Kinetic Studies and Medium Improvement of Growth and Vitamin B_<12> Production by Acetobacterium sp. in Batch Culture

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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-competitive 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 μ_<max> was 0.175 h^<-1>. The growth characteristics of Acetobacterium sp. in a defined medium containing methanol and CO_2 were investigated and this medium was modified 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; NaHCO_3,15.0 g; KH_2PO_4,0.685 g; NH_4Cl, 1.0 g; MgSO_4・7H_2O, 0.1 g; CoCl_2・6H_2O, 0.02 g; 5,6-dimethylbenzimidazole, 0.02 g; yeast extract, 2.0 g; L-cysteine-HCl・H_2O, 0.5 g; trace element solution, 80 ml; vitamin solution, 40 ml; titanium (III) citrate, 0.015 mM. The maximum cell concentration of Acetobacterium sp. doubled (1.3 g/l) when the acetogen was grown in the modified medium compared with that in the basal medium (0.63 g/l).
社団法人日本生物工学会の論文
1996-04-25