KINETICS AND ENERGETICS OF ACETOBACTERIUM SP. IN CHEMOSTAT CULTURE ONMETHANOL-CO2

The kinetics and energetics of Acetobacterium sp. for growth and vitam in B-12 production were analyzed in chemostat cultures on a methanol-C O2 medium under various pHs, methanol concentrations and dilution rate s. The optimal pH was between 6.7 and 6.9. The maximum volumetric rate s of cell, acetate and vitamin B-12 production and methanol consumptio n were 0.06 g.l(-1).h(-1) for cell, 5.7 mmol.l(-1).h(-1) for acetate, 0.27 mg.l(-1).h(-1) for vitamin B-12 and 10 mmol.l(-1).h(-1) for metha nol. The specific production rates of acetate and vitamin B-12 were as sociated with the specific growth rate. Analysis of energetics reveale d that the true growth yield, Y-EG, was 8.14 g cell.(mol methanol cata bolized)(-1) and the maintenance coefficient, m, was 0.479 mmol methan ol catabolized.(g cell)(-1).h(-1). Based on the mass balances with res pect to carbon and electron recovery for methanol consumed, the follow ing reaction stoichiometry was obtained: 4CH(3)OH+ 2CO(2)-->2.34CH(3)C OOH + 0.86 cell C. The conversion ratio of methanol to cell was about 16%. Finally, we offer a simple explanation for the bioenergetics of t his bacterium, suggesting that Y-ATP can be calculated directly from t he values of Y-X/P.