Bar charts showing relative values of the parameters evaluated respect to that of the wild type. Specific glycerol consumed (mmol/g CDW, YG/X rel) in orange; specific ethanol production (mmol ethanol/g CDW, YE/X rel) in green; specific hydrogen production (mmol hydrogen/g CDW, YH2/X rel) in blue and growth rates (µ relative) in grey. Statistically significant P < 0.05 for YH2/X and YG/X parameters and 0.01 for YE/X was used (0 denotes the wild type values). The clear colours represent the relative values at 22 h and the dark colours at 46 h. In the left-hand column are listed the mutant strains assayed in this work and in the right-hand column the metabolic pathways in which each defective mutant strain is involved. LPS lipopolysaccharide, PPP pentose phosphate pathway, TCA tricarboxylic acid.