Currently the reactions directly encoded by hydG and ech are the only source of molecular hydrogen. Nonetheless, the hydG-ech mutant displayed a hydrogen flux of 0.58 +- 0.06 mmol/gCDW/hr (see flux data set). Considering this data to be reliable, two options remain, either the knock-outs are not 100% effective or unknown hydrogen sources exist in metabolism.
With our current knowledge, the best way to represent this situation is with a hydrogen source, constrained to the highest observed experimental value.
Unfortunately this type of reaction would allow the model to produce hydrogen out of nowhere. This can have an impact in multiple ways, but most significantly the fact that hydrogen is involved in reversible reactions.
Alternatively, the simplification used in previous models was to consider the hydrogen synthesized by hydG-ech to be 0.
Currently the reactions directly encoded by hydG and ech are the only source of molecular hydrogen. Nonetheless, the hydG-ech mutant displayed a hydrogen flux of 0.58 +- 0.06 mmol/gCDW/hr (see flux data set). Considering this data to be reliable, two options remain, either the knock-outs are not 100% effective or unknown hydrogen sources exist in metabolism.
With our current knowledge, the best way to represent this situation is with a hydrogen source, constrained to the highest observed experimental value.
Unfortunately this type of reaction would allow the model to produce hydrogen out of nowhere. This can have an impact in multiple ways, but most significantly the fact that hydrogen is involved in reversible reactions.
Alternatively, the simplification used in previous models was to consider the hydrogen synthesized by hydG-ech to be 0.