Fig. 1.

(a) Schematic of E working on two complementary substrates A and B to deliver products, e.g., biomass, gases, or water. (b) Schematic for the synthesizing unit (SU) model. (c) Schematic for the additive model, and we note that it ignores the binding order effect on EAB from the binding of A and B to E. (d) Schematic for the Liebig’s law of the minimum (LLM) model, where dashed lines mean the associated substrate is unlimited. The SU model, additive model, and LLM model are approximations to the law of mass action. Forward reaction parameters are designated with superscript “+”, while backward reaction parameters are designated with superscript “−”. The k terms represent rate constants for each reaction in appropriate units.