production potential of iRsp1095 with different carbon sources and glutamate as the nitrogen source. (a)Relationship between growth rate and H2 production. Uptake rates were determined based on a reference chemostat (16 h retention time) fed with succinate (SUR = 1.57 mmol/g DW h) and glutamate (GlUR = 0.75 mmol/g DW h), such that, GlUR was not varied and any other carbon source was supplied by keeping the total number of carbon atoms constant. Experimentally observed H2 flux from the reference chemostat is shown as a data point. Dashed lines indicate the region that represents the suboptimal growth rates at which the theoretical maximum amount of H2 is produced for each carbon source. (b)Relationship between substrate reducing power and electrons used in H2 production (glutamate only case not included). Best fitting lines correspond to three phases of growth in (a) (R2 = 1 in all cases).