Dynamics in different purine nucleotide ratios. Dynamics in A) the adenylate energy charge, B) the guanylate energy charge, C) the GTP/GMP ratio and D) the GTP/GDP ratio during anaerobic batch fermentation of 20 g/L glucose and 40 g/L xylose using strains TMB3057 (XR/XDH, white markers) and TMB3359 (XI, black markers). The adenylate energy charge and the guanylate energy charge were calculated according to (ATP + ½ADP)/(ATP + ADP + AMP) and (GTP + ½GDP)/(GTP + GDP + GMP) , respectively. Errors are given as 95% confidence intervals of the means calculated from duplicate experiments for each strain (5 ≤ n ≤ 11). The shaded area indicates the period until glucose depletion.