threonine by auxotrophic mutants of Escherichia coli.

Two auxotrophic mutants of Escherichia coli have been shown to accumulate significant amounts of l-threonine in the culture medium. One mutant, 13071, is deficient in alpha,epsilon-diaminopimelic acid (DAP), and the other, 13070, is deficient in both DAP and methionine. Accumulation of l-threonine by 13071 in a synthetic medium with mannitol as the carbon source at 37 C incubation temperature w...