GLUCOSE METABOLISM IN BATCH AND CONTINUOUS CULTURES OF GLUCONACETOBACTER DIAZOTROPHICUS

LUNA MARIA FLAVIA; GALAR MARIA LINA; BOIARDI JOSE LUIS

CURRENT MICROBIOLOGY

SPRINGER

Lugar: NEW YORK; Año: 2006 vol. 52 p. 163 - 168

0343-8651

Periplasmic glucose oxidation (via a PQQ-linked glucose dehydrogenase, PQQ-GDH) was observed in continuous cultures of G. diazotrophicus regardless the carbon source (glucose or gluconate) and the nitrogen source (N2 or NH3). Its synthesis was stimulated by conditions of high energetic demand (i.e. N2-fixation) and/or C-limitation. Under C-excess conditions PQQ-GDH synthesis increased with the glucose concentration in the culture medium. In batch cultures PQQ-GDH was actively expressed in very early stages with higher activities under conditions of N2-fixation. Hexokinase activity was almost absent under any culture condition. Cytoplasmic NAD-linked glucose dehydrogenase (NAD-GDH) was expressed in continuous cultures under all tested conditions and its synthesis increased with the glucose concentration. On the other hand low activities of this enzyme were detected in batch cultures. Extracellular oxidation, via PQQ-GDH, seems to be the principal pathway for metabolism of glucose in G. diazotrophicus and NAD-GDH an alternative route under certain environmental conditions.