Electrolyte adjustment to mitigate the local pH changes of enzymes on a porous electrode has been shown as a simple method to maximise the product formation, important for fuel-forming applications. Whilst the precise conditions for each system will depend on the enzyme, current density and electrode architecture, we have demonstrated with the IO electrodes that the following guidelines can be applied to optimise any porous bioelectrochemical system. To achieve this the bulk pH should not be chosen for the 'ideal' enzyme activity pH (determined by solution assay), but so that the local pH changes lead the solution into the optimum range.