When glycerol was co-supplied, lactobionic acid biosynthesis
was constrained despite the high cell density conditions achieved.
P. taetrolens was therefore capable of utilizing glycerol in a mixed
carbon source strategy, but only cell biomass formation and
maintenance were promoted. Though glycerol was not readily
assimilated once cell growth ceased, glycerol feeding provided
higher C-source availability and acetyl-CoA pools during lactobionic
acid production. In pseudomonads, glycerol is taken up and
first converted into the central pathway intermediate
D-glyceraldehyde-3-phosphate which is further converted to
glucose-6-phosphate and then channelled into the
Entner-Doudoroff pathway (Lessie and Phibbs, 1984). However,
such increased nutrient and energy conditions did not lead to higher
metabolic activity levels, suggesting likewise that the co-supply of
non-lactose C-sources like glycerol did not lead to the induction of
lactobionic acid biosynthesis.