Metabolic engineering to produce tyrosine or phenylalanine in a tryptophan-producing Corynebacterium glutamicum strain

Article Abstract:

A Corynebacterium glutamicum strain with the ability to overproduce tyrosine and phenylalanine was constructed from a tryptophan-producing strain. The recombinant strains were constructed by introducing three biosynthetic genes desensitized to end product inhibition via multicopy plasmid vectors. The mutant gene for 3-deoxy-D-arabino-heptulosoate 7-phosphate synthase (DS) and chorismate mutase was cloned in pKY1, while pKF1 contained both genes as well as mutant prephenate dehydratase. C. glutamicum transformed with these plasmids increasedaromatic amino acid production by 1.5- to 1.8-fold relative to the original host strain.

Innovations, Microbial genetic engineering, Amino acid metabolism

Hyperproduction of tryptophan by Corynebacterium glutamicum with the modified pentose phosphate pathway

Article Abstract:

A classically derived tryptophan-producing Corynebacterium glutamicum strain was significantly improved by plasmid-mediated amplification of the genes for rate-limiting enzymes in the terminal pathways and by construction of a plasmid stabilization system. Tryptophan yield was improved in the presence of the amplified transketolase gene in the engineered strain of C. glutamicum via low-copy-number plasmids. High-copy-number amplification of the gene resulted in a tryptophan production even lower than that resulting from the absence of the gene.

Genetic aspects, Plasmids, Bacterial genetics, Tryptophan

Mechanism of alanine hyperproduction by Arthrobacter oxydans HAP-1: metabolic shift to fermentation under nongrowth aerobic conditions

Article Abstract:

Arthrobacter oxydans HAP-1 induces hyperproduction of DL-alanine under nongrowth aerobic conditions. L-alanine dehydrogenase undergoes a metabolic shift to a fermentative pathway along with reduced activities of pyruvate dehydrogenase and of the enzyme catalyzing NADH oxidation in the stationary phase. It is suggested that alanine acts as an electron sink even under aerobic conditions, resulting in overproduction of the enzyme.

Enzymes, Fermentation, Glutamate, Protein metabolism, Alanine