Autor(es):
González-Pajuelo, María 
; Meynial-Salles, Isabelle ; Mendes, Filipa ; Soucaille, Philippe ; Vasconcelos, Isabel
Data: 2006
Identificador Persistente: http://hdl.handle.net/10400.14/6718
Origem: Veritati - Repositório Institucional da Universidade Católica Portuguesa
Descrição
Clostridium acetobutylicum is not able to grow on glycerol as the sole carbon source since it cannot reoxidize
the excess of NADH generated by glycerol catabolism. Nevertheless, when the pSPD5 plasmid, carrying the
NADH-consuming 1,3-propanediol pathway from C. butyricum VPI 3266, was introduced into C. acetobutylicum
DG1, growth on glycerol was achieved, and 1,3-propanediol was produced. In order to compare the physiological
behavior of the recombinant C. acetobutylicum DG1(pSPD5) strain with that of the natural 1,3-
propanediol producer C. butyricum VPI 3266, both strains were grown in chemostat cultures with glycerol as
the sole carbon source. The same “global behavior” was observed for both strains: 1,3-propanediol was the
main fermentation product, and the qH2 flux was very low. However, when looking at key intracellular enzyme
levels, significant differences were observed. Firstly, the pathway for glycerol oxidation was different: C.
butyricum uses a glycerol dehydrogenase and a dihydroxyacetone kinase, while C. acetobutylicum uses a glycerol
kinase and a glycerol-3-phosphate dehydrogenase. Secondly, the electron flow is differentially regulated: (i) in
C. butyricum VPI 3266, the in vitro hydrogenase activity is 10-fold lower than that in C. acetobutylicum
DG1(pSPD5), and (ii) while the ferredoxin-NAD reductase activity is high and the NADH-ferredoxin reductase
activity is low in C. acetobutylicum DG1(pSPD5), the reverse is observed for C. butyricum VPI 3266. Thirdly,
lactate dehydrogenase activity is only detected in the C. acetobutylicum DG1(pSPD5) culture, explaining why
this microorganism produces lactate.
