Fig. 2.

Optimization of the de novo biosynthesis pathway (Module 1) to enhance the extracellular electron transfer (EET) rate. a A depiction of the de novo biosynthesis pathway of NAD⁺ (Module 1). b Plasmids that included the assemblage of genes (nadA, nadC, and nadB) in Module 1. c Voltage output in microbial fuel cells (MFCs) of the above S. oneidensis recombinant strains. d Quantitative measurements of intracellular NAD⁺, NADH, and total NAD(H/⁺) levels of these strains under anaerobic cultures. The error bars represent the standard deviation from three independent experiments