EVALUATION OF CONTINUOUS CHEMOSTAT CULTIVATION OF THIOBACILLUS FERROOXIDANS ON FERROUS IRON OR TETRATHIONATE

Abstract

Thiobacillus ferrooxidans was cultured in continuous flow chemostats on FeSO, at pHl.6 and K was subject to one or other of non-competitive product inhibition (NCP1) or 254% at pH2.5. On iron as the limiting substrate, growth predominatly competitive product inhibition (PCP1). This resulted in premature washout at dilution rates dependent on the concentration of FeSO, in the medium feed. Growth yield, apparent maintenance energy requirement and maximum specific growth rate ae were determined over a wide range of dilution rates for cultures subject to either NCPl or PCP1l. With tetrathionate as the limiting substrate no inhibition effects were observed in the chemostat pH2.5, although tetrathionate is an inhibitory substrate at some pH values. Yield, apparent maintenance and ee page eater For both substrates, true growth yield, Yo (g dry wt per g atom Fe or g mole KS 96 oxidized) was determined from the experimental data and enabled calculation 24 of the Yarp (g dry wt per mole ATP available from each substrate) and the probable ° + ° : . . . ATP requirement for NAD reduction during iron oxidation.