Applicability and generality of ECF. Effect of the number of integrated enzymes and the β factor on the model error profile is investigated for various mutants to demonstrate the applicability of the ECF model with a β factor of 1. (a) ppc(-) knockout mutant, (b) cra(-)knockout mutant, (c) fnr(-) knockout mutant in E. coli. (d) als-overexpressing and pta (-) knockout mutant in B. subtilis. The mean (a1, b1, c1, d1) and relative standard deviation (a2, b2, c2, d2) of the model error are simulated with respect to the number of integrated enzymes when the β factor is changed as 0.5 (yellow), 1 (red), 2 (black), 4 (green).