Mf. Serrano et al., Culture of Azetobacter vinelandii with acetate as carbon source under oxygen limitated conditions, AFINIDAD, 57(487), 2000, pp. 167-174
We studied discontinuous and fed-batch cultures of Azotobacter vinelandii o
n acetate under oxygen limitation conditions, with the intention of using t
hem as a Model System for the experimental study of oxygen transfer intensi
fication methods in aerobic fermenters. Using a discontinuous culture, thre
e series of experiments were carried out: one under the simplest conditions
for the application of this system to an aerobic fermenter, with no pH con
trol and under atmospheric nitrogen-fixing conditions; the other two series
were performed with pH control and under atmospheric nitrogen-fixing condi
tions and with NH4Cl as the nitrogen source, respectively. We determined th
e overall kinetic parameters for both exponential growth and linear growth
(with oxygen limitation). An increase in the stirring speed did'nt have inf
luence on the specific growth rate but produced a higher specific oxygen an
d carbon source consumption rate. The nitrogen source was also seen to have
an evident influence on the specific rate of consumption of the substrate,
which was greater under nitrogen-fixing conditions. As regards the specifi
c growth rate, A. vinelandii seems to prefer acetate to glucose and ammonia
to atmospheric nitrogen.
In a fed-batch culture, i.e. a discontinuous culture with acetate as the ca
rbon source and using a concentrated solution of acetic acid to keep pH lev
els constant, two series of experiments were carried out. As the concentrat
ion of the carbon source was kept constant, we were able to analyse, indepe
ndently, the damage suffered by the microorganism as it grew during variabl
e time periods under oxygen limitation conditions. There was seen to be a d
iminution of mu when growth time under oxygen limitation conitions was incr
eased.