The strain in which GSU1497 was deleted had maximal current production that was 2/3rds that of wild type (Table 4), but took 5 times longer to reach its maximum than wild-type cells.
The maximum power and current production in the presence of Acetaminophen and Bismuth as novel cathodic mediators was 2.55 × 10−5 W, 1.29 × 10−5 A, 2.9 × 10−5 W and 1.75 × 10−4 A, respectively.
The electrochemical tests showed that the stack exhibited a high hydrogen production efficiency with a maximum current efficiency of 95.3% for hydrogen production and a hydrogen evolution amount per unit input electrical energy of 259.1 mL/W h at 0.2 C.
However, since the maximum B value could not exceed 57%, it is indicated that MET could not liberate the maximum metabolic capability of the cell for growth-coupled current production.
Turning now to flavin-based current production, Figure 3 indicates that, to liberate the maximum capability of the flavin production, the Shewanella strain needs to reduce the biomass production rate to a very low level and increase the reduced cytochrome c production rate to about 30 mmol/gDW/h.
Such novel anodic architecture (organic binder free) presents an excellent electro-chemical performance, with a maximum current density of 700 mA cm−2 at 1.3 V, and, concomitantly, a large H2 production rate with low energy requirement compared to water electrolysis.
The production cost can be minimized, if the cell module is operated with the minimum voltage at maximum current density.
In summary, in addition to providing further circumstantial evidence for the importance of microbial nanowires in high-density current production, this study provides several lines of evidence, which suggest that G. sulfurreducens requires OmcZ for maximum power production.
Therefore, studying the current production in MFCs linked to the NADH/NAD+ cycle could be considered as a way to probe the maximum metabolic potential for ideal electricity generation.
