Ae. Bainotti et al., KINETIC-STUDIES AND MEDIUM IMPROVEMENT OF GROWTH AND VITAMIN-B-12 PRODUCTION BY ACETOBACTERIUM SP IN BATCH CULTURE, Journal of fermentation and bioengineering, 81(4), 1996, pp. 324-328
Kinetics of inhibition of the growth of Acetobacterium sp. by methanol
(substrate) and acetate (inhibitory end-product) were analyzed using
a second-order substrate inhibition model coupled with a non-competiti
ve product inhibition model. The analysis revealed that the substrate
saturation constant K-s was 83.1 mM methanol; the substrate inhibition
constant K-i was 277.8 mM methanol; the inhibition constant K-p was 0
.835 mM undissociated acetic acid (239 mM of total acetic acid at pH 7
.2); the exponent of inhibition n was 0.72; and mu(max) was 0.175 h(-1
). The growth characteristics of Acetobacterium sp. in a defined mediu
m containing methanol and CO2 were investigated and this medium was mo
dified in order to optimize growth of the bacterium and production of
vitamin B-12 in batch culture. The composition of the modified medium
was as follows (per liter of deionized water): methanol, 8 g; NaHCO3,
15.0 g; KH2PO4, 0.685 g; NH4Cl, 1.0 g; MgSO4 . 7H(2)O, 0.1 g; CoCl2 .
6H(2)O, 0.02 g; 5,6-dimethylbenzimidazole, 0.02 g; yeast extract, 2.0
g; L-cysteine-HCl . H2O, 0.5 g; trace element solution, 80 ml; vitamin
solution, 40 ml; titanium (III) citrate, 0.015 mM. The maximum cell c
oncentration of Acetobacterium sp. doubled (1.3 g/l) when the acetogen
was grown in the modified medium compared with that in the basal medi
um (0.63 g/l).