Fig. 2

Control of redox balance by manipulating endogenous metabolism (a, b) and furnishing heterologous electron sink reactions (c, d). Endogenous NADPH regenerating enzymes of the oxidative pentose phosphate pathway (a) and the ammonia utilization pathway were deleted to reduce XR activity and accordingly develop a lower XR/XDH activity ratio. Surplus NADH was alleviated via NADH oxidase reaction (a) or utilized as a driving force of acetate reduction pathway consisting of acetyl-CoA synthase (ACS) and acetylating acetaldehyde dehydrogenase (AADH) (b). Gene nomenclature: ZWF1 glucose-6-phsophate dehydrogenase, GND1 6-phosphogluconate dehydrogenase, GDH1 NADPH-dependent glutamate dehydrogenase, GDH2 NADH-dependent glutamate dehydrogenase, noxE NADH oxidase from L. lactis, adhE AADH from Escherichia coli