To smoothen the process of n-butanol formation in Pseudomonas putida
KT2440, detailed knowledge of the impact of this organic solvent on cell
physiology and regulation is of outmost importance. Here, we conducted a
detailed systems biology study to elucidate cellular responses at the
metabolic, proteomic, and transcriptional level. Pseudomonas putida
KT2440 was cultivated in multiple chemostat fermentations using
n-butanol either as sole carbon source or together with glucose.
Pseudomonas putida KT2440 revealed maximum growth rates (mu) of 0.3
h(-1) with n-butanol as sole carbon source and of 0.4 h(-1) using equal
C-molar amounts of glucose and n-butanol. While C-mole specific
substrate consumption and biomass/substrate yields appeared equal at
these growth conditions, the cellular physiology was found to be
substantially different: adenylate energy charge levels of 0.85 were
found when n-butanol served as sole carbon source (similar to glucose as
sole carbon source), but were reduced to 0.4 when n-butanol was
coconsumed at stable growth conditions. Furthermore, characteristic
maintenance parameters changed with increasing n-butanol consumption.
C-13 flux analysis revealed that central metabolism was split into a
glucose-fueled Entner-Doudoroff/pentose-phosphate pathway and an
n-butanol-fueled tricarboxylic acid cycle when both substrates were
coconsumed. With the help of transcriptome and proteome analysis, the
degradation pathway of n-butanol could be unraveled, thus representing
an important basis for rendering P. putida KT2440 from an n-butanol
consumer to a producer in future metabolic engineering studies.