Microbial Conversion of Glycerol to 1,3-Propanediol: Physiological Comparison of a Natural Producer, Clostridium butyricum VPI 3266, and an Engineered Strain, Clostridium acetobutylicum DG1(pSPD5)
Glycerol
0301 basic medicine
0303 health sciences
03 medical and health sciences
Propylene Glycols
Clostridium butyricum
Clostridium acetobutylicum
Gene Expression Regulation, Bacterial
Genetic Engineering
NAD
Culture Media
Plasmids
DOI:
10.1128/aem.72.1.96-101.2006
Publication Date:
2006-01-03T20:33:36Z
AUTHORS (5)
ABSTRACT
ABSTRACT
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 qH
2
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.
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