Characteristics of methionine production by an engineered Corynebacterium glutamicum strain.
A methionine-producing strain was derived from a lysine-producing Corynebacterium glutamicum through a process of genetic manipulation in order to assess its potential to synthesize and accumulate methionine during growth. The strain carries a deregulated hom gene (hom(FBR)) to abolish feedback inhibition of homoserine dehydrogenase by threonine and a deletion of the thrB gene (delta thrB) to abolish threonine synthesis. The constructed C. glutamicum MH20-22B/hom(FBR)/delta thrB strain accumulated 2.9 g/l of methionine by batch fermentation and showed resistance to methionine analogue ethionine at concentrations up to 30 mM. The growth of the strain was apparently impaired as a result of the accumulation of methionine biosynthetic intermediate, homocysteine. Production assays also revealed that the accumulation of methionine in the growth medium was transient and declined as the carbon source was depleted. During the period of methionine disappearance, the methionine biosynthetic genes were completely repressed in the engineered strains but not in the parental strain. After all, we have not only successfully constructed a methionine-producing C. glutamicum strain by genetic manipulation, but also revealed cellular constraints in attaining high yield and productivity.
Park
Soo-Dong
SD
Graduate School of Biotechnology, Korea University, Anam-dong, Sungbuk-ku, Seoul 136-701, Republic of Korea.
Lee
Joo-Young
JY
Sim
Soo-Yeon
SY
Kim
Younhee
Y
Lee
Heung-Shick
HS
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D048230:Corynebacterium glutamicum / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D005001:Ethionine / Q000494:pharmacology; D015964:Gene Expression Regulation, Bacterial; D006710:Homocysteine / Q000378:metabolism; D008239:Lysine / Q000096:biosynthesis / Q000235:genetics; D008715:Methionine / Q000096:biosynthesis* / Q000235:genetics; D009154:Mutation; D013912:Threonine / Q000096:biosynthesis / Q000235:genetics
D001426:Bacterial Proteins; D006710:Homocysteine; D013912:Threonine; D008715:Methionine; D008239:Lysine; D005001:Ethionine