Rational design of a Corynebacterium glutamicum pantothenate production strain and its characterization by metabolic flux analysis and genome-wide transcriptional profiling.

A "second-generation" production strain was derived from a Corynebacterium glutamicum pantothenate producer by rational design to assess its potential to synthesize and accumulate the vitamin pantothenate by batch cultivation. The new pantothenate production strain carries a deletion of the ilvA gene to abolish isoleucine synthesis, the promoter down-mutation P-ilvEM3 to attenuate ilvE gene expression and thereby increase ketoisovalerate availability, and two compatible plasmids to overexpress the ilvBNCD genes and duplicated copies of the panBC operon. Production assays in shake flasks revealed that the P-ilvEM3 mutation and the duplication of the panBC operon had cumulative effects on pantothenate production.

Ketopantoate reductase activity is only encoded by ilvC in Corynebacterium glutamicum.

Ketopantoate reductase catalyzes the second step of the pantothenate pathway after ketoisovalerate, common intermediate in valine, leucine and pantothenate biosynthesis. We show here that the Corynebacterium glutamicum ilvC gene is able to complement a ketopantoate reductase deficient Escherichia coli mutant. Thus ilvC, encoding acetohydroxyacid isomeroreductase, involved in the common pathway for branched-chained amino acids, also exhibits ketopantoate reductase activity.