Fig. 8

Metabolic flux analysis of l-lysine biosynthesis in B. amyloliquefaciens NCC 156 (yellow) and L. paracasei subsp. paracasei NCC 2511 (blue) during chickpea milk fermentation. The carbon flux through of l-lysine biosynthesis was investigated by monitoring the incorporation of ¹³C from [¹³C₄] l-aspartate, added as a tracer to the medium, into l-lysine. As a control, naturally labelled l-aspartate was supplemented to the same amount instead. The data show the ¹³C enrichment in total l-lysine, free extracellular l-lysine, and total l-aspartate after 20 h of fermentation, measured by GC/MS. The given summed fractional labelling (SFL) reflects the average enrichment of ¹³C in each of the analytes. The corresponding values from the control experiment for total l-aspartate (1.1 ± 0.1%), total l-lysine (1.1 ± 0.1%), and free extracellular l-lysine (1.1 ± 0.1%) matched the theoretical values expected from natural ¹³C abundance. They are shown as dashed lines. The significance of ¹³C enrichment in each analyte was determined by comparison of the measured value against the naturally labelled control, and is marked accordingly (*p < 0.05, **p < 0.01). n = 3