Fig. 1

Designed IPA production pathway and NADPH supply. A Pathway for the synthesis of IPA from sugars and gaseous substrates. A key intermediate, acetyl-CoA, was processed by heterologously expressed enzymes for acetone synthesis (blue color) and Sadh (red color). Acetate, provided by the native pathway, was used to receive CoA from acetoacetyl-CoA. One of the genes, pduL2, in the acetate pathway was disrupted to enhance the carbon flow to IPA. One molecule of NADPH is required to convert acetone into IPA. Thl, thiolase; CtfAB, CoA transferase; Adc, acetoacetate decarboxylase; PduL1 and PduL2, phosphotransacetylase; Ack, acetate kinase. B NADPH supply using reducing equivalents derived from sugar metabolism. The sugar metabolism provided reduced form of ferredoxin (Fd²⁻) and NADH. The NfnAB complex transferred electrons from Fd²⁻ and NADH to NADP⁺, simultaneously. C In the presence of H₂, NADPH was formed via two pathways. One was via Fd²⁻ and NADH. The HydABC complex transferred electrons from H₂ to Fd and NAD⁺, followed by the transfer by NfnAB complex. The other pathway was a direct electron transfer from H₂ to NADP⁺