Fig. 2.

End-products of glucose metabolism in 2,3-BD producers and control strains under oxygen limiting conditions: 25 mL of cell suspension in stoppered 50-mL flasks incubated with 2 % (wt/vol) glucose for 48 h at 180 rpm and 30 °C. Control strains produced optically active 2,3-BD (most likely (2S,3S)-2,3-BD), while the engineered strains produced meso-2,3-BD. For simplicity, a single color is used to represent any form of 2,3-BD. Lactate dehydrogenase negative strains (a) grown on glucose (left) and acetate (right); triple deletion mutants C. glutamicum ΔaceEΔpqoΔldhA(pEKEx2-als,aldB,butA), C. glutamicum ΔaceEΔpqoΔldhA(pEKEx2-als,aldB, _Ptuf butA) (b) and quadruple deletion mutants C. glutamicum ΔaceEΔpqoΔldhAΔmdh(pEKEx2-als,aldB,butA) and C. glutamicum ΔaceEΔpqoΔldhAΔmdh(pEKEx2-als,aldB, _Ptuf butA) (c). red 2,3-BD; blue acetoin; magenta acetolactate; light green succinate; purple acetate; brown pyruvate; dark green α-ketoisovalerate; black DHA; dark grey glycerol; yellow l-alanine