Intracellular precursor supply is a critical factor for amino acid productivity of
Corynebacterium glutamicum. To test for the effect of improved pyruvate availability on
l-lysine production, we deleted the
aceE gene encoding the E1p enzyme of the pyruvate dehydrogenase complex (PDHC) in the
l-lysine-producer
C. glutamicum DM1729 and characterised the resulting strain DM1729-BB1 for growth and
l-lysine production. Compared to the host strain,
C. glutamicum DM1729-BB1 showed no PDHC activity, was acetate auxotrophic and, after complete consumption of the available carbon sources
glucose and acetate, showed a more than 50% lower substrate-specific biomass yield (0.14 vs 0.33 mol C/mol C), an about fourfold
higher biomass-specific
l-lysine yield (5.27 vs 1.23 mmol/g cell dry weight) and a more than 40% higher substrate-specific
l-lysine yield (0.13 vs 0.09 mol C/mol C). Overexpression of the pyruvate carboxylase or diaminopimelate dehydrogenase genes
in
C. glutamicum DM1729-BB1 resulted in a further increase in the biomass-specific
l-lysine yield by 6 and 56%, respectively. In addition to
l-lysine, significant amounts of pyruvate,
l-alanine and
l-valine were produced by
C. glutamicum DM1729-BB1 and its derivatives, suggesting a surplus of precursor availability and a further potential to improve
l-lysine production by engineering the
l-lysine biosynthetic pathway.
This study is dedicated to Prof. Dr. Hermann Sahm on the occasion of his 65th birthday.
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