Fig. 6

The relative flux distribution of the Stickland reactions-coupled methanogenesis, simulated with kinetic parameters under the growth on gelatin of a methanogenic culture (a). A time-scale simulation for calculating an optimized reaction flux rate of the model is shown in b. The predicted flux rate of each reaction is proportional to the relative gradients of the respective reactions. The optimized flux rates for the key reactions involving in methanogenesis from amino acids are represented in c (left). The production rate of methane (R13) was objectively increased under selective constraints of R1 (alanine) and R2/R3 (glycine), which is shown in c. The flux distribution was optimized for a maximal methane rate. Shown are flux values in units of mmol per min per ml. The reaction abbreviations are defined in Additional file 1: Table S1